Survival and Toxicity in Patients With Unresectable/Inoperable Biliary Cancers Treated with SBRT vs. Conventionally Fractionated Chemoradiation.

Purpose/objective(s) The mainstay of treatment for unresectable/inoperable biliary cancers (UIBC) is chemotherapy (CHT) and radiotherapy (RT). We report our single institution clinical efficacy and safety in patients with UIBC treated with SBRT versus conventionally fractionated radiation (CRT). Materials/methods Patients with UIBC treated with SBRT (n = 18) or CRT (n = 23) between 2006 and 2020 were identified. Additional management included neoadjuvant, adjuvant and/or concurrent CHT. Kaplan-Meier estimates of progression free survival (PFS), overall survival (OS) and locoregional control (LRC) were compared with log rank tests. Toxicities during treatment and follow up were based on the CTCAE v5.0. Acute toxicity was defined as adverse events Results Of the 41 patients analyzed 54% were male, and 20% were non-white. CRT patients were younger than SBRT (median age 64 vs 76 yrs., P 5 cm tumors in the SBRT (51%) group than CRT (22%). The median SBRT dose was 60 Gy in 5 fractions and the median dose for CRT was 50 Gy in 25 fractions. SBRT dose was dichotomized into BED10 ≥ 100 Gy and 5 cm (P = 0.097). For acute toxicity, both treatments were well tolerated overall with only 1 patient with grade 3+ toxicity. 74% of CRT patients had an acute toxicity compared to 39% of SBRT patients (P = 0.024). There was no difference in late toxicity between the two groups. There was no grade 3+ late toxicity. Conclusion In this single-institution retrospective study, there was improved PFS in UIBC treated with SBRT. There was a trend towards improved LRC in larger tumors. Dose escalation to BED10 ≥ 100 Gy in this series improved OS. SBRT was also better tolerated than CRT.