Search

Background We aimed to determine whether plasma cell-free DNA (cfDNA) concentration is associated with survival in patients with isocitrate dehydrogenase (IDH) wild-type glioblastoma (GBM). Methods Pre-operative and post-chemoradiotherapy blood samples were prospectively collected from patients with newly diagnosed IDH wild-type GBM. Patients underwent surgical resection or biopsy and received adjuvant radiotherapy with concomitant temozolomide. Cell-free DNA (cfDNA) was isolated from plasma and quantified using SYBR Green-based q polymerase chain reaction (qPCR). Results Sixty-two patients were enrolled and categorized into high vs. low cfDNA groups relative to the pre-operative median value (25.2 ng/mL, range 5.7–153.0 ng/mL). High pre-operative cfDNA concentration was associated with inferior PFS (median progression-free survival (PFS), 3.4 vs. 7.7 months; log-rank P = .004; hazard ratio [HR], 2.19; 95% CI, 1.26–3.81) and overall survival (OS) (median OS, 8.0 vs. 13.9 months; log-rank P = .01; HR, 2.43; 95% CI, 1.19–4.95). After adjusting for risk factors, including O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status, pre-operative cfDNA remained independently associated with PFS (HR, 2.70; 95% CI, 1.50–4.83; P = .001) and OS (HR, 2.65; 95% CI, 1.25–5.59; P = .01). Post-hoc analysis of change in cfDNA post-chemoradiotherapy compared to pre-surgery (n = 24) showed increasing cfDNA concentration was associated with worse PFS (median, 2.7 vs. 6.0 months; log-rank P = .003; HR, 4.92; 95% CI, 1.53–15.84) and OS (median, 3.9 vs. 19.4 months; log-rank P < .001; HR, 7.77; 95% CI, 2.17–27.76). Conclusions cfDNA concentration is a promising prognostic biomarker for patients with IDH wild-type GBM. Plasma cfDNA can be obtained noninvasively and may enable more accurate estimates of survival and effective clinical trial stratification.

Background Plasma cell-free DNA (cfDNA) concentration is lower in glioblastoma (GBM) compared to other solid tumors, which can lead to low circulating tumor DNA (ctDNA) detection. In this study, we investigated the relationship between multimodality magnetic resonance imaging (MRI) and histopathologic features with plasma cfDNA concentration and ctDNA detection in patients with treatment-naive GBM. Methods We analyzed plasma cfDNA concentration, MRI scans, and tumor histopathology from 42 adult patients with newly diagnosed GBM. Linear regression analysis was used to examine the relationship of plasma cfDNA concentration before surgery to imaging and histopathologic characteristics. In a subset of patients, imaging and histopathologic metrics were also compared between patients with and without a detected tumor somatic mutation. Results Tumor volume with elevated (>1.5 times contralateral white matter) rate transfer constant (Kep, a surrogate of blood–brain barrier [BBB] permeability) was independently associated with plasma cfDNA concentration (P = .001). Histopathologic characteristics independently associated with plasma cfDNA concentration included CD68+ macrophage density (P = .01) and size of tumor vessels (P = .01). Patients with higher (grade ≥3) perivascular CD68+ macrophage density had lower volume transfer constant (Ktrans, P = .01) compared to those with lower perivascular CD68+ macrophage density. Detection of at least 1 somatic mutation in plasma cfDNA was associated with significantly lower perivascular CD68+ macrophages (P = .01). Conclusions Metrics of BBB disruption and quantity and distribution of tumor-associated macrophages are associated with plasma cfDNA concentration and ctDNA detection in GBM patients. These findings represent an important step in understanding the factors that determine plasma cfDNA concentration and ctDNA detection.

INTRODUCTION: To improve surgical resection of brain tumors, our lab has pioneered a novel fluorescent dye technique, Second-Window Indocyanine-Green (SWIG), that relies on passive delivery and accumulation of indocyanine-green (ICG) in neoplastic tissue via the enhanced permeability and retention effect. We hypothesize that SWIG can provide early localization of brain metastasis prior to dural opening and can improve identification of surgical margins. METHODS: Subjects were prospectively enrolled in clinical trial after informed consent. Approximately 24 hours prior surgery, subjects were infused intravenously with 2.5mg/kg or 5mg/kg of ICG. Intraoperatively, a dedicated near-infrared (NIR) camera was used to detect ICG signal. After bone flap removal, the NIR imaging system was positioned above the presumed location of tumor. Additional NIR images were obtained after dural opening, corticectomy, and after conventional white-light surgical resection. RESULTS: We enrolled 50 patients with 51 total intraparenchymal brain metastases (23 lung, 7 breast, 8 GU/GI, 4 melanoma, and 7 others). Prior to dural opening, NIR signal was identified in 35 patients at an average depth of 4.3mm with SBR = 5.3 + 3.7. In the seven patients where NIR signal could not be identified prior to dural opening, tumor depth was an average of 8.4mm from cortical surface. Upon dural opening and tumor identification, all 51 tumors demonstrated strong NIR signal with SBR = 6.2 + 2.8. With white light alone, sensitivity/specificity/PPV/NPV for tumor detection was 83%, 94%, 98%, 57%. With NIR, sensitivity/specificity/PPV/NPV for tumor detection was 100%, 29%, 85%, 100%. DISCUSSION: NIR fluorophores are superior to visible light fluorophores in their depth of penetration. All contrast-enhancing brain metastasis accumulate ICG using our SWIG technique, and NIR fluorescence could be used to localize brain metastasis prior to dural opening. NIR fluorophores are likely to represent the next phase in tumor visualization given the rapid growth of fluorophores targeted to systemic cancers.