Background: We tested whether adjuvant radioimmunotherapy (RAIT) given after R0 resection of liver metastases (LM) of colorectal cancer is safe and can improve survival. Resection of LM from colorectal cancer is the standard of care in this setting, yet two thirds will eventually relapse, and adjuvant systemic chemotherapy has failed to improve survival.

Methods: Twenty-three patients who underwent R0 resection for LM of colorectal cancer received a dose of 40 to 60 mCi/m(2) (131)I-labetuzumab, a humanized monoclonal antibody against carcinoembryonic antigen. Safety (n = 23), disease-free survival, and overall survival (n = 19) were analyzed, and efficacy was then compared retrospectively with a similar contemporaneous group of control patients (n = 19) treated at the same institution during the same time period but without RAIT.

Results: At a median follow-up of 91 months (95% confidence interval [CI], 68.0 months to infinity), the median overall survival for RAIT patients was 58.0 months (95% CI, 55.0 months to infinity), versus 31.0 months (95% CI, 26.0 months to infinity) at a 51-month median follow-up for the controls (P = .032). The median disease-free survival for RAIT patients was 18.0 months (95% CI, 11.0-31.0 months), versus 12.0 months (95% CI, 6.5-27.0 months) for the controls (P = .565). Corresponding survival rates (Kaplan-Meier analyses) were estimated to be 94.7% at 1 year, 78.9% at 2 years, 68.4% at 3 years, and 42.1% at 5 years with RAIT and 94.7%, 68.4%, 36.8%, and 15.8%, respectively, for the controls. RAIT was beneficial independently of bilobar involvement, size and number of LM, or resection margins. Transient myelosuppression was the principal adverse effect.

Conclusions: This first evidence of a promising survival advantage of adjuvant RAIT after long-term follow-up of colorectal cancer patients given salvage resection of LM warrants confirmation in a prospective randomized trial.