Outcomes of Stereotactic vs Conventional Radiation Therapy in Unresectable Pancreatic Cancer: A Real-World Retrospective Analysis

Objectives: Unresectable pancreatic cancer (UPC) has poor outcomes, and the role of radiation therapy (RT) remains incompletely defined. This retrospective study evaluated real-world outcomes following primary tumor-directed RT in UPC and compared outcomes across different RT approaches. Materials and Methods: We retrospectively identified 176 patients who underwent local RT for UPC between August 2007 and December 2022 at a single institution. 14 patients were excluded due to repeat RT, incomplete RT, or lack of follow-up, leaving 162 patients. Patients were stratified into cohorts by RT technique: conventionally fractionated RT (CFRT; >15 fractions) (n = 22, 14%), hypofractionated RT (HypoRT; ≤15 fractions and EQD2 <40 Gy for α/β = 3) (n = 50, 31%), and stereotactic body RT (SBRT; ≤5 fractions and EQD2 ≥40 Gy for α/β = 3) (n = 27, 17%). Patients presenting with de novo metastatic disease (n = 63) were analyzed separately irrespective of RT technique. Results: Mean patient age was 68.9 years, and 43% were female. Median follow-up was 12.4 months. Median overall survival (OS) and local control were 16.5 and 16.6 months, in the SBRT cohort, vs 21.8 and 26.2 months, in the CFRT cohort. All CFRT patients received chemotherapy, whereas only approximately half of the SBRT and HypoRT patients received systemic therapy. Median OS was lower among patients who did not receive chemotherapy, at 7.0 months in the SBRT cohort and 4.9 months in the HypoRT cohort. Patients presenting with metastatic disease who underwent RT had a median OS of 5.4 months, which decreased to 2.3 months in those who did not receive chemotherapy. Conclusion: Patients with good performance status who received chemotherapy appeared most likely to benefit from primary tumor-directed RT. Metastatic patients with poor performance status and inability to receive chemotherapy had limited survival and may derive less benefit from local RT. Further studies are needed to clarify the role of SBRT and optimal treatment volumes in UPC.