R. Engineer1, P. Pathare2, M. Bhandare3, R. Krishnatry4, S. Gudi2, V. Ostwal5, A. Ramaswamy5, and S. Shrikhande3; 1Department of Radiation Oncology, Tata Memorial Centre, Homi Bhabha National Institute, Mumbai, India, 2Tata Memorial Centre, Mumbai, India, 3Department of Surgical Oncology, Tata Memorial Centre, Homi Bhabha National Institute, Mumbai, India, 4Tata Memorial Centre, Homi Bhabha National Institute, Mumbai, India, 5Department of Medical Oncology, Tata Memorial Centre, Homi Bhabha National Institute, Mumbai, India
Purpose/Objective(s): Role of SBRT in patients who do not respond to NACT is not yet well defined. We conducted this study to evaluate the impact of SBRT in borderline resectable pancreatic cancer patients with suboptimal response to NACT. Materials/
Methods: All consecutive patients staged as BRPC at our center from 2016 to 2020 were included. All received NACT with mFOLFIRINOX or NAB-PACLITAXEL (4-6 cycles) followed by surgical assessment. Patients with radiological partial response (PR) were surgically explored, those with poor response or stable disease not amenable to R0 resection received SBRT and additional chemotherapy followed by surgical assessment. SBRT consisted of 42 -45 Gy over 5 fractions in 10 days.
Results: A total of 151 patients with BRPC were registered. During NACT, 44(29%) patients either defaulted or progressed and 107 (69.9%) patients completed at least 4 cycles of NACT and response assessment CECT scan was done. Post NACT, 36(33.6%) patients with partial response were surgically explored, 22(73%) underwent R0 and 8 (24%) had R1 resection (Group 1, n=30). Remaining 71(66.3%) patients had suboptimal response to NACT and were not feasible for R0 resection received additional SBRT and CT. Post SBRT 28(26.1%) patients were surgically explored and 17 (77%) underwent R0 resection whereas 5 (23%) had R1 resection (Group 2, n=22). Remaining 43(40%) (Group 3, n=43) patients continued to receive palliative chemotherapy. At median follow up of 18 months, Median overall survival (OS) and 2-year OS for the whole group (107 patients) was 18 (13-22) months and 37.1% respectively. Group 1 (Patients undergoing curative resection after NACT) had median OS of 26 (19-32) months and 2-year OS of 56 % while Group 2 (patients with addition of SBRT after NACT to achieve curative resection) had median OS of 21 (13-28) months and 2-year OS was 40.9 %. (p value=0.572). Median OS for the patients in non-resected group (Group 3, n=43) was 13 months and 2-year OS was 25.6%. There was no significant difference in DFS of the R0 resection patients in Group 1vs 2. (p value=0.250). Median OS and 2-year OS of the patients who had R0 resection was significantly better than the patients who had R1 resection (27 vs 18 months, 55.9% versus 30.8% respectively, p value=0.046). There was no difference in surgical complications or postoperative mortality between the two groups. Only 1 patient had grade 2 and 1 patient had grade 3 RT related late GI toxicity. 7 (23%) in Group 1 and 8 (36%) patients had Surgical morbidity. Conclusion: Patients diagnosed with BRPC with suboptimal response to NACT precluding resection, benefit from addition of SBRT by increasing the resectability rate and outcomes similar to the patients having partial or good response to NACT alone. SBRT does not lead to additional surgical or RT related late toxicity.
