Recurrence, survival, and therapy-free interval after irreversible electroporation for pancreatic adenocarcinoma

Abstract

Presenter: Wooil Kwon MD, PhD | Columbia University Background: Locally advanced pancreatic cancer (LAPC) is particularly challenging to treat. Systemic therapy may prolong survival but cannot offer a cure. Patients do not qualify for resection according to international guidelines, but accumulating experience from high volume centers in the modern era of chemotherapy suggest survival benefit in select patients undergoing resection. Recent efforts have focused on expanding surgical options. Irreversible electroporation (IRE) can be used to primarily control tumors in situ or to extend resection margins. This study provides valuable insight on survival, recurrence, and complications from a center that has integrated IRE into its treatment protocols. Methods: Data were collected for patients with T4 pancreatic ductal adenocarcinoma treated with IRE at a single tertiary center from 2012-2020. Those undergoing second IRE or IRE for other diagnoses were excluded. Primary end points included patterns of adjuvant and palliative therapy, overall survival (OS), recurrence free survival (RFS) and Clavien-Dindo complications. Therapy-free interval was defined as time from last neoadjuvant chemotherapy or radiation to the initiation of adjuvant or palliative therapy for recurrence. OS and RFS were evaluated by Kaplan Meier analysis and compared via log-rank test. Potential predictive factors were evaluated by Cox proportional hazard regression. Results: Of 110 patients, 46 underwent in situ IRE and 64 for margin extension. Eight (7.27%) were treated for recurrent pancreatic adenocarcinoma. Patients were similar in baseline characteristics, tumor location, and receipt of neoadjuvant chemotherapy. Median overall tumor size of 3.4 (2.8-4.0) on preoperative imaging was not different between IRE approach (p= 0.2810), Median OS from diagnosis (28.18 months, IQR 15.94-51.91) was similar for in situ vs. resection with margin extension (30.03 vs. 24.59 months, p=0.3298). There was no difference in local/distant RFS (respectively 7.26 vs. 10.59 months, p=0.7543). Both groups were similar with regard to Grades 3-5 90-day complications (28.3% vs. 25.0%, p=0.7018). Univariate Cox regression found no individual predictors of survival or recurrence to be significant. Adjuvant chemotherapy was given to 25.53% of patients who survived beyond 90 days. Thirty-two (34.04%) were not initially treated with adjuvant therapy, but later received treatment for recurrence. This group benefitted from a median therapy-free interval of 12.08 months (9.14-27.59) from last neoadjuvant chemotherapy or radiation, while maintaining similar overall survival (21.09 months vs. 20.96 months for planned adjuvant therapy, p=0.454). Conclusion: Many patients in this series would not have been candidates for traditional surgical resection. Compared to historical controls and studies of systemic therapy alone, this study demonstrates the favorable survival outcomes of IRE. By demonstrating a median one year treatment-free interval from neoadjuvant chemotherapy or radiation, this study highlights the potential for IRE to improve quality of life by limiting the inconveniences and toxicities of systemic therapy and raises questions about the role of adjuvant therapy after maximal neoadjuvant therapy for these selected patients.