Newman, Elliot

Abstract Background Surgical resection without visible or residual microscopic disease (R0 resection) is known as the optimal path to cure localized pancreatic cancer (PDAC). Neoadjuvant therapy (NAT) is used to improve R0 resection rates; however, the optimal regimen is unclear. We assessed the safety and efficacy of peri-operative gemcitabine/nab-paclitaxel (GEM/NAB) and pre-operative stereotactic body radiotherapy (SBRT) in patients with resectable (R-PDAC) and borderline resectable PDAC (BR-PDAC). Patients and Methods This was a prospective, multicenter single arm phase 2 study in patients with R-PDAC and BR-PDAC. Patients received three cycles of GEM/NAB prior to SBRT followed by surgery and three cycles of adjuvant GEM/NAB. Primary endpoint was R0 surgical resection rate in each cohort. Secondary endpoints included safety and overall survival (OS). Results Eighty-six patients consented and following radiologic screening, 49 were enrolled into two cohorts: R-PDAC (n = 20) and BR-PDAC (n = 29) between June 2016 and April 2021. Seventy percent of R-PDAC (14/20) and 55.2% of BR-PDAC patients (16/29) completed all NAT. Eleven R-PDAC (55.0%) and 11 BR-PDAC patients (37.9%) underwent surgical resection. Nine R-PDAC (45.0%) and 9 BR-PDAC patients (31.0%) had R0 resections. The median OS for R-PDAC and BR-PDAC patients with R0 resections was 22 months (95% CI: 17.7 months-NA) and 39 months (95%CI: 13.21 months-NA), respectively. Conclusion While the trial failed to meet one of its primary objectives as only 45% of R-PDAC patients had an R0 resection, the objective of 30% R0 resection for the BR-PDAC group was met. NAT should be part of current therapeutic strategies for BR-PDAC; however, our trial does not answer what is the best NAT for BR-PDAC. Trial Registration NCT02723331

4175 Background: Patients (pts) with pancreatic adenocarcinoma (PDAC) who are candidates for surgery are anatomically segregated into two groups: those with resectable tumors (R-PDAC), and those with borderline resectable tumors (BR-PDAC). For each group, complete surgical resection with no visible or microscopic disease left behind (R0 resection) is generally accepted as the path to cure. Neoadjuvant therapy (NAT) has been used to improve the R0 resection rate. However, the optimal role and type of NAT that will improve R0 resection rate and overall survival (OS) remains controversial. The Academic Gastrointestinal Cancer Consortium (AGICC) evaluated a perioperative strategy with combination chemotherapy and preoperative stereotactic radiation therapy (SBRT) to improve the R0 resection rate. Methods: This prospective, multicenter open label, single arm phase 2 clinical trial conducted among 5 member AGICC institutions enrolled pts with R-PDAC and BR-PDAC. Treatment included 3 cycles of gemcitabine (1000mg/m2) and nab-paclitaxel (125 mg/m2) (GEM/NAB) on days 1, 8 and 15 of a 28-day cycle prior to SBRT (33Gy: 6.6Gy daily x 5) followed by surgery and 3 cycles of adjuvant GEM/NAB. Accrual goal was 20 R-PDAC and 30 BR-PDAC pts selected by central radiology review. Primary objective was to estimate the R0 resection rate for each cohort. Secondary objectives included safety and tolerability of neoadjuvant treatment and OS. Results: Eighty-six pts signed consent and after radiologic screening, 20 R-PDAC patients and 29 BR-PDAC patients were found eligible to begin treatment. One R-PDAC and two BR-PDAC pts did not initiate therapy. 14 (70%) and 19 (66%) R-PDAC and BR-PDAC pts, respectively, completed all neoadjuvant chemotherapy.14 R-PDAC (70%) and 17 BR-PDAC (59%) pts completed SBRT. 11 R-PDAC pts (55%) and 11 (38%) BR-PDAC, underwent surgery. 8 R-PDAC pts (40%) had an R0 resection. One R-PDAC pt had a complete pathologic response (pCR). 8 BR-PDAC pts (28%) had an R0 resection. 19% (3/16) pts undergoing an R0 resection are alive (47-73+ mos). 16 pts (32%) had at least one grade ≥ 3 non-hematologic adverse event (AE); 25 patients (51%) had at least one grade ≥ 3 hematologic AE. 8 pts, 4 R-PDAC and 4 BR-PDAC were hospitalized prior to surgery. One pt (2%) died during NAT. There were no deaths due to surgery. Conclusions: R0 resection rates and survival in R-PDAC and BR-PDAC were low despite a perioperative approach of systemic therapy and SBRT. The lack of survival benefit of GEM/NAB as an adjuvant regimen, as well as SBRT pre-operatively (both shown in studies subsequent to this one) may explain the disappointing results. While an R0 resection for localized PDAC is recognized as essential, our results demonstrate that an R0 resection is not sufficient to cure the majority of PDAC pts who receive NAT with GEM/NAB + SBRT. Future NAT therapy trials should aim to markedly improve the pCR rates associated with R0 resection. Clinical trial information: NCT02723331 .