Background
Retrospective dose-response analysis. 79 consecutive patients with inoperable intrahepatic cholangiocarcinoma (IHCC) treated with definitive radiotherapy (RT) from 2002 to 2014. Median tumor size 7.9 cm (range 2.2–17 cm). 89% received systemic chemotherapy before RT. RT doses ranged from 35–100 Gy (median 58.05 Gy) in 3–30 fractions; median BED 80.5 Gy. Primary question: does escalating RT dose improve outcomes for large IHCC?
Interventions and follow up
Arm A: Higher dose RT (BED >80.5 Gy) — ablative
Arm B: Lower dose RT (BED ≤80.5 Gy) — non-ablative (retrospective comparison)
Primary endpoint: Overall survival and local control (retrospective dose-response analysis)
mFollow up: 33 months for living patient
Arm B: Lower dose RT (BED ≤80.5 Gy) — non-ablative (retrospective comparison)
Primary endpoint: Overall survival and local control (retrospective dose-response analysis)
mFollow up: 33 months for living patient
Results
Median OS: 30 months from diagnosis
3-year OS (BED >80.5 Gy): 73% vs 38% lower doses, P=.017
3-year LC (BED >80.5 Gy): 78% vs 45% lower doses, P=.04
BED as continuous variable: Independently predicts LC (P=.009) and OS (P=.004)
3-year OS (BED >80.5 Gy): 73% vs 38% lower doses, P=.017
3-year LC (BED >80.5 Gy): 78% vs 45% lower doses, P=.04
BED as continuous variable: Independently predicts LC (P=.009) and OS (P=.004)
Adverse events
Main adverse events: No significant treatment-related toxicities at ablative doses despite large tumor volumes. Dose escalation was feasible with modern RT techniques including proton/photon IMRT.
Conclusions
Higher ablative doses of RT (BED >80.5 Gy) significantly improved both local control (78% vs 45%) and overall survival (3-year OS 73% vs 38%) for inoperable IHCC, with long-term survival rates comparing favorably with resection, supporting dose escalation as the goal for definitive RT in IHCC.
Key Limitations
Key Limitations: Retrospective analysis with selection bias — patients receiving higher doses may have had smaller/more favorable tumors. Lack of a prospective, randomized design; confounding by chemotherapy type, performance status, and technical factors. BED cutoff of 80.5 Gy (median) is empirical, not biologically derived. Long accrual period (2002–2014) with evolving techniques makes historical comparisons difficult. 89% received prior chemotherapy — RT alone outcomes unknown.
Clinical Context
This analysis significantly changed practice for IHCC, establishing ablative RT doses (BED >80.5 Gy, roughly 58.05 Gy in 15 fx or equivalent) as the target for definitive RT. IHCC has historically been treated with palliative/low doses because of liver tolerance concerns; this study demonstrated that modern dose-escalated RT with IMRT or protons achieves exceptional outcomes. These data supported the use of SBRT/IMRT as a bridge to resection or as definitive therapy for locally advanced unresectable IHCC.
References