Conventionally Fractionated vs. Hypofractionated Radiotherapy for Treatment of Unresectable Pancreatic Cancer: Local Control and Survival Outcomes in a Retrospective Single-Institutional Analysis

Abstract

Unresectable pancreatic cancer (UPC) is associated with dismal survival outcomes, with a reported median survival of 8-12 months. The role of radiotherapy (RT) and the choice of optimal fractionation remains unclear. Our objective was analyzing the outcomes associated with local radiotherapy as well as determine the best radiotherapeutic approach to treat these patients. From a database of 209 radiation plans of patients treated for pancreatic cancer in a single institution between August 2007 to August 2021, patients with UPC were selected for this REB approved retrospective study. From the 209 plans, 136 unique patients were identified who had RT for UPC. The mean age of the cohort was 67.6 years, 10% were >80 years and 37% were female. Median follow-up was 9.3 months. 54 patients had distant metastases at the time of RT and were analyzed separately. Outcomes where analyzed based on whether patients received Conventionally fractionated RT (CFRT) (defined as >15 fractions) (n = 23 (17%)), Hypofractionated RT (HypoRT) (defined as ≤15 fractions and EQD2<40Gy for α/β = 3) (n = 40 (29%)) and those treated with Stereotactic Body RT (SBRT) (defined as ≤5 fractions and EQD2≥40Gy for α/β = 3) (n = 19 (14%)). The mean overall survival (OS) and freedom from progression (FFP) in the SBRT cohort was 17.2 and 7.4 months respectively, in the CFRT cohort was 22.6 and 9.9 months respectively and in the HypoRT cohort was 11.4 and 4.9 months respectively. All CFRT patients received chemotherapy. Mean OS was drastically lower in SBRT and HypoRT patients who did not receive any chemotherapy (11.9 and 3.4 months respectively). Patients with metastatic disease at presentation and receiving HypoRT had mean OS of 13.4 months. The average EQD2 for the cohorts were 45.4 Gy, 49.2 Gy and 30.3 Gy for CFRT, SBRT and HypoRT respectively. Our study demonstrates that CFRT with concurrent chemotherapy offers better therapeutic outcomes in patients with UPC compared to HypoRT. The role of dose escalated SBRT needs to be explored as an equal alternative.