Chemoradiotherapy for patients with locally advanced or unresectable extra-hepatic biliary cancer

Background: Although surgical resection is the preferred curative-intent treatment option for patients with non-metastatic, extra-hepatic biliary cancer (EBC), radiotherapy (RT) or chemoradiotherapy (CRT) may be utilized in select cases when surgical resection is not feasible. The purpose of this study is to report the efficacy and adverse events (AEs) associated with CRT for patients with locally advanced and unresectable EBC. Methods: This was a retrospective cohort study of patients with EBC, including extra-hepatic cholangiocarcinoma or gallbladder cancer, deemed inoperable who received RT between 1998 and 2018. The median RT dose was 50.4 Gy in 28 fractions and 94% received concurrent 5-fluorouracil. The Kaplan- Meier method was used to estimate overall survival (OS) and progression-free survival (PFS) from the start of RT. The cumulative incidence of local progression (LP), locoregional progression (LRP), and distant metastasis (DM) were reported with death as a competing risk. Cox proportional hazards regression models were used to assess for correlation between patient and treatment characteristics and outcomes. Results: Forty-eight patients were included for analysis. The median OS was 12.0 months [95% confidence interval (CI): 2.3-73.2 months]. The 2-, 3-, and 5-year OS were 33% (95% CI: 22-50%), 20% (95% CI: 11-36%), and 7% (95% CI: 2-20%), respectively. The 2-year PFS, LP, LRP, and DM were 21% (95% CI: 12-36%), 27% (95% CI: 17-44%), 31% (95% CI: 20-48%), and 33% (95% CI: 22-50%), respectively. On univariate analysis, biologically effective dose (BED) 59.5 Gy10 was associated with improved OS [hazard ratio (HR): 0.40, 95% CI: 0.18-0.92, P=0.03] and PFS (HR: 0.37, 95% CI: 0.16-0.84, P=0.02) and primary tumor size (per 1 cm increase) was associated with worsened PFS (HR: 1.29, 95% CI: 1.02-1.63, P=0.04). BED 59.5 Gy10 remained associated with PFS on multivariate analysis (HR: 0.34, 95% CI: 0.15-0.78, P=0.01). Treatment-related grade 3+ acute and late gastrointestinal AEs occurred in 13% and 17% of patients, respectively. Conclusions: RT is associated with 3- and 5-year survival in a subset of patients with unresectable EBC. Further exploration of the role of RT as part of a multi-modality curative treatment strategy is warranted.