Jaeckle, Kurt A.

AbstractThe population pharmacokinetic model reported here was developed using data from 2 phase 2 trials of irinotecan for treatment of malignant glioma to quantify the impact of concomitant therapy with enzyme‐inducing antiepileptic drugs (EIAEDs) on irinotecan pharmacokinetics. Patients received weekly irinotecan doses of 100 to 400 mg/m2, and plasma samples were collected and analyzed for irinotecan and its APC, SN‐38, and SN‐38G metabolites. Nonlinear mixed‐effects modeling was employed for population pharmacokinetic analysis. Concomitant therapy with phenytoin, phenobarbital, or carbamazepine increased the clearances of irinotecan, SN‐38, and SN‐38G but not APC. SN‐38 clearance was 2‐fold higher with concomitant EIAED use, resulting in 40% lower SN‐38 exposure. Evaluation of additional covariates revealed no clinically relevant effects of sex or concomitant corticosteroid use. The population pharmacokinetic model suggests that a 1.7‐fold increase in irinotecan dose may compensate for decreases in SN‐38 exposure in the presence of concomitant EIAEDs. Although slightly more conservative, this dose adjustment is consistent with those recommended based on increases in the maximally tolerated dose for malignant glioma patients receiving EIAEDs and may be an appropriate starting point for further investigation when extrapolating to other cancer types or alternative regimens.

Abstract Background: Glioblastomas (GBMs) are aggressive primary brain tumors with high levels of genomic heterogeneity impacting prognosis and treatment response. A recurrent in-frame deletion within the extracellular domain of the epidermal growth factor receptor (EGFR variant III, or vIII) is found in a substantial fraction of GBMs. Methods: The Radiation Therapy Oncology Group (RTOG) 0525 trial of temozolomide dosing in newly-diagnosed GBM enrolled 1174 patients. Of these, 494 eligible GBMs were analyzed for EGFRvIII expression by RT-PCR. The Kaplan-Meier method was used to compare the progression free survival (PFS) and overall survival (OS) of GBMs expressing EGFRvIII with those not expressing EGFRvIII. Results: 142 of 494 tested GBMs (29%) had expressed EGFRvIII. There were no significant differences in PFS or OS between patients whose tumors did (494) or did not (631) undergo EGFRvIII expression analysis. EGFRvIII expression was significantly associated with age (p=0.005), Karnofsky performance status (p=0.02), and RTOG recursive partitioning analysis (RPA) class (p=0.005). EGFRvIII expression analyzed in the entire study population did not reveal an association with PFS or OS. In a univariate subgroup analysis of patients treated on the standard-of-care arm of RTOG-0525, EGFRvIII expression was was significantly associated with worse PFS (HR=1.43, 95% CI: [1.05, 1.96], p=0.025), and worse OS (HR 1.45, 95% CI:[1.03, 2.05], p=0.032). However, in multivariate models, when adjusted for RPA class and MGMT methylation status, EGFRvIII was not an independent predictor of either PFS or OS. Conclusion: For GBMs treated with standard-of-care therapy in RTOG-0525, EGFRvIII expression was associated with worse PFS and OS. However, well-established stratification metrics such as age, KPS, and RPA override this prognostic association, suggesting that trials of therapeutic modalities directed against EGFRvIII should utilize these standard prognostic variables when survival is being analyzed or compared. Project Support: This project was supported by RTOG grant U10 CA21661, and CCOP grant U10 CA37422 from the National Cancer Institute (NCI) and Schering-Plough Corporation. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A110. Citation Format: Daniel P. Cahill, Asha George, Mark R. Gilbert, Arnab Chakravarti, Roger Stupp, Monika Hegi, Paul Brown, Kurt A. Jaeckle, Benjamin Corn, Erik P. Sulman, Luis Souhami, Maria Werner-Wasik, Bethany M. Anderson, Minesh Mehta, Kenneth D. Aldape. EGFRvIII expression is associated with shorter progression-free and overall survival in glioblastoma patients treated with standard-of-care temozolomide and radiation: A report from the RTOG-0525 trial. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A110.

Purpose Radiotherapy with concomitant and adjuvant temozolomide is the standard of care for newly diagnosed glioblastoma (GBM). O 6 -methylguanine-DNA methyltransferase (MGMT) methylation status may be an important determinant of treatment response. Dose-dense (DD) temozolomide results in prolonged depletion of MGMT in blood mononuclear cells and possibly in tumor. This trial tested whether DD temozolomide improves overall survival (OS) or progression-free survival (PFS) in patients with newly diagnosed GBM. Patients and Methods This phase III trial enrolled patients older than age 18 years with a Karnofsky performance score of ≥ 60 with adequate tissue. Stratification included clinical factors and tumor MGMT methylation status. Patients were randomly assigned to standard temozolomide (arm 1) or DD temozolomide (arm 2) for 6 to 12 cycles. The primary end point was OS. Secondary analyses evaluated the impact of MGMT status. Results A total of 833 patients were randomly assigned to either arm 1 or arm 2 (1,173 registered). No statistically significant difference was observed between arms for median OS (16.6 v 14.9 months, respectively; hazard ratio [HR], 1.03; P = .63) or median PFS (5.5 v 6.7 months; HR, 0.87; P = .06). Efficacy did not differ by methylation status. MGMT methylation was associated with improved OS (21.2 v 14 months; HR, 1.74; P < .001), PFS (8.7 v 5.7 months; HR, 1.63; P < .001), and response (P = .012). There was increased grade ≥ 3 toxicity in arm 2 (34% v 53%; P < .001), mostly lymphopenia and fatigue. Conclusion This study did not demonstrate improved efficacy for DD temozolomide for newly diagnosed GBM, regardless of methylation status. However, it did confirm the prognostic significance of MGMT methylation. Feasibility of large-scale accrual, prospective tumor collection, and molecular stratification was demonstrated.

Abstract Purpose: We hypothesized that vertical blockade of VEGF signaling by combining bevacizumab with sorafenib in patients with recurrent glioblastoma would result in a synergistic therapeutic effect. We also investigated whether VEGF, VEGFR2 and hypoxia-inducible factor-1α single-nucleotide polymorphisms (SNP), circulating biomarkers of angiogenesis, and MRI markers such as apparent diffusion coefficient (ADC) are correlated with treatment efficacy and/or toxicity. Experimental Design: Patients received bevacizumab (5 mg/kg every 2 weeks) with sorafenib (200 mg twice a day, weekly, days 1–5; group A). Due to toxicity, the starting sorafenib dose was subsequently modified to 200 mg every day (group B). Results: Fifty-four patients were enrolled: 19 patients in group A and 35 in group B. Objective response rate was 18.5% with median duration of 6.7 months (range 0.5–24.1 months). Six-month progression-free survival (PFS6) was 20.4% (11/54), and median overall survival (OS) was 5.6 months [95% confidence interval (CI), 4.7–8.2]; outcome was similar between the two dose groups. We identified SNPs in the VEGF and VEGFR2 promoter regions, which were associated with PFS6 (P &lt; 0.022). Among molecular markers of angiogenesis, a higher log2 baseline level of stromal cell–derived factor-1 was associated with PFS6 success (P = 0.04). Circulating endothelial cells decreased during treatment with subsequent increase at disease progression (P = 0.022). Imaging analysis showed a trend associating ADC-L with poor outcome. Conclusions: The bevacizumab/sorafenib combination did not improve outcome of patients with recurrent glioblastoma versus historic bevacizumab-treated controls. Biologic markers of response and resistance to bevacizumab in gliomas were identified which merit prospective validation. Clin Cancer Res; 19(17); 4816–23. ©2013 AACR.

Abstract Purpose: Surrogate biomarkers are lacking for predicting or monitoring response to anti-angiogenesis therapies. We investigated whether circulating biomarkers (CBMs) of angiogenesis (i.e., bFGF, SDF-1α, HGF, sKIT, Ang-2, and PlGF) correlated with treatment efficacy in a pooled analysis of metastatic colorectal cancer (mCRC) and recurrent glioblastoma multiforme (rGBM) patients (pts) treated with bevacizumab/sorafenib (BEV/SOR). Experimental procedures: Peripheral blood samples were obtained for CBM analyses from pts enrolled in the North Central Cancer Treatment Group (NCCTG) phase II studies N054C (mCRC, n=75, Grothey, ASCO 2010) and N0776 (rGBM, n=54, Galanis, ASCO 2010). Blood collection time points were: baseline (BL), cycle 1 day 3 (C1D3), prior to treatment cycles 2, 3, 5, 7, 9, 11, 13, and after the pt went off study. Plasma CBM levels were determined by commercially-available ELISAs (R&D Systems) and performed according to manufacturer's instructions. For each CBM, a linear regression model that adjusted for study was used to evaluate the correlation with either progression-free survival (PFS) success/failure or progression within 14 days of the last blood draw for the following measures: absolute BL levels, log2 BL levels; C1D3 log2-fold change (FC) from BL, prior to cycle 2 log2-FC from BL, last draw log2-FC from BL, and last draw log2-FC from prior draw. Results summary: There appears to be no significant difference in the PFS or overall survival (OS) between the pts on these two studies; therefore, we pooled the patients from both studies for a combined analyses. We found no difference in absolute or log2 levels for any of the CBMs during the course of BEV/SOR treatment. In these pooled analyses, we found increased absolute and increased log2 BL SDF-1α levels were significantly correlated with PFS success (p=0.023 and p=0.02, respectively). After correcting for multiple comparisons (method of Benjamini & Hochberg) the p-values &lt;0.05 had a false-discovery-rate of 41.4%. None of the other CBM measures were significantly correlated with either PFS success/failure or progression within 14 days of the last blood draw (all p&gt;0.10). Conclusions: This study provides preliminary evidence that SDF-1α may be a useful CBM for determining treatment efficacy in these pts treated with BEV/SOR. Further prospective validation of SDF-1α for predicting pt progression with this treatment combination in advanced disease (e.g., mCRC and rGBM) appears warranted. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5562. doi:1538-7445.AM2012-5562