Long-term outcomes of induction chemotherapy and neoadjuvant stereotactic body radiotherapy for borderline resectable and locally advanced pancreatic adenocarcinoma.

Abstract

360 Background: Limited data is available for neoadjuvant treatment of borderline resectable (BRPC) and locally advanced (LAPC) pancreatic cancer. We update our institutional outcomes with a neoadjuvant chemotherapy and stereotactic body radiotherapy (SBRT) approach. Methods: We performed an IRB-approved analysis of all BRPC and LAPC patients treated with our departmental treatment protocol. After staging, medically fit patients underwent chemotherapy for 2-3 months, with regimen at the discretion of the treating medical oncologist (FOLFIRINOX, GTX, gem/abraxane, or gemcitabine alone). Patients then received SBRT delivered in 5 consecutive daily fractions with median radiation doses of 30 Gy to tumor and 40 Gy dose painted to tumor-vessel interfaces. This was followed by restaging imaging for possible resection. Overall survival (OS), event free survival (EFS), and locoregional control (LRC) rates were estimated and compared by Kaplan-Meier and log-rank methods. Results: We identified 159 patients, 110 BRPC and 49 LAPC, with 14.0 months median overall follow-up. The resection and margin negative (R0) rate for BRPC patients who completed neoadjuvant therapy was 50.9% and 96.4%, respectively. Estimated median OS was 14.4 months for BRPC patients and 11.3 months for LAPC patients (p=0.402). Median OS was 34.2 months for surgically resected patients vs 14.0 months for unresected patients (p<0.001). Five of 21 (23.8%) LAPC patients receiving FOLFIRINOX chemotherapy underwent R0 resection. In LAPC, FOLFIRINOX recipients underwent R0 resection more often than other chemotherapy recipients (5 of 21 vs. 0 of 28, p=0.011). There was a trend for improved survival in those resected LAPC patients (p=0.09). For those not undergoing resection, one year LRC was 78.4%. Grade ≥3 potentially radiation related toxicity rate was 6.9%. Conclusions: This data underscores the feasibility, safety, and effectiveness of neoadjuvant SBRT and chemotherapy for BRPC and LAPC. Compared with other chemotherapies, FOLFIRINOX induced greater tumor response in LAPC, permitting for R0 resection in a subset of LAPC patients and trend towards improved OS.