Survival and Toxicity in Patients With Unresectable or Inoperable Biliary Tract Cancers With Ablative Radiation Therapy Versus Nonablative Chemoradiation

Abstract

Purpose: Conventional chemoradiation (CCRT) is inadequately effective for the treatment of unresectable or inoperable biliary tract cancers (UIBC). Ablative radiation therapy (AR), typically defined as a biologically effective dose (BED) ≥80.5 Gy, has shown some promise in terms of local control and survival in these patients. We compare the efficacy and toxicity of AR to non-AR in UIBC patients. Methods and Materials: Patients with UIBC treated with stereotactic body radiation therapy (SBRT; n = 18) or CCRT (n = 28) between 2006 and 2021 were retrospectively analyzed. The associations of treatment, BED groups, selected characteristics with overall survival (OS), progression-free survival (PFS), and local control were estimated separately using Cox proportional hazards regression. Toxicity was scored using Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. Results: Median dose fractionation was 60 Gy in 5 fractions (median BED, 127 Gy) for SBRT and 50 Gy in 25 fractions (median BED, 64 Gy) for CCRT. The median follow-up of the entire cohort was 11.5 months. The 1-year OS rate was 62% for BED <80.5 versus 66% for BED ≥80.5 (P = .069). The 1-year PFS rate was 24% for BED <80.5 and 29% for BED ≥80.5 (P = .050). The 1-year local control rate was 20% for BED <80.5 and 41% for BED ≥80.5 (P = .097). BED as a continuous variable (P = .013), BED ≥100 Gy (P = .044), and race (white versus nonwhite) (P = .037) were associated with improved overall mortality. BED ≥80.5 Gy (P = .046), smaller tumor size (<5 cm; P = .038) and N0 disease (P <.0001) were associated with improved disease progression rates. Local control was improved in patients with N0 disease compared with N1 disease (P <.0001). Both treatments were well tolerated; there was no difference in acute and late toxicity between AR and non-AR. Conclusions: In this review, there was improved PFS with BED ≥80.5 Gy with a trend toward OS benefit. BED ≥80.5 Gy was achieved mostly through SBRT and was well tolerated. AR could be considered a more effective treatment modality than CCRT in patients with UIBC.