Stereotactic body radiotherapy in the management of oligometastatic and recurrent biliary tract cancer: single-institution analysis of outcome and toxicity

Introduction Biliary tract cancers (BTC) are rare malignancies arising from biliary system. Systemic therapy is the cornerstone for stage IV disease, with poor overall survival (OS). Evidence is lacking about safety and efficacy of local ablative treatments, such as surgery and stereotactic body radiotherapy (SBRT) in the context of metastatic BTC (mBTC). Materials and methods We retrospectively analyzed clinical outcomes for a cohort of mBTC patients treated with SBRT for oligometastatic disease. Inclusion criteria were 1-5 distant metastases; SBRT with a dose/fraction of a least 5 Gy to a biological effective dose (BED) of at least 40 Gy considering an alpha/beta of 10 Gy. Analyzed outcomes included local control (LC), distant progression-free survival (DPFS), PFS, and OS. Results 51 patients meeting the inclusion criteria. Primary tumor sites were intrahepatic cholangiocarcinoma (35%), extrahepatic cholangiocarcinoma (31%), ampullary adenocarcinoma (20%), gallbladder adenocarcinoma (14%). 21 patients were treated on liver lesions, 17 on nodal metastasis, 5 patients on lung lesions, 4 patients on recurrence along the extrahepatic bile duct. After a median follow-up of 14 months median OS was 13.7 months, 1- and 2-year OS were 58% and 41%, respectively. Node and lung as metastatic sites were associated with a longer OS (p < 0.001). Median LC was 26.8 months, and intrahepatic cholangiocarcinoma was associated with longer LC (p = 0.036). Median DPFS was 11 months, with 1- and 2-year DPFS of 48% and 27.8%, respectively. Ten patients reported grade 1-2 toxicity and 2 cases of acute G3 biliary obstruction. Conclusions Stereotactic body radiotherapy (SBRT) is feasible in the context of mBTC. OS and PFS results are promising, considering that our patients were heavily pre-treated with systemic therapy. Patients with nodal or lung relapse have better prognosis. Distant relapses remain the main pattern of failure, but treatment of all metastatic sites seems to improve DMFS.