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

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Abstract

Purpose:

To 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 Methods:

A 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.

Results:

The 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).

Conclusions:

Using 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.

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