Abstract B85: Pathologic complete response following systemic chemotherapy with or without chemoradiotherapy for borderline resectable/unresectable pancreatic adenocarcinoma: Indiana University experience

Background: Median overall survival (OS) of patients with R0 resection of pancreatic adenocarcinoma is significantly better than those with unresected cancer, however only 15-20% of patients have resectable disease at time of diagnosis. Resectability may be achieved by the use of neoadjuvant treatment in a number of patients with initial borderline resectable pancreatic cancer (BRPC) or locally advanced pancreatic cancer (LAPC). There are very few reports of patients who achieve pathologic complete response (pCR) with neoadjuvant treatment and the follow up data on such patients is limited. Methods: We retrospectively searched the database of our institution for patients who were treated at Indiana University Simon Cancer Center between 2008 to 2014 and identified patients with BRPC/LAPC or metastatic pancreatic adenocarcinoma who had undergone pancreatectomy after receiving neoadjuvant treatment. Following resection, specimens were reviewed by a pancreatic carcinoma expert pathologist, and tumor regression grade scores was reported based on the grading by the College of American Pathologists. Patients who were found to have no residual viable disease were identified and their clinical and pathological features were acquired from the electronic medical records. Results: Eight patients were identified to have pCR with a minimum follow up of 16.5 months. At the time of diagnosis, 3 patients were considered to have BRPC, 3 had LAPC and 2 had metastatic disease. Patients underwent treatment with either gemcitabine-based regimen for a median of 3.5 months (range, 2-6 months) or FOLFIRINOX (5- fluorouracil, oxaliplatin, irinotecan, and leucovorin) for a median of 6 months (range, 6-8 months). Six patients also received stereotactic body radiation therapy with a median total dose of 54 Gy (range, 30-54 Gy). Two of the patients received concurrent capecitabine and 4 received weekly concurrent gemcitabine as a radiosensitizer while receiving radiation therapy. After completion of treatment, patients underwent radiographic restaging and all were found to have resectable disease. Patients with metastatic disease had complete radiographic response in their distant lesions. Five patients underwent distal pancreatectomy and 3 underwent pancreaticoduodenectomy. The tissue specimens were extensively reviewed and no residual tumor was found. Three patients were found to have pancreatic Intraepithelial Neoplasia (PanIN)1-2 and one patient was found to have PanIN3. During the follow up period 4 patients died, with a median OS of 17.6 months (range, 10.4-47.9 months). Four patients are still alive with median follow up of 19.9 months (range, 13.5-34.0); two of whom have no evidence of disease to date. Conclusion: This case series demonstrates complete pathologic remission in patients receiving neoadjuvant treatment for advanced pancreatic cancer. When compared to OS of patients with metastatic or locally advanced disease who do not achieve pCR or undergo resection, pCR seems to be associated with improved OS. The ideal treatment regimen and duration of treatment in order to achieve higher rates of pCR is yet to be investigated. Citation Format: Neda Hashemi-Sadraei, Hai Nguyen, Bert O’Neil, Michael G. House, Safi Shahda.{Authors}. Pathologic complete response following systemic chemotherapy with or without chemoradiotherapy for borderline resectable/unresectable pancreatic adenocarcinoma: Indiana University experience. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B85.