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Background. For many tumour sites, external beam radiation therapy (EBRT) is delivered with a sequential two-phase treatment regime. Yet, there is a lack of consensus of how to add two different non-uniform dose distributions in order to evaluate the late radiation effect for normal tissue. The purpose of this novel investigation is to quantify the dose differences between non-corrected and fractionation-corrected combined non-uniform dose distributions. Material and methods. We used a model of an organ at risk (OAR) located in six different positions relative the treated volume giving 16 clinically representative two-phase treatment situations (46 Gy + 22 Gy). The linear-quadratic model was applied to correct for fractionation effects in each voxel before the doses were added. Dose differences were quantified using mean and maximum doses with corresponding fractionation-corrected doses as reference. Results. Non-corrected doses were higher than fractionation-corrected doses in all treatment situations (mean dose: p<0.001; maximum dose: p=0.003). With the OAR outside the treated volume, non-corrected doses were 3-6 Gy higher representing 10-50% of the reference dose (10-25 Gy); with the OAR included in the treated volume, 1-6 Gy higher representing 1-15% (30-60 Gy). Mean dose differences were generally larger than maximum dose differences. Conclusion. Substantial dose differences were present in all of the simulated treatment situations but more apparent when the OAR was located outside the treated volume in both phases. Our findings require verification in clinical cases but nevertheless indicate a need for fractionation-corrected doses in two-phase treatments both in the daily clinical routine as well as in the modelling of late radiation effects. Our data suggest that adjusting for fractionation effects would lead to lower tolerance doses than currently suggested, in particular for OARs with parallel tissue architecture. [ABSTRACT FROM AUTHOR]

Background: The aim of this treatment planning study was to investigate the potential advantages of intensity-modulated (IM) proton therapy (IMPT) compared with IM photon therapy (IMRT) in nasopharyngeal carcinoma (NPC). Methods: Eight NPC patients were chosen. The dose prescriptions in cobalt Gray equivalent (GyE) for gross tumor volumes of the primary tumor (GTV-T), planning target volumes of GTV-T and metastatic (PTV-TN) and elective (PTV-N) lymph node stations were 72.6 GyE, 66 GyE, and 52.8 GyE, respectively. For each patient, nine coplanar fields IMRT with step-and-shoot technique and 3D spot-scanned three coplanar fields IMPT plans were prepared. Both modalities were planned in 33 fractions to be delivered with a simultaneous integrated boost technique. All plans were prepared and optimized by using the research version of the inverse treatment planning system KonRad (DKFZ, Heidelberg). Results: Both treatment techniques were equal in terms of averaged mean dose to target volumes. IMPT plans significantly improved the tumor coverage and conformation (P < 0.05) and they reduced the averaged mean dose to several organs at risk (OARs) by a factor of 2-3. The low-to-medium dose volumes (0.33-13.2 GyE) were more than doubled by IMRT plans. Conclusion: In radiotherapy of NPC patients, three-field IMPT has greater potential than nine-field IMRT with respect to tumor coverage and reduction of the integral dose to OARs and nonspecific normal tissues. The practicality of IMPT in NPC deserves further exploration when this technique becomes available on wider clinical scale. [ABSTRACT FROM AUTHOR]

Nasopharyngeal carcinoma (NPC) is a rare disease in Sweden. For evaluation of the treatment outcomes in our NPC patients, 52 new cases that were referred to our department between 1991 and 2002 were retrospectively analysed. Tumor stage, according to the 1997 AJCC staging system, was I in five, II in ten, III in 12 and IV in 25 patients. Majority of the patients (87%) had World Health Organization type II-III tumors. Neoadjuvant chemotherapy was delivered in 33 patients. Thirty-two patients received hyperfractionated accelerated radiation therapy with a median dose of 64.6Gy (1.7Gy/fr bid). Conventional external irradiation with a median dose of 66Gy (2Gy/fr) was delivered to 18 patients. An intracavitary brachy-boost of 4.5-12Gy was delivered to 40 patients. Two patients were excluded from the analysis due to treatment refusal. For the patients with tumor stages I-IVB, the 5-year disease-free and overall survival rates were 61% and 55%, respectively. The 5-year local, regional, and distant relapse-free survival rates were 70%, 92% and 77%, respectively. The most frequent late side effects were xerostomia (98%), otitis (70%) and hearing deterioration (64%). Our data suggest that optimization of the treatment outcomes in NPC patients requires implementation of new therapeutic strategies. [ABSTRACT FROM AUTHOR]

In forthcoming multicentre studies on stereotactic body radiotherapy (SBRT) compliance with volume and dose prescriptions will be mandatory to avoid unnecessary heterogeneity bias. To evaluate compliance in a multicentre setting we used two cases from an ongoing phase II study of SBRT of T1-T2N0M0 inoperable NSCLC in a dummy run oriented on volumes and doses. Six Scandinavian centres participated. Each centre received CT-scans covering the whole lung volumes of two patients with instructions to follow the study protocol when outlining tumour and target volumes, prescribing doses and creating dose plans. Volumes and doses of the 12 dose plans were evaluated according to the study protocol. For the two patients the GTV volume range was 24 to 39&ThickSpace;cm 3 and 26 to 41&ThickSpace;cm 3 , respectively. The PTV volume range was 90 to 116&ThickSpace;cm 3 , and 112 to 155&ThickSpace;cm 3 , respectively. For all plans the margin between CTV and PTV in all directions followed in detail the protocol. The prescribed dose was for all centres 45&ThickSpace;Gy/3 fractions (isocentre dose about 66&ThickSpace;Gy). The mean GTV doses ranged from 63 to 67&ThickSpace;Gy and from 63 to 68&ThickSpace;Gy, respectively. The minimum doses for GTV were between 50–64&ThickSpace;Gy and between 55–65&ThickSpace;Gy, respectively. The dose distribution was conformed to PTV for 10 of 12 plans and 2 of 12 plans from one centre had sub-optimal dose distribution. Most of the volume and dose parameters for the participating centres showed fully acceptable compliance with the study protocol. [ABSTRACT FROM AUTHOR]