Timmers, Cynthia

PURPOSE This study sought to determine the prognostic significance of the WHO-defined glioma molecular subgroups along with additional alterations, including MGMT promoter methylation and mutations in ATRX, CIC, FUBP1, TERT, and TP53, in NRG/RTOG 0424 using long-term follow-up data. METHODS Mutations were determined using an Ion Torrent sequencing panel. 1p/19q co-deletion and MGMT promoter methylation were determined by Affymetrix OncoScan and Illumina 450K arrays. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method and tested using the log-rank test. Hazard ratios were calculated using the Cox proportional hazard model. Multivariable analyses (MVAs) included patient pretreatment characteristics. RESULTS We obtained complete molecular data to categorize 80/129 eligible patients within the WHO subgroups. Of these, 26 (32.5%) were IDHmutant/co-deleted, 28 (35%) were IDHmutant/non-co-deleted, and 26 (32.5%) were IDHwild-type. Upon single-marker MVA, both IDHmutant subgroups were associated with significantly better OS and PFS ( P values < .001), compared with the IDHwild-type subgroup. MGMT promoter methylation was obtained on 76 patients, where 58 (76%) were methylated and 18 (24%) were unmethylated. Single-marker MVAs demonstrated that MGMT promoter methylation was statistically significant for OS ( P value < .001) and PFS ( P value = .003). In a multimarker MVA, one WHO subgroup comparison ( IDHmutant/co-deleted v IDHwild-type) was significant for OS ( P value = .045), whereas MGMT methylation did not retain significance. CONCLUSION This study reports the long-term prognostic effect of the WHO molecular subgroups, MGMT promoter methylation, and other mutations in NRG/RTOG 0424. These results demonstrate that the WHO molecular classification and MGMT both serve as strong prognostic indicators, but that MGMT does not appear to add statistically significant prognostic value to the WHO subgrouping, above and beyond IDH and 1p/19q status.

PURPOSENRG Oncology/RTOG 9802 (ClinicalTrials.gov Identifier: NCT00003375 ) is a practice-changing study for patients with WHO low-grade glioma (LGG, grade II), as it was the first to demonstrate a survival benefit of adjuvant chemoradiotherapy over radiotherapy. This post hoc study sought to determine the prognostic and predictive impact of the WHO-defined molecular subgroups and corresponding molecular alterations within NRG Oncology/RTOG 9802.METHODSIDH1/2 mutations were determined by immunohistochemistry and/or deep sequencing. A custom Ion AmpliSeq panel was used for mutation analysis. 1p/19q codeletion and MGMT promoter methylation were determined by copy-number arrays and/or Illumina 450K array, respectively. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Hazard ratios (HRs) were calculated using the Cox proportional hazard model and tested using the log-rank test. Multivariable analyses (MVAs) were performed incorporating treatment and common prognostic factors as covariates.RESULTSOf the eligible patients successfully profiled for the WHO-defined molecular groups (n = 106/251), 26 (24%) were IDH-wild type, 43 (41%) were IDH-mutant/non-codeleted, and 37(35%) were IDH-mutant/codeleted. MVAs demonstrated that WHO subgroup was a significant predictor of PFS after adjustment for clinical variables and treatment. Notably, treatment with postradiation chemotherapy (PCV; procarbazine, lomustine (CCNU), and vincristine) was associated with longer PFS (HR, 0.32; P = .003; HR, 0.13; P < .001) and OS (HR, 0.38; P = .013; HR, 0.21; P = .029) in the IDH-mutant/non-codeleted and IDH-mutant/codeleted subgroups, respectively. In contrast, no significant difference in either PFS or OS was observed with the addition of PCV in the IDH-wild-type subgroup.CONCLUSIONThis study is the first to report the predictive value of the WHO-defined diagnostic classification in a set of uniformly treated patients with LGG in a clinical trial. Importantly, this post hoc analysis supports the notion that patients with IDH-mutant high-risk LGG regardless of codeletion status receive benefit from the addition of PCV.

Abstract Purpose: The RAS/RAF/MEK/ERK signaling pathway is critical to the development of colorectal cancers, and KRAS, NRAS, and BRAF mutations foster resistance to radiation. We performed a phase I trial to determine the safety of trametinib, a potent MEK1/2 inhibitor, with 5-fluorouracil (5-FU) chemoradiation therapy (CRT) in patients with locally advanced rectal cancer (LARC). Patients and Methods: Patients with stage II/III rectal cancer were enrolled on a phase I study with 3+3 study design, with an expansion cohort of 9 patients at the MTD. Following a 5-day trametinib lead-in, with pre- and posttreatment tumor biopsies, patients received trametinib and CRT, surgery, and adjuvant chemotherapy. Trametinib was given orally daily at 3 dose levels: 0.5 mg, 1 mg, and 2 mg. CRT consisted of infusional 5-FU 225 mg/m2/day and radiation dose of 28 daily fractions of 1.8 Gy (total 50.4 Gy). The primary endpoint was to identify the MTD and recommended phase II dose. IHC staining for phosphorylated ERK (pERK) and genomic profiling was performed on the tumor samples. Results: Patients were enrolled to all dose levels, and 18 patients were evaluable for toxicities and responses. Treatment was well tolerated, and there was one dose-limiting toxicity of diarrhea, which was attributed to CRT rather than trametinib. At the 2 mg dose level, 25% had pathologic complete response. IHC staining confirmed dose-dependent decrease in pERK with increasing trametinib doses. Conclusions: The combination of trametinib with 5-FU CRT is safe and well tolerated, and may warrant additional study in a phase II trial, perhaps in a RAS/RAF-mutant selected population.

746 Background: Pelareorep is a proprietary formulation of live, replication-competent, naturally occurring Reovirus Type 3 Dearing strain. A randomized phase II trial of pelareorep in combination with carboplatin and paclitaxel in first-line treatment of metastatic PDAC (NCT01280058) was performed. Although pelareorep did not improve the primary endpoint of progression-free survival compared to carboplatin and paclitaxel alone, impressive durable responses were seen in the pelareorep arm in some patients (pts). Further, prior studies have noted the immunomodulatory carcinoembryonic antigen-related cell adhesion molecule (CEACAM6/CD66c) as a receptor for specific viral subtypes. We thus speculated that altered CEACAM6 levels may be predictive for pelareorep sensitivity. Methods: Pre-treatment tissue biopsies were collected prior enrolment for all 73 pts on study. Evaluable pts with transcriptomic data was available for only 31 pts. RNA was purified from FFPE tissue and gene expression analysis was performed using SensationPlus FFPE Amplification and WT labelling kit and the Human Transcriptome Array 2.0. CEACAM6 protein expression was determined by immunohistochemistry. Differential gene expression and survival analysis using were performed in R/Bioconductor. Appropriate corrections for multiplicity were performed. Results: When comparing extraordinary responders in the pelareorep treated arm to those with poor outcomes, low levels of CEACAM6 mRNA expression were associated with prolonged PFS in pelareorep-treated pts (adjusted p = 0.05). This effect was not seen in non-pelareorep treated pts. The luminal, but not the cytoplasmic immunohistochemistry score, was highly correlated with mRNA expression levels of CEACAM6, p = 0.001. Modulation of CEACAM6 in vitro and in vivo are underway. Conclusions: CEACAM6 may be a candidate biomarker of sensitivity to pelareorep and, in theory, could improve viral trafficking of this compound in tumor cells. Clinical trial information: NCT01280058 . [Table: see text]

Abstract Introduction: 5-fluorouracil (5-FU)-based chemoradiation (CRT) is a standard neoadjuvant treatment strategy for the treatment of locally-advanced rectal adenocarcinomas (LARC). MEK-1/2 inhibition has been shown to radiosensitize Ras mutant tumors in preclinical models, including colorectal cancer. In this phase 1 trial, we are testing MEK-1/2 inhibition in combination with neoadjuvant CRT for LARC. Methods: This trial is a standard 3+3 design testing 3 dose levels of the MEK-1/2 inhibitor trametinib in combination with CRT: 0.5 mg, 1.0 mg, and 2.0 mg daily, followed by an expansion cohort. All patients first receive a one week lead-in dosing of trametinib monotherapy, and undergo a tumor biopsy at the end of that week to assess pharmacodynamic inhibition by immunohistochemistry (IHC). Then, patients receive standard CRT (5-FU 225 mg/m2 per day by continuous infusion during radiotherapy, and 50.4 Gy in 28 fractions, 5 days/ week) in combination with trametinib (5 days/week). Patients have total mesorectal excision (TME) 6-10 weeks after completion of CRT. Results: 17 patients have been enrolled to date, with current enrollment occurring on the trametinib 2 mg expansion cohort (total 18 patients planned). Of these, 15 patients (10 males, 5 females) have toxicity and surgical response data available. Median age is 53 years (range 35-74 years), and 6 patients have Stage II disease, while 9 patients with Stage III disease. There have been no grade 4-5 toxicities. One dose-limiting toxicity (DLT) of diarrhea occurred in the 2mg dose cohort, attributed mainly to 5FU CRT, but led to trametinib discontinuation. Generalized skin rash led to trametinib discontinuation after 2 weeks of therapy for 1 patient and was held for 3 days for 2 patients. All patients completed TME, and 3 patients had wound infection at 2 weeks after TME, while 2 patients had perineal wound infection at 4 weeks after TME. Three out of 9 (33%) patients at the 2mg dose cohort had a pathologic complete response (pCR), and 2/9 (22%) patients had a near pCR. Adjuvant chemotherapy was given to 10 patients, 4 patients did not receive (3 refused), and 1 patient is pending. Correlative research studies have been performed in the first 12 patients enrolled. Examination of phospho-ERK levels using Vectra quantitative immunohistochemistry in pre-treatment versus post-lead-in trametinib tumor tissue reveals dose-dependent decreases in p-ERK expression in both tumor and stromal tissue as trametinib is increased from 0.5 to 2.0 mg (range 18-46% absolute reduction), with maximal reduction observed in the 2 mg cohort. Additionally, we have performed whole exome sequencing of a custom panel of 279 cancer associated genes (IGNITE platform) in tumor and normal tissue, and have identified high frequency mutations in KRAS, BRAF, and TP53, as well as additional lower frequency mutations in every tumor. One patient was noted to have microsatellite instability. Finally, we will present data correlating degree of change in p-ERK staining, mutational analysis, and mismatch repair status with pathologic response. Conclusions: The combination of trametinib with 5-FU-based CRT for LARC is feasible with promising signs of clinical activity and tolerability. Initial analysis of tumor tissue confirms dose-dependent pharmacodynamic inhibition of ERK-1/2 within 5 days of starting trametinib. Citation Format: Terence M. Williams, Christina Wu, Lai Wei, Emily Chan, Ryan Robb, Sameek Roychowdhury, Amy Webb, Cynthia Timmers, Tanios Bekaii-Saab, Evan Wuthrick. A phase I trial combining MEK-1/2 inhibition in combination with 5-fluorouracil and radiation for locally-advanced rectal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT088. doi:10.1158/1538-7445.AM2017-CT088