Homologous recombination deficiency (HRD) alterations as a predictor of responsiveness to combination pancreatic cancer in advanced pancreatic ductal adenocarcinoma (PDAC).

Abstract

e16259 Background: Advanced PDAC is associated with a poor prognosis and median survivals of less than one year. FOLFIRINOX and Gemcitabine/Nab-Paclitaxel are both considered standard of care in the first line setting, though there is considerable variability among oncologists regarding sequencing of these regimens. Pre-clinical and clinical data support the use of platinum therapy in HRD+ PDAC, but little is known about how this translates into best practices regarding sequencing of treatment or clinical benefit relevant to Gemcitabine based therapies in this population. Methods: Using the cancer registry and Inova molecular tumor board database, we retrospectively reviewed all patients from January 2015 until November 2021 with unresectable PDAC who had NGS performed and stratified by the presence or absence of HRD mutation. HRD mutations included by BRCA1, BRCA2, PALB2, ATM, ATR, CHEK2, ARID1A, FANCA, FANCL. We analyzed for RR to Folfirinox/Folfox and Gemcitabine based therapies, adjusted time to progression on Folfirinox/Folfox (time from first dose of oxaliplatin based combination to first dose of gemcitabine to account for those who stopped oxaliplatin early for neuropathy or received maintenance therapy), and time on gemcitabine based therapy. Results: 142 consecutive patients with advanced PDAC were examined, including 20 with HRD variants. When excluding those who eventually received surgery and those who never received platinum therapy, we were left with 87 (74 in Control and 13 in HRD) for analysis. RR to Folfirinox/Folfox was 60% in HRD+ and 31.25% in control (p = 0.71) (Table). Mean adjusted time to progression on Folfirinox/Folfox was 320.0 days in HRD+ group and 252.9 in the control group (p = 0.57) (Table 2). The time on treatment for gemcitabine based combination therapy was 260.7 in HRD+ and 165.1 in control group. Conclusions: HRD+ patients had longer durations of treatment on both 5-FU based therapy and Gemcitabine based combinations. These data challenges the importance of first line platinum therapy in HRD+ patients, and further exploration should be considered.[Table: see text]