Phase III trial of adjuvant immunotherapy with MOAb 17–1A following resection for stage II adenocarcinoma of the colon (CALGB 9581)

Abstract

3522 Background: MoAb 17–1A targets a cell surface antigen expressed on many adenocarcinomas and improved survival in early trials of adjuvant therapy in Stage III colon cancer. The primary clinical objective of this study was to determine whether adjuvant treatment with MoAb 17–1A improved overall (OS) and failure-free survival (FFS) in patients who have had resection of a stage II (pT3NO or pT4bNO) colon cancer. The secondary objective was to investigate a panel of prognostic biological markers for potential association with OS and FFS after adjuvant therapy in these patients. Methods: Patients were randomized to either treatment with MoAb 17–1A or observation only with stratification according to degree of differentiation, vascular or lymphatic invasion, and preoperative serum CEA. Therapy consisted of an initial 2-hour infusion of 500 mg of MoAb 17–1A (cycle 1) followed by a lower dose (100 mg) every 28 days for four doses. The study was activated 5/31/97 and closed to accrual on 5/31/02 because of the discontinuation of the drug supply. Results: The final patient accrual was 1738 of 2100 targeted, with 865 on the treatment arm and 873 on the observation arm. Study results were released by the CALGB Data and Safety Monitoring Board after futility boundaries for OS and FFS were met at the fifth planned interim analysis in July 2003. As of December 2003 there were 93 (11%) Grade 3 toxicities, 18 (2%) Grade 4 toxicities, and no deaths due to treatment. Median follow-up was 32 months on MoAB17–1A and 34 months on Observation. Two hundred eleven (211) failures and 116 deaths have been observed. These comprised 104 failures and 55 deaths on the MoAB 17–1A arm and 107 failures and 61 deaths on the observation arm. Median OS and FFS have not been reached. There were no significant differences between treatment arms (OS p=0.36; FFS p=0.49). Preliminary data on marker prevalence will be available by May 2004. Conclusion: MoAb 17–1A does not appear to prolong OS or FFS in patients with Stage II colon cancer following resection. No significant financial relationships to disclose.