Precision Radiation Therapy for Hepatocellular Carcinoma: Exploring the Clinical Utility of Functional Liver Avoidance Planning.

Abstract

We assessed the utility of functional liver avoidance planning (FLAP) to meet clinical constraints and reduce dose to functioning liver tissue. Twenty patients (aged 52-83 years, 6 women) with varying degrees of cirrhosis (Child-Pugh [CP] scores A5-B9) underwent [99mTc] sulfur colloid single-photon emission computed tomography/computed tomography imaging with generation of functional liver volumes (FLV) at 30%max thresholds, and FLV were coregistered onto planning computed tomography scans. Half of the patients received prior liver-directed therapy (LDT). Volumetric modulated arc therapy-stereotactic body radiation therapy (SBRT) (5 fractions, 5 CP-A, 5 CP-B/C) conventional plans were optimized following American Society for Radiation Oncology consensus guidelines, and those that did not meet published functional liver dose constraints (FLV mean, FLV V20) were reoptimized for functional liver avoidance and scaled to the same target dose coverage. Scanning proton beam therapy (PBT) plans were similarly generated for hypofractionated regimens (15 fractions, 5 CP-A, 5 CP-B/C). We characterized the associations between clinical characteristics and the probability of FLAP reoptimization and correlations with FLV dose reduction. SBRT conventional plans for CP-A patients met all clinical and functional liver dose constraints, whereas 40% of CP-B/C SBRT plans, 40% of CP-A PBT plans, and 80% of CP-B/C PBT plans required reoptimization for FLV dose constraints. Compared with conventional plans, FLAP replans achieved a median reduction of 13% (range, 2%-30%) in FLV mean dose and 4% (range, 1%-10%) in FLV V20. Increasing likelihood of prior LDT correlated with a decrease in FLAP reoptimization frequency (Spearman R = -0.95, P = .05). This was reflected in CP-A SBRT patients requiring fewer functional liver avoidance replans (80% prior LDT, 0% FLAP replans) compared with CP-B/C PBT patients (10% prior LDT, 80% FLAP replans). We successfully investigated the clinical utility of functional tissue avoidance in different groups of patients with hepatocellular carcinoma as a planning strategy to preserve liver function and mitigate hepatoxicity.