Blue, Kirsten

e16266 Background: Pancreatic cancer is one of the deadliest malignancies, with a 5 year OS of around 3%. Up to 3% of unselected patients (pts) with (PDAC) have the BRCA 1/2 mutation, while up to 15% possess HRD (ARID1A, ATM, BAP1, BARD1, BRIP1, CHEK1/2, FANCA, PALB2, RAD50, RAD51). PARP inhibitors, like olaparib, demonstrate clinical benefit in metastatic PDAC with BRCA mutations (mBRCA) and may have a role in those with HRD. The objective of this study is to determine the role of PARP inhibition in PDAC with HRD. Methods: This was a retrospective chart review of metastatic PDAC pts with germline (g) or somatic (s) mBRCA or HRD who received olaparib. An analysis of PFS and OS was performed for PDAC pts with mBRCA vs. HRD. Results: Forty-six pts with metastatic pancreatic cancer were identified to have mBRCA (n = 13) or HRD (n = 23) and received olaparib in our database. Median age was 73 years for mBRCA and 66 years for HRD. Five pts received olaparib as maintenance therapy after disease control with platinum: 2 mBRCA and 3 HRD pts. Six pts with mBRCA and 7 pts with HRD were platinum naïve prior to olaparib. Zero pts with mBRCA and 3 pts with HRD received olaparib after disease progression on platinum. The median (med)PFS for mBRCA vs. HRD was 6.1 months vs. 2.8 months (HR 0.5, 95% CI: 0.2-1.1, p = 0.07). The medOS for mBRCA vs. HRD was 7.7 vs. 5.3 months (HR 0.7, 95% CI: 0.2-1.9, p = 0.4). Of those with mBRCA who received olaparib, prior cisplatin exposure (n = 8) vs. cisplatin naïve (n = 5) led to medPFS of 6.1 vs. 7.8 months (HR 1.8, 95% CI 0.5-6.7, p = 0.3) and medOS of 6.8 months vs. 9.5 months (HR 1.5, 95% 0.3-6.4, p = 0.6). Six pts with HRD including gCHEK2 c.407T > C, gCHEK2 c.1461+1 G > A, gPALB2 gain (exon 11), sFANCI p.N1252S, sATM p.V2716A, sARID1A Q944fs*14 were noted to have disease control of at least 3 months on olaparib. Only one of these pts received olaparib as maintenance therapy after platinum. The medPFS was 6.1 months and medOS was not reached. One pt with HRD (sFANCI N1252S) had progressive disease on platinum prior to olaparib, but had stable disease > 5 months with olaparib. Conclusions: Our study suggests olaparib may have anticancer activity in PDAC with certain HRD. In addition, olaparib may have a role outside maintenance therapy in PDAC with mBRCA. Prospective studies are needed to confirm these findings.

415 Background: Immune checkpoint inhibitors (ICI) have been approved in solid tumors with dMMR. However, only limited data are available for PDAC with dMMR given the rarity of dMMR in PDAC. We evaluated efficacy of ICIs in PDAC with dMMR. Methods: Retrospective clinical and pathologic data were collected for patients (pts) with pancreatic adenocarcinoma from May 2017 to June 2020 at Moffitt cancer center. Results: We identified 10 pts with dMMR PDAC. The median age was 64.5 years (range: 42-86) and 4 pts were male. 4 pts had resectable disease, 3 had locally advanced and 3 had metastatic disease at initial diagnosis. MSH6 deficiency (def) was found in 2 cases, PMS2 def in 2, MLH/PMS2 def in 5, and MSH2/MSH6 in 1. 7 pts were treated with ICIs. 3 pts had locally advanced and 4 had metastatic disease when they started ICIs. 5 received Pembrolizumab (pem), 1 received ipilimumab/ nivolumab (ipi/nivo), and 1 received pem then ipi/nivo after progressive disease (PD) on pem. The median number of prior lines of chemotherapy was 1 (range 0-2). 6 pts were evaluable, and 1 had rapid disease progression after 1 dose of pem. Among 6 evaluable pts, 3 had an objective response (1: complete response and 2: partial response), and 2 had stable disease (SD). Median progression-free survival was 8.2 mo, and median overall survival was not reached with median follow-up (FU) of 6.8 mo. The median duration of response was not reached with a median FU of 22.6 mo. The pt with CR remained disease-free for up to 22 months. The pt whose treatment was switched to ipi/nivo after PD on pem achieved SD > 4mo on ipi/nivo. While on immunotherapy, one patient with ipi/nivo developed immunotherapy associated rash requiring systemic steroids, and another on pem developed hypothyroidism requiring levothyroxine. Conclusions: This series suggest ICIs can provide durable clinical efficacy in pts with dMMR PDAC.