Philip, Philip Agop

606 Background: Between 3-5% of CRC patients have BRCA1/2 pathogenic mutations. This study aims to identify associations between BRCA1 and BRCA2 mutations and clinical characteristics in CRC. Methods: A total of 6396 CRC tumor samples were tested with Next-Generation Sequencing (NGS) on a 592-gene panel, pathogenic or presumed pathogenic variants were counted as mutations (mt). Microsatellite instability (MSI) and tumor mutational burden (TMB) were tested by NGS. Statistical correlations were investigated using ANOVA, Chi-square and t-test. Results: Among tumors sampled, 53% derived from male patients and median age was 60 years. BRCA1 mt were detected in 1.1% (n = 72) of tumors, while BRCA2 in 2.8% (n = 179). BRCA1 mt were more frequent in women (W;65%) than men (M;35%) (p = 0.0019) while no relationship with sex was seen for BRCA2 mt (42% F vs. 58% M). No significant associations with age were noticed. Majority of pathogenic mt in BRCA1 (52%; n = 34) and BRCA2 (62%; n = 103) occurred in MSI-High (MSI-H) cases. MSI-H pts had more frameshift mt in both BRCA1/2 than MSS pts. MSS cases had lower rates of BRCA1 and 2 pathogenic mt (44% and 37%, respectively). Right-sided tumors were significantly associated with BRCA1 (p = 0.0056) and BRCA2 (p < 0.0001) mt in MSI-H cases only. BRCA1/2 mt were associated with higher TMB in all CRCs, including MSI-H and MSS cases (p < 0.001). POLE mt (n = 31) were associated with higher BRCA1/2 mt rates (9.6%, 55% respectively). Among MSS cases with POLE wild-type status, BRCA1 (p = 0.0269) and BRCA2 (p = 0.0151) mt were associated with high TMB and combining both BRCA1/2 mutations led to an even higher TMB (3.6%; p = 0.001). Conclusions: This is the first study to show that BRCA1/2 mutations are more frequent in MSI-H, and independently associated with higher TMB, pathogenic POLE mutations, and right-sided tumors in MSI-H CRCs. Given their relationship with TMB, the presence of BRCA1/2 mutations may be potential predictive biomarkers for checkpoint or PARP inhibitors in CRC, a finding that should be prospectively evaluated.

60 Background: DDR mutations are associated with higher neoantigen load and tumor infiltrating lymphocytes, and are a potential biomarker for immunotherapy. We investigated the association of DDR mutations in gastric (GC), esophageal (EC), and gastroesophageal junction (GEJ) cancers with MSI, PD-L1, and TMB, known predictors for immune checkpoint inhibitors. Methods: 20 DDR mutations were tested by Next-Generation Sequencing (NGS) with a 592-gene panel on a total of 1935 (709 EC; 831 GC; 355 GEJ) cancers. TMB was assessed by NGS, MSI by NGS or fragment analysis, and PD-L1 by IHC (22c3 for CPS or SP142). Results: GC had the highest DDR mutation rate compared to EC and GEJ (27% vs. 20%, p = 0.0005 and 17%, p = 0.0002, respectively). MSI-High (MSI-H) was significantly more common in the DDR mutated cohort (DDR-M) compared to non-mutated cancers (18% vs. 1%; p < 0.0001). TMB-High (≥ 10 mutations/megabase [mt/MB]) was higher in DDR-M (35% vs. 21%; p < 0.0001); in DDR-M cohort, GC had the highest TMB compared to DDR-M EC and GEJ (mean: 13.8 vs. 9.4 vs. 10 mt/MB, respectively; p < 0.0001). DDR mutations were more frequent in the PD-L1 combined positive score (CPS) ≥ 50 group than CPS 0 (42.9% vs. 24%; p = 0.037) and CPS 1-9 (42.9% vs. 20.6%; p = 0.005). ARID1A, ATRX, BRCA2, and PTEN were the most prevalent DDR mutations in MSI-H (87%, 31%, 25%, 24%, respectively); ARID1A, ATRX, BRCA2, and PTEN in TMB-High (47%, 7.7%, 6.7%, 6.8%) and ARID1A, BRCA2, RAD50, and WRN in PD-L1 high (CPS ≥ 10) (48.5% vs. 5.2% vs. 2.5% vs. 3.4%). Conclusions: MSI-H, TMB-high and high PD-L1 expression were significantly more prevalent in the DDR-M cohort compared to non-DDR-mutated cancers, most pronounced in GC. Alterations in ARID1A, ATRX, BRCA2, and PTEN were correlated with MSI-H and TMB-high while ARID1A, BRCA2, RAD50, and WRN were correlated with increased PD-L1 expression. Our findings may help identify patients for tailored immunotherapy approaches in future clinical trials.

208 Background: PEGPH20 degrades hyaluronan (HA), a major component of the stroma, increases delivery of gemcitabine and prolongs survival in preclinical models. We evaluated the activity of PEGPH20 in combination with mFFOX in mPC , unselected for tumor HA. Methods: Pertinent eligibility: untreated mPC, PS of 0-1 and adequate organ function. Standard FFOX was modified to add prophylactic growth factor support and omit bolus 5FU. Due to increased thromboembolic (TE) events with PEGPH20, an amendment instituted LMWH prophylaxis in the PEGPH20 arm only. Following a dose finding cohort of mFFOX + PEGPH20, the Phase II study randomized patients (1:1) to the combination arm or mFFOX alone (n = 138). The primary endpoint was overall survival (OS), with a null median OS of 10 mo and an alternative of 15 mo (1-sided type 1 error 0.1, 80% power). Results: PEGPH20 at 3 mcg/kg, q2 weeks was more tolerable than twice weekly dosing. The randomized phase II study began May 2015. The planned interim futility analysis when 35 deaths occurred gave a HR of 0.44 favoring the standard arm, thus the study was closed to accrual (March 2017). As of August 22, 2017 (n = 111), the estimated median OS in the mFFOX arm was 15.1 mo (95% CI 10.1-15.7) vs 7.6 mo (95% CI 4.6-9.2) in the PEGPH20 arm. Conclusions: OS in the mFFOX control arm (15.1 mo) is longest yet reported. Addition of PEGPH20 to mFFOX is not recommended for further study and appears to be detrimental (HR = 0.48). The impact of PEGPH20 on OS was unexpected and in contrast to favorable results reported for the combination of gemcitabine/nab-paclitaxel + PEGPH20 especially in the HA high cohort (Hingorani S et al. A 4008, ASCO 2017). PEGPH20 with mFFOX caused increased toxicity (mostly GI and TE events) and decreased treatment duration compared to mFFOX alone. Tumor HA content will be analyzed. Funding: NIH/NCI grants CA180888, CA180819; and in part by Halozyme Inc. Clinical trial information: 01959139. [Table: see text]

4007 Background: NRG/RTOG 0848 is a 2-step study designed to determine whether erlotinib (E) added to gemcitabine (G) (randomized Ph II) &/or adjuvant radiation with concurrent 5-FU or capecitabine following 6 months of systemic chemotherapy (Ph III), improve survival in patients (pts) with resected pancreatic head adenocarcinoma. The erlotinib results are reported here. Methods: Eligible pts include those with resected pancreatic head adenocarcinoma, pathologic stage T1-T3, N0-1, M0; PS 0-1, & CA19-9 ≤ 180 IU/L. Pts in Arms 1 & 2 received G 1 gm/m2 weekly for 3 weeks in a 28-day cycle for 6 cycles. Pts in Arm 2 also received E 100 mg/day. The primary hypothesis for the E portion was that G+E would increase overall survival (OS) compared to G alone. With a 1-sided alpha of 0.15, 200 OS events provide 80%/90% power to detect a signal for an increase in median OS from 22 to 28.8/30.6 months (mos). OS was estimated by the Kaplan-Meier method & arms compared using the log rank test. The Cox proportional hazards model was used to analyze treatment effect. Results: 336 pts were randomized from 11/17/2009 to 2/28/2014, with 163 pts evaluable for G and 159 for G+E. Median age was 63 years (39-86). Most pts had pathologic T3 disease (78%) & CA19-9 ≤ 90 (93%). There are 32 pts (20%) with grade 4 adverse events (AEs) & 2 pts (1%) with grade 5 AEs on G and 27 (17%) & 3 (2%) on G+E arm, respectively. There are fewer grade ≥ 3 GI AEs on the G arm (22%) as compared to the G+E arm (28%), and 110 (69.2%) & 93 (59.6%) pts received at least 85% of planned G dose for the G & G+E arms, respectively. 58% of E pts received at least 85% of planned E dose. The median follow-up for alive pts is 42.5 mos (min-max: < 1-75). With 203 deaths, median & 3-yr OS (95% CI) are 29.9 mos (21.7-33.4) & 39% (30, 45) for G and 28.1 mos (20.7-30.9) & 39% (31, 47) for G+E; log-rank p = 0.62. The hazard ratio (95% CI) comparing OS of G+E to G is 1.04 (0.79- 1.38). Conclusions: The addition of adjuvant E to G did not provide a signal for increased OS in pts with resected pancreatic head cancer compared to G alone. Accrual to the trial is continuing to answer the Ph III radiation question. Clinical trial information: NCT01013649.

TPS474 Background: In pts with APC, the distal common bile duct is frequently obstructed, which can lead to elevated bilirubin levels. Normalization of bilirubin by stenting can take weeks, so treatment options that could be initiated in pts with elevated bilirubin are desirable. In a phase III trial of pts with metastatic PC, nab-P + Gem demonstrated superior efficacy vs Gem alone for all endpoints, including overall survival (OS; median, 8.7 vs 6.6 months; hazard ratio, 0.72; P < 0.001). This study will be the first to analyze safety and PK profiles of nab-P + Gem in pts with APC and CH secondary to bile duct obstruction. Methods: Treatment-naive pts (≈ 12 to 40) with APC, Karnofsky performance status ≥ 70, and CH due to bile duct obstruction are eligible. Pts with a biliary stent must have 2 stable (within 20% of each other) bilirubin readings within 48 to 72 hours of each other taken between 5 and 21 days after stenting. Exclusion criteria consist of brain metastases, any other active malignancy, infection requiring systemic therapy, a history of myocardial infarction, or current use of medications known to be strong inducers of CYP3A4 and CYP2C8. Pts will enter 1 of 2 cohorts based on bilirubin level: cohort 1, > 1.5 to 3 × upper limit of normal (ULN), or cohort 2, > 3 to 5 × ULN. Cohort 2 will proceed only after review of safety and PK data from cohort 1 by a safety monitoring committee (SMC) and a decision has been made to proceed. The starting doses are nab-P 100 mg/m2 and Gem 800 mg/m2 for cohort 1 and nab-P 75 mg/m2 and Gem 600 mg/m2 for cohort 2. Treatment will be administered on days 1, 8, and 15 of each 28-day cycle. Doses in each cohort will be modified according to tolerability as determined by the SMC. The primary endpoints are determination of maximum tolerated dose for each cohort and PK profile. Secondary endpoints include investigator-assessed objective response rate, progression-free survival, OS, PK profile of Gem, and safety. The exploratory endpoint is change in serum CA19-9 level from baseline. Enrollment is ongoing. ClinicalTrials.gov: NCT02267707. Clinical trial information: NCT02267707.

735 Background: In the phase III CORRECT study, regorafenib significantly improved overall survival and progression-free survival (PFS) vs placebo in patients with treatment-refractory mCRC. CONSIGN (NCT01538680) was a large phase IIIb study that included 2872 patients from 25 countries; it was designed to provide continued access to regorafenib for patients with mCRC who failed standard therapy and to further characterize the safety of regorafenib. In CONSIGN, adverse events (AEs) and PFS were consistent with those reported in phase III studies. We present a retrospective subgroup analysis of patients enrolled in CONSIGN in the USA. Methods: Patients with mCRC who progressed on standard therapies and had an ECOG PS 0─1 received regorafenib 160 mg QD for the first 3 weeks of each 4-week cycle. Treatment was continued until disease progression, death, or unacceptable toxicity. The primary endpoint was safety. PFS (per investigator) was the only efficacy variable assessed. Results: A total of 364 patients in the USA were assigned to treatment (all evaluable for safety). The median age was 60 years; 38% and 62% had ECOG PS 0 and 1, respectively. KRAS mutation was present in 59%, KRAS wt in 38%; 74% had ≥ 3 prior regimens for metastatic disease. Median duration of treatment was 2.3 months (range: 0–30). Median PFS (95% CI) was 2.3 (2.0–2.6) months (2.1 months KRAS wt; 2.3 months KRAS mutant). NCI-CTCAE v4.0 grade ≥ 3 AEs occurred in 81% of patients and were considered drug-related in 53% (Table). Grade ≥ 3 hepatobiliary disorders occurred in 2%. Grade ≥ 3 treatment-emergent laboratory toxicities included bilirubin (9%), AST (6%), and ALT (3%). Conclusions: In patients from the USA enrolled in CONSIGN, the safety profile of regorafenib was consistent with that of the overall population and the known safety profile of regorafenib in mCRC. Median PFS was in the range of that reported in phase III trials. Clinical trial information: NCT01538680. [Table: see text]