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The aim of this study was to examine the feasibility of cognitive assessment from pre-surgery through two-year follow-up in a sample of pediatric brain tumor (BT) patients. We sought to investigate cognitive function over the course of diagnosis and treatment, and as a function of presenting problems, tumor location, treatment type, and tumor severity. Using a prospective, longitudinal design, standardized IQ measures were administered to pediatric BT patients (ages 6-16) prior to surgery (n=25), 6 months post-diagnosis (n=24), and 24 months post-diagnosis (n=23). Group differences emerged based on tumor severity and treatment type at multiple time points, including prior to surgical intervention; children with high grade tumors performed more poorly than children with low grade tumors, and children receiving surgery plus adjuvant therapy performed more poorly than children who received surgery only. When considered together, an analysis of covariance demonstrated that tumor grade significantly accounted for variability in cognitive functioning, while treatment type did not. Although there is overlap clinically between tumor severity and treatment received, results suggest that tumor severity is an important factor contributing to variability in cognitive functioning and should also be considered when monitoring risk for cognitive deficits in children diagnosed with BT.

After treatment, pediatric brain tumor survivors (PBTS) face emotional and behavioral challenges, perhaps due to tumor or treatment-related changes in brain structures involved in emotion regulation, including those with fronto-limbic connections. We hypothesized that relative to healthy controls (HCs), PBTS would exhibit greater difficulties with behavior and emotional functioning, and display reduced mean fractional anisotropy (mFA) in white matter tracts with fronto-limbic connections including the cingulum bundle (CB), inferior fronto-occipital fasciculus (IFOF), and uncinate fasciculus (UF). We further predicted that mFA would account for variance in the relationship between group and emotional/behavioral outcome. Eleven 8–16 year old PBTS and 14 HCs underwent MRI, including diffusion tensor imaging to assess white matter microstructure. Tractography quantified mFA of selected tracts. Parents rated children’s emotional and behavioral functioning. Compared to HCs, caregivers of PBTS reported poorer behavioral regulation and greater internalizing and externalizing symptoms. Relative to HCs, PBTS had lower mFA within the bilateral CB, IFOF, and UF (ds = 0.59–1.15). Across groups, several medium-to-large correlations linked tract mFA and increased internalizing, externalizing, and poor behavioral regulation. Tract mFA also accounted for significant variance in the group-outcome association. Reduced mFA in fronto-limbic associated tracts may be associated with reduced behavioral regulation following pediatric brain tumor. PBTS with treatment known to impact white matter may be most susceptible. Research with larger, longitudinal samples should clarify this relationship, allow for multiple mediators across time, and consider factors like tumor and treatment type.

BACKGROUND The role of local analgesics for lumbar punctures (LPs) in pediatric oncology patients has not been specifically studied. AIM To compare the efficacy of eutectic mixture of local anesthetics (EMLA) cream to 1% lidocaine injection for LPs. METHOD This was a retrospective observational study of all patients receiving either EMLA cream (EMLA group) or 1% lidocaine subcutaneous injection (lidocaine group) in addition to fentanyl and propofol for LPs over 18 months. Demographics, vital parameters, procedural and recovery times, propofol and fentanyl doses, and adverse events were studied. RESULTS Two hundred ninety LPs in 49 children were studied: 148 in the EMLA group and 142 in the lidocaine group. There was no difference in demographics or preprocedural parameters between the two groups. LPs in the EMLA group were completed in a shorter time (7.5 minutes [CI 7.0-8.1] vs 9.4 minutes [CI 8.9-9.9]) with a faster recovery time (38.7 minutes [CI 36.9-40.9] vs 43.9 minutes. [CI 41.9-45.9]) as compared with the lidocaine group (P

The purpose of this study was to determine associations among neurocognitive outcomes and white matter integrity in the inferior fronto-occipital fasciculus (IFOF), uncinate fasciculus (UF), and genu of the corpus callosum (gCC) in survivors of pediatric brain tumor and healthy controls (HCs). Eleven survivors (ages 8-16;2 years post-treatment) and 14 HCs underwent MRI; diffusion tensor imaging tractography (DSI Studio) was used to assess white matter integrity. Participants completed neuropsychological assessment of overall cognitive ability, executive function, processing speed, divided attention, and memory. As previously reported, survivors performed significantly worse than HCs on measures of overall IQ, working memory, processing speed, and executive function (

The clinical and laboratory features of hemophagocytic lymphohistiocytosis (HLH) are nonspecific that makes the definitive diagnosis of HLH very challenging. The disease is almost universally fatal in the absence of early recognition and appropriate therapy. Elevated serum ferritin level is one of the diagnostic markers of HLH disease. We report the value of testing serum ferritin level early in the disease process in 3 pediatric patients who presented with persistent fever and sepsis-like features. Detection of elevated serum ferritin levels facilitated further testing to confirm the diagnosis of HLH and initiate early therapy with good outcomes.

Congenital brain tumors are rare, representing

Pediatric brain tumors are the second most common cancer diagnosis in individuals under age 20 and research has documented significant neurocognitive, psychosocial, and emotional late effects. Associations among these deficits have not been adequately considered and the role of survivors' coping with stress in relation to deficits is unknown. Further, research has yet to examine neurobiological processes related to neurocognitive, psychosocial, and emotional difficulties in survivors through the use of functional neuroimaging.Questionnaire measures and functional neuroimaging were used to examine the neurocognitive, psychosocial, and emotional functioning and coping responses of survivors of pediatric brain tumors (N = 17; age 8-16) and healthy children (N = 15).Survivors experienced elevated levels of psychosocial and behavioral/emotional difficulties relative to healthy controls and normative data. Increases in brain activation in prefrontal and other anterior regions in response to a working memory task were associated with better psychosocial functioning, use of engagement coping strategies, and less use of disengagement coping strategies. Regression analyses suggest coping accounts for a significant portion of the association between brain activation and behavioral/emotional functioning.This study extends late-effects research by examining neurobiological processes associated with psychosocial and emotional difficulties. These findings contribute to our understanding of difficulties in survivors and provide a foundation for research exploring these associations and mediators of deficits in future longitudinal studies.

The prognosis of diffuse intrinsic pontine glioma (DIPG) remains poor, with no drug proven to be effective.Patients with clinically and radiologically confirmed, centrally reviewed DIPG, who had failed standard first-line therapy were eligible for this multicenter phase II trial. The anti-epidermal growth factor receptor (EGFR) antibody, nimotuzumab (150 mg/m(2)), was administered intravenously once weekly from weeks 1 to 7 and once every 2 weeks from weeks 8 to 18. Response evaluation was based on clinical and MRI assessments. Patients with partial response (PR) or stable disease (SD) were allowed to continue nimotuzumab.Forty-four patients received at least one dose of nimotuzumab (male/female, 20/24; median age, 6.0 years; range, 3.0-17.0 years). All had received prior radiotherapy. Treatment was well tolerated. Eighteen children experienced serious adverse events (SAEs). The majority of SAEs were associated with disease progression. Nineteen patients completed 8 weeks (W8) of treatment: There were 2 PRs, 6 SDs, and 11 progressions. Five patients completed 18 weeks (W18) of treatment: 1 of 2 patients with PR at W8 remained in PR at W18, and 3 of 6 children with SD at W8 maintained SD at W18. Time to progression following initiation of nimotuzumab for the 4 patients with SD or better at W18 was 119, 157, 182 and 335 days, respectively. Median survival time was 3.2 months. Two patients lived 663 and 481 days from the start of nimotuzumab.Modest activity of nimotuzumab in DIPG, which has been shown previously, was confirmed: A small subset of DIPG patients appeared to benefit from anti-EGFR antibody treatment.

Individuals harboring germ-line DICER1 mutations are predisposed to a rare cancer syndrome, the DICER1 Syndrome or pleuropulmonary blastoma-familial tumor and dysplasia syndrome [online Mendelian inheritance in man (OMIM) #601200]. In addition, specific somatic mutations in the DICER1 RNase III catalytic domain have been identified in several DICER1-associated tumor types. Pituitary blastoma (PitB) was identified as a distinct entity in 2008, and is a very rare, potentially lethal early childhood tumor of the pituitary gland. Since the discovery by our team of an inherited mutation in DICER1 in a child with PitB in 2011, we have identified 12 additional PitB cases. We aimed to determine the contribution of germ-line and somatic DICER1 mutations to PitB. We hypothesized that PitB is a pathognomonic feature of a germ-line DICER1 mutation and that each PitB will harbor a second somatic mutation in DICER1. Lymphocyte or saliva DNA samples ascertained from ten infants with PitB were screened and nine were found to harbor a heterozygous germ-line DICER1 mutation. We identified additional DICER1 mutations in nine of ten tested PitB tumor samples, eight of which were confirmed to be somatic in origin. Seven of these mutations occurred within the RNase IIIb catalytic domain, a domain essential to the generation of 5p miRNAs from the 5' arm of miRNA-precursors. Germ-line DICER1 mutations are a major contributor to PitB. Second somatic DICER1 "hits" occurring within the RNase IIIb domain also appear to be critical in PitB pathogenesis.

Recurrent diffuse intrinsic pontine gliomas (DIPG) are traditionally treated with palliative care since no effective treatments have been described for these tumors. Recently, clinical studies have been emerging, and individualized treatment is attempted more frequently. However, an informative way to compare the treatment outcomes has not been established, and historical control data are missing for recurrent disease. We conducted a retrospective chart review of patients with recurrent DIPG treated between 1998 and 2010. Response progression-free survival and possible influencing factors were evaluated. Thirty-one patients were identified who were treated in 61 treatment attempts using 26 treatment elements in 31 different regimens. The most frequently used drugs were etoposide (14), bevacizumab (13), irinotecan (13), nimotuzumab (13), and valproic acid (13). Seven patients had repeat radiation therapy to the primary tumor. Response was recorded after 58 treatment attempts and was comprised of 0 treatment attempts with complete responses, 7 with partial responses, 20 with stable diseases, and 31 with progressive diseases The median progression-free survival after treatment start was 0.16 years (2 months) and was found to be correlated to the prior time to progression but not to the number of previous treatment attempts. Repeat radiation resulted in the highest response rates (4/7), and the longest progression-free survival. These data provide a basis to plan future clinical trials for recurrent DIPG. Repeat radiation therapy should be tested in a prospective clinical study.

Adult-type sarcomas are, as the name indicates, rare tumors in the pediatric population. Although soft tissue sarcomas as a group are not uncommon diagnoses, nonrhabdomyosarcoma soft tissue sarcomas are much rarer and encompass a wide range of diagnoses. A few of these tumors are commonly found in the adult population and are thus referred to as adult-type sarcomas. We present a case of a pleomorphic liposarcoma, an adult-type sarcoma, arising as a primary tumor in the orbit of an 8-year-old boy. The histologic analysis revealed bizarre tumor giant cells and definitive lipoblastic differentiation. The atypical cells were positive for S100, and negative for CD34, desmin, MyoD1, and myogenin. This is a high-grade sarcoma, very rarely encountered in the pediatric population. We present the histologic findings of this unusual pediatric sarcoma and review the literature.

Purpose To determine the dose of cetuximab that can be safely combined with irinotecan for treatment of pediatric and adolescent patients with refractory solid tumors. Patients and Methods This open-label, phase I study enrolled patients ages 1 to 18 years with advanced refractory solid tumors, including tumors of the CNS. Patient cohorts by age group (children, ages 1 to 12 years; adolescents, ages 13 to 18 years) received escalating weekly doses of cetuximab (75, 150, 250 mg/m2) in a 3 + 3 design, plus irinotecan (16 or 20 mg/m2/d) for 5 days for 2 consecutive weeks every 21 days. The primary end points were establishing the maximum-tolerated dose (MTD), recommended phase II dose (RPIID), and pharmacokinetics of the combination. Preliminary safety and efficacy data were also collected. Results Twenty-seven children and 19 adolescents received a median of 7.1 and 6.0 weeks of cetuximab therapy, respectively. Cetuximab 250 mg/m2 weekly plus irinotecan 16 mg/m2/d (pediatric) or 20 mg/m2/d (adolescent) have been established as the MTD/RPIID. Dose-limiting toxicities included diarrhea and neutropenia. Mild to moderate (grade 1 to 2) acneiform rash occurred in a majority of patients; no grade 3 to 4 rashes were observed. Cetuximab demonstrated dose-dependent clearance in both children and adolescents, similar to that in adults. There were two confirmed partial responses, both in patients with CNS tumors. Stable disease was achieved in 18 patients overall, including 10 patients with CNS tumors (38.5%). Conclusion The cetuximab/irinotecan combination can be given safely to children and adolescents with cancer. Promising activity, particularly in CNS tumors, warrants phase II evaluation of this regimen.

Background A Phase II trial was developed to determine the efficacy and toxicity of intravenous vinorelbine, a semi-synthetic vinca alkaloid, in children, adolescent, and young adults with recurrent or refractory solid malignancies.

Positron emission tomography using F-flurodeoxyglucose (FDG-PET) is considered an excellent tool for staging and monitoring disease status in adults with lymphoma. We retrospectively reviewed results of PET/CT and diagnostic computed tomography (CT) scans performed during follow-up after completion of therapy in 41 children

Background The objectives of this study were to determine the maximum tolerated dose (MTD), dose-limiting toxicities (DLTs), pharmacokinetics, and anti-tumor effect of irinotecan in pediatric patients with recurrent or refractory malignancies. Procedure Twenty-three patients between 1 and 21 years of age, with a solid tumor refractory to standard therapy or for which there was no standard therapy were enrolled. Irinotecan was administered over 90 min weekly 4×, every 6 weeks. The initial dose level was 125 mg/m2/day, with subsequent escalations to 160 and 200 mg/m2/day. A MTD was defined in heavily-pretreated and less-heavily-pretreated (≤2 prior chemotherapy regimens, no prior bone marrow transplantation, and no central axis radiation) patients. Pharmacokinetic studies were also performed. Results Neutropenia and diarrhea were the DLTs in heavily pretreated patients; the MTD was 125 mg/m2/day. Neutropenia was the DLT in less-heavily pretreated; the MTD was 160 mg/m2/day. Five patients had stable disease for two to four cycles including one patient each with rhabdomyosarcoma, Ewing sarcoma, neuroblastoma, and two patients with ependymoma. Irinotecan clearance was greater that that previously reported for children receiving high dose irinotecan. Conclusions The recommended phase II dose of irinotecan administered weekly 4×, every 6 weeks in children with solid tumors is 125 mg/m2/dose for heavily pretreated patients and 160 mg/m2/dose for less heavily pretreated patients. © 2005 Wiley-Liss, Inc.

Purpose Tumor growth and metastasis is believed to depend on the tumor's ability to induce neovascularization. Recent studies have indicated that thalidomide inhibits angiogenesis. We performed a phase I and pharmacokinetic study of thalidomide with carboplatin in children with refractory solid tumors. Patients and Methods Carboplatin was administered as a single intravenous dose once every 21 days at a target area under the concentration-time curve of 6 mg/mL·min. Thalidomide was administered daily by mouth. The initial dose level was 100 mg/m2/d with intrapatient dose escalation to a maximum dose of 300 mg/m2/d. The next cohort of patients started at a dose of 300 mg/m2/d, with intrapatient dose escalation to a maximum dose of 500 mg/m2/d. Standard response and adverse event criteria were used. Serial blood samples for thalidomide pharmacokinetics studies were obtained after the first dose. Results Twenty-two patients received 56 cycles of therapy. The maximum tolerated thalidomide dose was 400 mg/m2/d. The dose-limiting toxicity was somnolence. There were no objective responses. Thalidomide's apparent clearance was 55 ± 16 mL/min/m2 and the terminal half-life was 5.9 ± 2.8 hours. There was no evidence of dose-dependent pharmacokinetics in the narrow range studied. Conclusion Thalidomide at a dose of 400 mg/m2/d can be safely administered to children with solid tumors in combination with carboplatin. Somnolence is the major toxicity. In addition, we have characterized the pharmacokinetic behavior of thalidomide in children. This study can serve as the basis for future investigation of thalidomide as an anticancer agent in children.

BACKGROUND Fever and neutropenia (F&N) is a common complication of cancer chemotherapy. It is conveniently managed by hospitalization and empiric administration of parenteral antibiotics. This study attempted to determine whether pediatric cancer patients with F&N identified as low risk for morbidity and mortality by clinical criteria at the time of presentation could be treated safely as outpatients. METHODS Seventy-three episodes of F&N in 41 patients were studied prospectively over 2 years. Eligibility criteria included age ≥2 years, reliable caretakers, and residence within 1 hour of the hospital. Exclusion criteria included hemodynamic instability, dehydration, severe mucositis, pneumonia, leukemia/lymphoma induction therapy, bone marrow transplantation, or other serious comorbidity. Patients were evaluated, received a single dose of intravenous ceftazidime, and were observed for 3–16 hours. They were randomized to receive either oral ciprofloxacin or intravenous ceftazidime as outpatients. Patients were seen daily until they had been afebrile for at least 48 hours and had a rising absolute phagocyte count of >500 cells/μL. RESULTS Sixty-three of 73 episodes (86%) were successfully managed on an outpatient basis. For 31 of 33 episodes in the ceftazidime arm, the patients remained outpatients, compared with 32 of 40 in the ciprofloxacin arm; this difference was not statistically significant. On average, patients remained febrile for 2.7 days and were treated for 4.7 days. Seventy-seven percent of episodes required no modification of initial antibiotic therapy. Of the 10 patients who were hospitalized, 4 had prolonged fever and 3 had emesis. Protracted neutropenia was associated with the need for hospitalization. There were no deaths, intensive care unit transfers, or serious complications. CONCLUSIONS Carefully selected low risk children with fever and neutropenia can be treated safely as outpatients. Close daily medical scrutiny is required. Cancer 1999;86:126–34. © 1999 American Cancer Society.

BACKGROUND An excess risk of second malignancies has been reported in survivors of Ewing's sarcoma. We examined a multiinstitutional data base to reevaluate the risk among survivors of Ewing's sarcoma and to identify possible causal factors. METHODS Information was derived from a data base that included 266 survivors of Ewing's sarcoma. Cumulative incidence rates of second malignancies were calculated. Contributions of clinical features, type and dose of chemotherapy, and cumulative radiation dose to the risk of second malignancies were evaluated. RESULTS After a median follow-up duration of 9.5 years (range, 3.0 to 30), 16 patients have developed second malignancies, which included 10 sarcomas (five osteosarcomas, three fibrosarcomas, and two malignant fibrous histiocytomas) and six other malignancies (acute myeloblastic leukemia, acute lymphoblastic leukemia, meningioma, bronchioalveolar carcinoma, basal cell carcinoma, and carcinoma-in-situ of the cervix). The median latency to the diagnosis of the second malignancy was 7.6 years (range, 3.5 to 25.7). The estimated cumulative incidence rates at 20 years for any second malignancy and for secondary sarcoma were 9.2% (SD = 2.7%) and 6.5% (SD = 2.4%), respectively. The cumulative incidence rate of secondary sarcoma was radiation dose-dependent (P = .002). No secondary sarcomas developed among patients who had received less than 48 Gy, while the absolute risk of secondary sarcoma was 130 cases per 10,000 person-years of observation among patients who had received > or = 60 Gy. CONCLUSION The overall risk of second malignancies after Ewing's sarcomas is similar to that associated with treatment for other childhood cancers. The radiation dose-dependency of secondary sarcomas justifies modification in therapy to reduce radiation doses.

Cancer survival among children and adolescents has improved markedly due to evolution of multimodal treatment that incorporates combination chemotherapy, radiation therapy and/or surgery. However, 20-30% of children with malignancies will succumb to their disease or complications associated with their disease or treatment. A major limiting factor to improvement in survival among these patients is the occurrence of intrinsic and/or acquired resistance to our treatment interventions, chemotherapy and radiotherapy. Among these mechanisms, multidrug resistance, the focus of this review, is a well-documented phenomenon whose biochemistry, pharmacology and molecular biology has been extensively studied. A role for multidrug resistance in chemoresistance and therapeutic failure in childhood malignancies is suggested by the observation of clinical resistance to treatment regimes containing agents that are known substrates of multidrug resistance mechanisms. With the current results from studies in rhabdomyosarcoma, neuroblastoma, osteosarcoma, Ewing's sarcoma, leukemia and retinoblastoma, the role of multidrug resistance is still unclear. Earlier studies attempted to define a role for P-glycoprotein-mediated multidrug resistance; however, a limited number of reports suggest that the multidrug-associated resistance protein may play an active role in neuroblastoma. Further studies will be necessary using standardized and uniform approaches for the analyses of these mechanisms. Clinical trials directed toward reversal of multidrug resistance are premature since the exact role of P-glycoprotein is controversial in pediatric malignancies, the role of other mechanisms of multidrug resistance must be assessed and selective inhibitors of multidrug resistance have yet to be developed.

✓ Little is known about low-grade astrocytoma with neuraxis dissemination at diagnosis. A review of medical records identified this phenomenon in eight of 150 pediatric patients evaluated between 1985 and 1994 for histologically confirmed low-grade astrocytoma. These patients (five male and three female) ranged in age from 5 months to 20 years (median 8 years). Symptoms of neuraxis disease were minimal or absent. Primary tumor sites were the hypothalamus in four cases, brainstem/spinal cord in three, and temporal lobe in one. Patterns of dissemination (evaluated by computerized tomography and/or magnetic resonance imaging techniques) appeared to be related to the primary site: hypothalamic tumors metastasized along the ventricular cerebrospinal fluid pathways, and tumors in other locations disseminated along subarachnoid pathways. Following initial treatment with chemotherapy (in three), partial resection (in one), radiation therapy (in three), and chemotherapy plus irradiation (in one), four patients required salvage therapy for progressive or recurrent disease. Seven of the eight patients are alive with stable or progressive disease 6 to 105 months postdiagnosis (median 15 months). Low-grade astrocytoma with initial neuraxis dissemination is responsive to chemotherapy and radiation, a proportion showing periods of stable disease. The optimum therapy or combination of therapies remains unclear.

Malignant pediatric tumors of the central nervous system (CNS) have a poor prognosis, with local failure rates as high as 50%. In an attempt to improve local tumor control, we used stereotactic interstitial therapy with 125I implants in patients with recurrent/secondary or newly diagnosed CNS malignancies. Catheters were placed using computed tomography (CT) guidance; computerized dosimetry was completed with the aid of orthogonal films. Implants delivered 1,000 cGy/day to the tumor periphery (0.5 cm beyond the boundary of enhancement on CT scans), to a total dose of 60 Gy. Hyperfractionated external beam irradiation (HEBI), started 2-4 weeks after removal of implants, delivered total doses of 66-70.4 Gy in 110-cGy fractions twice daily to a 3-cm margin around the implant volume. Eight of the 11 patients with newly diagnosed tumors also received 48.4 Gy HEBI to the craniospinal axis. Tumor regression was noted at 2 months after implantation in the 4 patients treated for recurrent/secondary tumors; local progression was subsequently documented in 2 cases at 6 and 20 months after implantation, while a third patient died 6 months after implantation with no evidence of local recurrence. The remaining recurrent/secondary tumor patient has no evidence of active recurrence 15 months after implantation. Local control was maintained in 9 of the 11 patients treated for primary tumors for a median of 27 months (range 15 to 48+ months). The two local failures occurred at 5 and 7 months after implantation. Six patients are alive without evidence of progressive disease (median = 23 months after implantation). There were no severe acute toxicities, but 7 patients later developed histologically confirmed tumor necrosis. Quality of life assessment (QLA) following initial primary therapy with implantation was evaluated utilizing an established criteria and found to be excellent with only one child showing marked QLA score decrease which was related to neurosurgical intervention for radiation-induced necrosis and dysfunctional family social situation. This small series suggests that stereotactic 125I implantation followed by HEBI merits further evaluation in selected children with supratentorial malignant lesions.

Deficits in neurocognitive functioning are an important area of late effects in survivors of pediatric brain tumors; however, a quantitative analysis of the magnitude of these deficits in survivors of brain tumors of the posterior fossa has not been conducted. Despite tumor locations in the posterior regions of the brain, individual studies have documented deficits in a variety of domains, reflective of impairment in other brain regions. The current study provides a comprehensive meta-analysis of literature on neurocognitive late effects found in survivors of posterior fossa tumors. Results indicated significant deficits in both specific and broad indices of neurocognitive functioning, and the overall magnitude of effects across domains ranged from medium to large (g= −0.62 to −1.69) with a large mean overall effect size (g= −1.03). Moderator analyses indicated significantly greater effects for survivors diagnosed at a younger age and those who received radiation therapy. These findings underscore the importance of monitoring neurocognitive late effects in survivors of pediatric brain tumors of the posterior fossa, as well as the need for more consistent consideration of demographic, diagnostic, and treatment-related variables to allow for examination of factors that moderate these deficits. (JINS, 2012,19, 1–10)

PURPOSE To determine the dose-limiting toxicity and potential efficacy of topotecan in pediatric patients with refractory malignant solid tumors. PATIENTS AND METHODS In this phase I clinical trial, 27 patients received topotecan 0.75-1.9 mg/m2 by continuous intravenous infusion daily for 3 days. Fifty-three treatment courses were given to these patients. RESULTS Myelosuppression was the dose-limiting toxicity at levels of 1.3 to 1.9 mg/m2 for 3 days, requiring significant support with transfused packed RBCs and platelets. Myelosuppression was variable in severity at the 1.0-mg/m2 dosage level; thus, additional patients were treated with this dosage, followed by human recombinant granulocyte-colony stimulating factor (G-CSF). Other toxicities were not significant. One patient with neuroblastoma had a complete response that lasted for 8 months. Stable disease activity was recorded for other patients with neuroblastoma, rhabdomyosarcoma, and islet cell carcinoma. Pharmacokinetic studies showed that topotecan plasma concentrations ranged from 1.6 to 7.5 ng/mL during infusions of 1.0 mg/m2/d, and that there was a biphasic plasma distribution with a mean terminal half-life of 2.9 +2- 1.0 hours. CONCLUSION Topotecan is a promising anticancer agent that deserves phase II testing in pediatric solid tumors. We recommend that pediatric phase II topotecan trials use 1.0 mg/m2/d for 3 days as a constant intravenous infusion, followed by G-CSF for 14 days, and that these treatment courses be repeated every 21 days.

Patients with suprasellar lesions develop profound hypothalamic obesity and listlessness with no effective treatment. We added triiodothyronine (T(3)) supplementation in 3 such patients and present their response. All had previous nutritional counseling without benefit. All were treated for diabetes insipidus (DI) and hypopituitarism; serum free thyroxine (T(4)) level was normal. A 24-year-old woman (pineal tumor and astrocytoma) had weight gain (4.7 kg/yr for 3 years), cold intolerance, fatigue, dry skin, and constipation; after T(3), she lost 14 kg over 27 months and reported overall improvement. Her bone mineral density also improved. A 10.6-year-old boy (optic glioma) was gaining 6 kg/yr for 4 years; after T(3) supplement, he lost 4.3 kg over 11 months. A 12-year-old girl (mixed germ cell tumor) had weight gain (8.3 kg/yr for 3 years) and listlessness; after T(3), she lost 8.1 kg over 16 months and had improved alertness. All patients were asymptomatic despite supraphysiologic T(3) levels. We suggest that T(3) may serve as a simple and effective supplement, which can promote weight loss and improve the well being of these patients with hypothalamic obesity.

PURPOSE The prognostic value of tumor-cell DNA content (ploidy) was evaluated in children with unresectable, nonmetastic rhabdomyosarcoma of embryonal histology. PATIENTS AND METHODS Flow-cytometric techniques were used to estimate the ploidy of tumor specimens from 34 patients with embryonal rhabdomyosarcoma who were enrolled in the intergroup rhabdomyosarcoma study III (IRS III) from 1985 to 1991. Tumors were classified as diploid or hyperdiploid (DNA content, 1.1 to 1.8 times that of normal diploid cells). The influence of ploidy on clinical outcome was assessed by the Kaplan-Meier technique and Cox regression analysis with stepwise selection. RESULTS Twelve of the tumor specimens were diploid and 22 were hyperdiploid. The patient groups defined by diploid or hyperdiploid tumors had similar presenting characteristics (eg, age, tumor size, and anatomic site). Significantly more children with hyperdiploid tumors achieved a complete response than did children with diploid tumors (85% v 42%; P = .01). The probability of progression-free survival at 5 years (+/- SE) was 91% +/- 6% for the hyperdiploid group, compared with 17% +/- 11% for the diploid group (P < .001). Hyperdiploidy was also associated with a significantly higher overall survival rate at 5 years: 96% +/- 4% versus 50% +/- 14% (P = .004). Ploidy retained its prognostic significance after adjustment for tumor site in the Cox regression model. CONCLUSION Tumor-cell ploidy strongly correlates with outcome in children with nonmetastic, unresectable embryonal rhabdomyosarcoma. The two biologically distinct groups identified by this measure would benefit from further refinements in risk-directed therapy.

PURPOSE Evaluation of high-dose chemotherapy with autologous bone marrow rescue (ABMR) in pediatric malignant gliomas. PATIENTS AND METHODS Newly diagnosed (n = 11) and recurrent (n = 2) malignant glioma patients received high-dose chemotherapy within 4 weeks of surgery; three had near total and 10 had subtotal resection/biopsy. High-dose thiotepa (300 mg/m2) and cyclophosphamide (2 g/m2) daily for 3 days were followed by ABMR; response was evaluated at day 30. At day 60, patients with at least stable disease received hyperfractionated (n = 9) or conventional external-beam radiotherapy (n = 2) preceded by local radioactive iodine 125 implantation (n = 2) or radiosurgery (n = 1). RESULTS Grade III and IV toxicities after ABMR consisted of mucositis (n = 12), cardiomyopathy (n = 1), acute abdomen (n = 1), pneumonitis (n = 2), and infection (n = 2). One complete and three partial responses were observed; the objective response rate was 31% (95% confidence interval, 9% to 61%). Seven had stable disease, one had disease progression, and one died of toxicity before response evaluation. The median overall and progression-free survival durations after combined modality therapy were 14 months (range, 4 to 30+) and 9 months (range, 0 to 30+), respectively. One patient remains progression-free at 30+ months. Radionecrosis and white matter changes occurred in three patients: one after hyperfractionated irradiation, and two after 125I implants. CONCLUSION For patients with bulky residual disease after surgery, survival with this aggressive chemotherapy and radiation regimen is not better than that reported for conventional treatment regimens.

Background Deficits in neurocognitive functioning are an important area of late effects in survivors of pediatric brain tumors, but a quantitative analysis of the magnitude of these deficits has yet to be conducted. Procedure The purpose of the current article is to provide a comprehensive meta-analysis of the literature on long-term neurocognitive effects found in these survivors. Results Results indicated significant deficits in both narrow and broad indices of neurocognitive functioning, and the overall magnitude of the effects across all domains ranged from small to large in magnitude (g = −0.45 to −1.43) with a large mean overall effect size of g = −0.91. Conclusions These findings underscore the importance of monitoring the neurocognitive late effects in survivors of pediatric brain tumors, and the need for more consistent consideration of demographic, diagnostic, and treatment-related variables in future research to allow for examination of factors that may moderate these deficits. Pediatr Blood Cancer. 2010;55:525–531. © 2010 Wiley-Liss, Inc.

Purpose: Vinorelbine (Navelbine) is an orally absorbable Vinca with broad antitumor activity. It differs from other Vinca in that it is structurally modified on the catharanthine nucleus and has differential actions on tubulin that render it less neurotoxic than other compounds in this class. We conducted a phase I study of vinorelbine given the activity of Vinca alkaloids in many pediatric tumors. Experimental Design: We evaluated the safety and pharmacokinetics of oral and i.v. vinorelbine administered weekly × 6 in children (age, 2-17 years) with different tumors. Patients with disease involvement in the bone marrow were eligible but were stratified and dose-escalated separately. Oral vinorelbine (week 1) was administered as liquid-filled gelatin capsules at thrice the i.v. dose. Intravenous vinorelbine doses of 24 to 37.5 mg/m2 were administered on weeks 2 to 6. Results: The dose-limiting toxicity in patients without marrow involvement was reversible neutropenia. Common nonhematologic toxicities included ≤ grade 2 nausea/vomiting and increased hepatic transaminases. A higher mean i.v. ClTB was observed (1.75 ± 1.0 L/h/kg) compared with adult reports, with a mean t1/2B of 16.5 ± 9.7 hours. Mean oral bioavailability was 28.5 ± 22.5%. The apparent oral clearance (12.1 ± 13.0 L/h/kg) and volume of distribution (69.4 ± 30.6 L/kg) were substantially higher than in adults given similar oral doses. Conclusions: The maximum tolerated dose in children without bone marrow involvement was 30 mg/m2, similar to that reported in adults, with myelosuppression being the dose-limiting toxicity. Higher plasma clearance resulted in lower area under the plasma concentration-time curves at a given dose compared with that reported in adults.

Hepatosplenic gammadelta T-cell lymphoma is an uncommon pediatric disease and is associated with an aggressive and often fatal course. The authors describe the case of an 8-year-old girl who presented with transaminitis and hepatosplenomegaly. Liver biopsy and peripheral blood flow cytometry were diagnostic of hepatosplenic gammadelta T-cell lymphoma. She was treated with multi-agent chemotherapy with cyclophosphamide, vincristine, prednisone, doxorubicin, and high-dose methotrexate but failed to achieve durable remission. She underwent an allogeneic bone marrow transplant from her HLA-identical brother with a preparative regimen including total body irradiation and cyclophosphamide. She is currently alive and has remained in remission for 30 months after transplantation. The authors also review the literature for similar pediatric cases.

Background In patients with neuroblastoma morphological assessment of BM for residual NB cells is not precise, particularly when the number of tumor cells is small. Procedure To develop a sensitive and rapid method of detecting NB cells in BM, we assessed the efficiency of flow cytometry (FCM) using markers CD9, CD56, and CD45. The percent of CD9+/CD56+/CD45− (NB phenotype) cells was determined by FCM in 41 samples (16 patients) at various time points. For confirmation fluorescence in situ hybridization (FISH) for 17q gain was performed. Results Nineteen of the 22 (86%) samples that were negative by morphology were positive by FCM (>0.006% CD9+/CD56+/CD45− cells). The longest time to complete the FCM study was 3 hr. In six FISH experiments the sorted CD9+/CD56+/CD45− population had a higher percentage of cells with 17q gain (11.5–95%) compared to a CD56−/CD45+ internal control population (2–8%). Conclusions Our preliminary results suggest that FCM determination of the percent of CD9+/CD56+/CD45− cells is an effective method of rapidly detecting NB cells in BM. © 2005 Wiley-Liss, Inc.

Lesions consistent with cavernous angiomas (CAs) of the brain are sometimes seen on MRI scans of the brains of patients who received radiation therapy for brain tumors as children. The lesions appear years later within brain tissue that was included in radiation fields. It is unclear whether these MRI-detected lesions are true CAs or a pathological variant. This study reports the clinical, radiographical, and pathological findings in 3 cases of radiation-induced CAs of the brain. From 1995 to 1997, 3 patients previously treated with radiation therapy (45– 55 Gy) for pediatric brain tumors (medulloblastoma, ependymoma, and a presumed midbrain astrocytoma) underwent resections of symptomatic and enlarging lesions that were consistent with a CA of the brain. All of the lesions occurred within fields of prior irradiation. None of the patients had received chemotherapy as part of their cancer treatment. CA-presenting symptoms included seizures, cranial nerve deficits, and headaches. The lesions appeared 7–19 years after radiation therapy and slowly enlarged on subsequent imaging studies. MRI scans of the lesions revealed characteristics typical of CA. The lesions became symptomatic 1–5 years after they were initially noted. Surgical resection was performed 1–2 years after symptoms began. The age at resection ranged from 15 to 23 years (10–21 years after radiation therapy). Pathological analysis of the three lesions showed typical CA characteristics. Some CAs may be caused by radiation therapy for pediatric brain tumors. They are radiologically and pathologically similar to sporadically occurring CAs of the brain and may enlarge over time and become symptomatic. CAs can be safely resected using standard microsurgical techniques.

Temozolomide is a novel second-generation oral alkylating agent with demonstrated efficacy and safety in patients with recurrent glioblastoma multiforme (GBM) and anaplastic astrocytoma (AA). A multicenter phase II trial was conducted to determine the efficacy and safety of temozolomide before radiotherapy in patients with newly diagnosed GBM and AA. Fifty-seven patients (51 adult, 6 pediatric) with newly diagnosed supratentorial GBM or AA were treated with temozolomide (200 mg/m ( 2 ) per day for 5 consecutive days every 28 days) for a maximum of 4 cycles. All patients were then treated with external beam radiotherapy. Twenty-two patients (39%) achieved objective response, including 6 (11%) with complete response (CR) and 16 (28%) with partial response (PR). Additionally, 18 (32%) patients had stable disease (SD). Of 21 patients (18 adult, 3 pediatric) with AA, 2 (10%) achieved CR, 5 (24%) achieved PR, and 8 (38%) had SD. Among adult patients with AA, the median progression-free and overall survival rates were 7.6 and 23.5 months, respectively. Among 36 patients (33 adult, 3 pediatric) with GBM, 4 (11%) had CR, 11 (31%) had PR, and 10 (28%) had SD. The median progression-free and overall survival rates among adult patients with GBM were 3.9 and 13.2 months, respectively. Temozolomide was safe and well tolerated in adult and pediatric patients. Grades 3 and 4 adverse events were reported in 16 (28%) and 7 (12%) patients, respectively. Temozolomide was safe and effective in treating newly diagnosed GBM and AA before radiotherapy. This pre-irradiation treatment approach appears promising, but will require additional evaluation in comparative studies.

Purpose: To determine the incidence of acute toxicity and treatment interruption associated with electron and photon craniospinal irradiation (CSI) in children treated with or without chemotherapy. Methods and Materials: A retrospective study involving a computerized search of the radiotherapy database at the University of Texas M. D. Anderson Cancer Center identified a total of 79 eligible patients ≤18 years old who had received electron (n = 46) or photon (n = 33) CSI from October 1980 to March 2000. Acute toxicity was graded according to the 1998 National Cancer Institute Common Toxicity Criteria. Chemotherapy sequencing was categorized as before or after CSI or no chemotherapy. The incidences of weight loss and skin toxicity were recorded and differences in treatment interruption and hematologic values with respect to modality used (electron vs. photon), age (≤6 or >6 years), and sequencing of chemotherapy were compared using chi-square tests. Results: The median age of the electron group was lower than that of the photon group (6.7 years and 11.7 years, respectively). The two groups were otherwise well matched in terms of median spinal dose (31.1 vs. 33.3 Gy), fraction size (1.57 vs. 1.63 Gy), and total treatment time (32.4 vs. 30.7 days). Only 2 patients in each group (photon and electron) had a treatment break (>3 days). The mean number of days interrupted was 0.94 (photon) and 1.1 (electron) (p = 0.72). The electron and photon groups were well balanced in terms of receiving pre-CSI chemotherapy (37% vs. 41%, p = 0.776). Chemotherapy given before radiotherapy vs. after or not at all was associated with an increased incidence of Grade 3–4 leukopenia (76% vs. 49%, p = 0.02), thrombocytopenia (90% vs. 10%, p = 0), and neutropenia (50% vs. 15%, p = 0.005). A younger age was associated with Grade 3–4 thrombocytopenia (29% vs. 8.7%, p = 0.034), and decreased hemoglobin (29% vs. 6.5%, p = 0.014). The incidence of leukocyte depression of Grade 3–4 toxicity was 62% in the electron group and 32% in the photon group (p = 0.018). The incidence of Grade 3–4 platelet toxicity was higher with electrons (21%) than with photons (4%), but the difference was of borderline significance (p = 0.053). The difference in Grade 1–2 weight loss was not statistically significant (86% electron vs. 55% photon groups, p = 0.53), and Grade 3–4 weight loss did not occur within the entire study group. Most patients experienced Grade 0–1 radiation dermatitis with either electrons or photons. Conclusion: A younger patient age (≤6 years) and the sequence of chemotherapy before radiotherapy were associated with increased acute hematologic toxicity. Grade 3–4 weight loss, a surrogate for gastrointestinal toxicity, was not observed within the entire population. Despite the increased acute hematologic toxicities associated with CSI in very young children, the vast majority of patients were able to complete photon or electron CSI with minimal to no treatment interruptions. CSI with the electron technique can be used as an alternative to photon CSI in young children, and in our experience does not require the routine use of hematopoietic growth factors.

Medulloblastoma is a rare adult primary brain tumor for which limited retrospective studies are available to elucidate natural history or to guide therapy. A retrospective chart and imaging review of adult patients (aged >18 years) with medulloblastoma was performed to identify survival and prognostic factors. Fifty-seven patients were evaluated at the University of Texas M.D. Anderson Cancer Center from 1978-1998. Statistical analysis of prognostic factors and overall survival was performed for a subgroup of 28 patients who were followed exclusively at our institution from the time of diagnosis until death or last follow-up. These 28 patients had an overall survival of 91% at 3 years and 84% at 5 years, whereas median survival was not reached after a median follow-up of 168 weeks (range, 9-602 weeks). Progression-free survival for all patients was 68% at 3 years and 62% at 5 years, and was not statistically different between poor- and standard-risk patients. Univariate analysis of clinical features, such as age, sex, extent of local disease, extent of resection, and use of adjuvant chemotherapy, did not identify any prognostic variables for survival among the 28 patients. Patterns of recurrence revealed that the posterior fossa was the most common site (56%), followed by bone marrow (25%). Adult medulloblastoma appears to have a favorable prognosis after treatment with maximally surgically feasible resection followed by craniospinal irradiation. Optimal treatment remains to be clarified, as both standard-risk and poor-risk patients have prolonged disease-free survival. The marked difference between survival and progression-free survival suggests that salvage therapy, usually with combination chemotherapy in this cohort of patients, is of benefit. More formal analysis of the survival benefit was not possible, however, because of the small number of patients treated at recurrence with any one therapeutic regimen.

The purpose of this study was to describe the cerebrospinal fluid (CSF) penetration of topotecan in humans, to generate a pharmacokinetic model to simultaneously describe topotecan lactone and total concentrations in the plasma and CSF, and to characterize the CSF and plasma pharmacokinetics of topotecan administered as a continuous infusion (CI). Plasma and CSF samples were collected from 17 patients receiving 5.5 or 7.5 mg/m2 per day as a 24-h CI (5 patients, 7 courses), or 0.5 to 1.25 mg/m2 per day as a 72-h CI (12 patients, 12 courses). CSF samples were obtained from either a ventricular reservoir (VR) or a lumbar puncture (LP). Topotecan lactone and total (lactone plus hydroxy acid) concentrations were determined by HPLC and fluorescence detection. Using MAP-Bayesian modelling, a three-compartment model was fitted simultaneously to topotecan lactone and total concentrations in the plasma and CSF. The penetration of topotecan into the CSF was determined from the ratio of the CSF to the plasma area under the concentration-time curve. The median CSF ventricular lactone concentrations, obtained prior to the end of infusion (EOI), were 0.86, 1.4, 0.73, 5.3, and 4.6 ng/ml for patients receiving 0.5, 1.0, 1.25, 5.5, and 7.5 mg/m2 per day, respectively. EOI CSF lumbar lactone concentrations measured in three patients were 0.44, 1.1, and 1.7 ng/ml for topotecan doses of 1.0, 5.5, and 7.5 mg/m2 per day, respectively. In two patients receiving 1.25 mg/m2 per day, EOI CSF concentrations were obtained simultaneously from a VR and LP; the lumbar lactone concentrations were 30% and 49% lower than the ventricular concentrations. During a 24-h and a 72-h CI, the median CSF penetration of topotecan lactone was 0.29 (range 0.10 to 0.59) and 0.42 (range 0.11 to 0.86), respectively. A three-compartment model adequately described topotecan lactone and total concentrations in the plasma and CSF. Topotecan was therefore found to significantly penetrate into the CSF in humans. The pharmacokinetic model presented may be useful in the design of clinical studies of topotecan to treat CNS tumors.

Background. Metastatic melanoma with an unidentified primary site represents 4% of all newly diagnosed cases of malignant melanoma in adults. Little is known of the incidence and clinicopathologic features of this clinical entity in the pediatric population. Methods. We reviewed all previously diagnosed cases of malignant melanoma in children and adolescents (

9547 Background: Irinotecan has shown antitumor activity in a number of pediatric tumors. In adults with colorectal cancer, combining irinotecan with cetuximab enhances clinical activity as compared to treatment with irinotecan alone. We implemented this first-in- pediatrics phase I study to determine the maximum tolerated dose (MTD) and recommended Phase II dose (RP2D) of cetuximab and irinotecan in pediatric patients. Methods: 35 heavily pre-treated pts with refractory solid tumors were enrolled: brainstem glioma/astrocytoma (16), hepatoblastoma (4), neuroblastoma (2), other (13). Weekly cetuximab was escalated in 3 sequential dose levels: 75, 150 or 250mg/m2; Irinotecan was given at 16 or 20 mg/m2/day over 1 hour [daily × 5] for two weeks, every 21 days. Correlative EGFR expression (immunohistochemistry and FISH) and/or mutations, pharmacokinetics (PK) of and immune response to cetuximab were performed. Results: Pts were treated in two age cohorts (ages 1–12 yrs = Group A, and 13–18 yrs = Group B). PK analyses show linearity, with similar t1/2, clearance, and volume of distribution between groups. Irinotecan-related DLT in 2/6 pts in Group A/dose 2 necessitated dose de-escalation. Three pts experienced Grade 3 hypersensitivity infusion reaction and were discontinued. A pt with an EGFR-negative high-grade glioma (dose level 1) achieved a >70% reduction in tumor size and remains on study for 16+ months (24 cycles). A pt with ependymoma experienced a partial response (PR) and continues on cycle 12+. 9 pts received ≥4 cycles of therapy. 16 pts had a best response of stable disease or PR (mean 17 wks, range 5–66+ wks) for a clinical benefit rate of 45%. Conclusions: The combination of cetuximab and irinotecan is well-tolerated over multiple repeat cycles without cumulative toxicity in children with refractory CNS and non-CNS solid tumors. Promising preliminary anti-cancer activity was observed in a variety of pediatric solid tumors. Detailed biologic correlative and PK data will be presented. [Table: see text] No significant financial relationships to disclose.

9548 Background: Platinums have significant activity in a wide variety of pediatric tumors, and oxaliplatin exhibits synergy with 5FU and LV in adults with colorectal cancer in FOLFOX regimens. The primary objectives of this study are to determine the maximum tolerated dose (MTD) of the modified FOLFOX6 regimen in pediatric tumors. Secondary objectives include safety, PK pharmacokinetic (PK) and PET scan efficacy analyses. Methods: Pts age 2 and LV 400 mg/m2 over 2 hours on day 1 followed by a 5FU bolus of 400 mg/m2 then 2,400 mg/m2 continuous infusion over 46 hours, every 2 weeks (3 courses = 1 cycle), with integrated PK sampling in a limited dose escalation design. Standard 3+3 dose escalation, definitions of dose limiting toxicity (DLT), and dose modification for toxicity are implemented. The MTD is expanded to 15 patients to confirm and further characterize tolerability and toxicity. Results: To date, 15 very heavily pre-treated patients (7 M, 8 F) have received 25 cycles (range 1–4, median 2) of treatment at 2 dose levels. One of 8 pts at dose level 2 (oxaliplatin 100 mg/m2) developed DLT (delay in repeat treatment > 14 days due to grade 3 platelets). Treatment has been well tolerated. The most frequently reported related grade 3–4 adverse events (AEs) are reversible leukocytes (29%), neutropenia (43%), platelets (35%) and lymphopenia (21%). 31 of 90 courses (34%) have been delayed for neutropenia and thrombocytopenia. Anti-tumor activity to date includes a confirmed partial response lasting 15 weeks in a patient with osteosarcoma, and prolonged stable disease in 5 other pts with brain tumors (2), hepatoblastoma (2) and sarcoma (1). Conclusions: The modified FOLFOX6 regimen has significant but reversible myelosuppression in heavily pre-treated pediatric patients, but is tolerable and has promising activity in several tumor types. Cohort expansion continues at 100 mg/m2 of oxaliplatin. PET scan and pharmacokinetic analyses will be presented. No significant financial relationships to disclose.

8521 Background: Vinca alkaloids have broad activity against pediatric malignancies. Vinorelbine is a unique semi synthetic vinca alkaloid that has less potential of neurotoxicity. These observatio...

The legend for Fig 1 in the report entitled "Tumor-Cell DNA Content Predicts Outcome in Children and Adolescents With Clinical Group III Embryonal Rhabdomyosarcoma" by Pappo et al (J Clin Oncol 11:1901–1905, 1993) incorrectly identified parts A and B. The legend is reprinted here correctly in its entirety with the figure. Please see the PDF for Figure.

Previous results [J. F. Kuttesch, Jr. and J. A. Nelson, Cancer Chemother. Pharmac. 8 , 221 (1982)] from this laboratory indicate that mechanisms exist for renal secretion of 2′-deoxyadenosine and possibly for reabsorption of adenosine in humans and in mice. Since significant metabolism of these purine nucleosides occurs even in the presence of adenosine deaminase inhibitors, the renal handling of a compound which is not significantly metabolized by the deaminase or by kinases was studied. Unlike 2′-deoxyadenosine itself, the 2′-deoxyadenosine analog, [4- amino -7-(2′- deoxy -β- D -erythro- pentofuranosyl )- pyrrolo -(2,3d) pyrimidine ; 2′- deoxytubercidin ] , is not significantly metabolized by mammalian tissues. In mice, the renal plasma clearance of 2′-deoxytubercidin exceeded that of inulin by about 3-fold. Also, mouse kidney slices concentratively accumulated 2′-deoxytubercidin by a saturable and metabolically dependent process. The uptake by mouse kidney slices was inhibited by classical substrates for the organic cation secretory system (tetraethylammonium, choline and N 1 -methylnicotinamide) but was not markedly inhibited by classical substrates for the organic anion secretory system ( p -aminohippurate, phenol red and probenecid). Since 2′-deoxytubercidin inhibited the active, concentrative uptake of[ 14 C]tetraethylammonium but failed to inhibit the uptake of p-[ 14 C ] aminohippurate by mouse kidney slices, it is concluded that 2′-deoxytubercidin may be secreted by the organic cation system. Additional studies are required, however, to unequivocally establish the relationships between 2′-deoxytubercidin 2′-deoxyadenosine and tetraethylammonium renal secretory mechanisms.