Stereotactic Body Radiation Therapy after Chemotherapy for Unresectable Perihilar Cholangiocarcinoma: The STRONG Trial, a Phase I Safety and Feasibility Study.

Background: In unresectable pCCA, the standard of care is palliative chemotherapy. We investigated the feasibility and safety of adding stereotactic body radiation therapy (SBRT) after chemotherapy.

Methods: Patients with unresectable pCCA, stage T1-T4N0-N1M0, ECOG 0-1, having finished 6-8 cycles of cisplatin and gemcitabine without disease progression were eligible. SBRT was planned in 15 fractions of 3.0-4.5 Gy. The primary endpoints were feasibility (defined as completing SBRT as planned) and toxicity, evaluated within 3 months after SBRT (CTCAE v4.03). A conventional "3 + 3" design was used, corresponding to a sample size of 6 patients. Dose-limiting toxicity (DLT) was defined as grade ≥ 4 hepatobiliary or grade ≥ 3 gastrointestinal toxicity. The secondary endpoints, measured from the start of radiotherapy, were local control, progression-free survival, overall survival, and quality of life (QoL). ClinicalTrials.gov identifier: NCT03307538.

Results: Six patients were enrolled between November 2017 and March 2020. SBRT was delivered as planned. All patients were treated with 60Gy (15 × 4.0Gy). No SBRT-related DLT was observed. The most common grade ≥ 3 toxicity was cholangitis ( = 5). The median follow-up was 14 months. The 12-month local control rate was 80%. We observed no substantial changes in QoL.

Conclusion: In patients with unresectable pCCA with stable disease after palliative chemotherapy, adding SBRT is feasible and safe. The observed local control merits an additional evaluation of effectiveness.