Limitations of Body Surface Area–Based Activity Calculation for Radioembolization of Hepatic Metastases in Colorectal Cancer

Abstract

PurposeTo calculate absorbed radiation doses in patients treated with resin microspheres prescribed by the body surface area (BSA) method and to analyze dose-response and toxicity relationships. Materials and MethodsA retrospective review was performed of 45 patients with colorectal carcinoma metastases who received single-session whole-liver resin microsphere radioembolization. Prescribed treatment activity was calculated using the BSA method. Liver volumes and whole-liver absorbed doses (DWL) were calculated. DWL was correlated with toxicity and radiographic and biochemical response. ResultsThe standard BSA-based administered activity (range, 0.85–2.58 GBq) did not correlate with DWL (mean, 50.4 Gy; range, 29.8–74.7 Gy; r = −0.037; P = .809) because liver weight was highly variable (mean, 1.89 kg; range, 0.94–3.42 kg) and strongly correlated with DWL (r = −0.724; P < .001) but was not accounted for in the BSA method. Patients with larger livers were relatively underdosed, and patients with smaller livers were relatively overdosed. Patients who received DWL > 50 Gy experienced more toxicity and adverse events (> grade 2 liver toxicity, 46% vs 17%; P < .05) but also responded better to the treatment than patients who received DWL< 50 Gy (disease control, 88% vs 24%; P < .01). ConclusionsUsing the standard BSA formula, the administered activity did not correlate with DWL. Based on this short-term follow-up after salvage therapy in patients with late stage metastatic colorectal carcinoma, dose-response and dose-toxicity relationships support using a protocol based on liver volume rather than BSA to prescribe the administered activity.