Individualized Adaptive Stereotactic Body Radiotherapy for Liver Tumors in Patients at High Risk for Liver Damage: A Phase 2 Clinical Trial.

Importance: Patients with preexisting liver dysfunction could benefit the most from personalized therapy for liver tumors to balance maximal tumor control and minimal risk of liver failure. We designed an individualized adaptive trial testing the hypothesis that adapting treatment based on change in liver function could optimize the therapeutic index for each patient.
Objective: To characterize the safety and efficacy of individualized adaptive stereotactic body radiotherapy (SRBT) for liver tumors in patients who have preexisting liver dysfunction.
Design, Setting, and Participants: From 2010 to 2014, 90 patients with intrahepatic cancer treated with prior liver-directed therapy were enrolled in this large phase 2, single-arm, clinical trial at an academic medical center. All patients had at least 1 year of potential follow-up.
Interventions: Using indocyanine green retention at 15 minutes (ICGR15) as a direct biomarker of liver function and a Bayesian adaptive model, planned SBRT was individually modified midway through the course of therapy to maintain liver function after the complete course.
Main Outcomes and Measures: The primary outcome was local control; the secondary outcome was safety and overall survival.
Results: Patients were 34 to 85 years of age, and 70% (63) were male. Ninety patients (69 [77%] with hepatocellular carcinoma, 4 [4%] with intrahepatic cholangiocarcinoma, and 17 [19%] with metastatic) received treatment to 116 tumors. Sixty-two patients (69%) had cirrhosis, 21 (23%) were Child-Pugh (CP) grade B. The median tumor size was 3 cm; 16 patients (18%) had portal vein involvement. Sixty-two (69%) received all 5 fractions (47 full dose, 15 dose-reduced owing to rising ICGR15). Treatment was well tolerated, with a lower than expected complication rate without adaptation: 6 (7%) experienced a 2-point decline in CP 6 months post-SBRT. The 1- and 2-year local control rates were 99% (95% CI, 97%-100%) and 95% (95% CI, 91%-99%), respectively.
Conclusions and Relevance: We demonstrated that the treatment strategy of individualized adaptive therapy based on a direct biomarker of liver function can be used to achieve both high rates of local control and a high degree of safety without sacrificing either. Individualized adaptive radiotherapy may represent a new treatment paradigm in which dose is based on individual, rather than population-based, tolerance to treatment.
Trial Registration: clinicaltrials.gov Identifier: NCT01522937.