Abagovomab as maintenance therapy in patients with epithelial ovarian cancer: a phase III trial of the AGO OVAR, COGI, GINECO, and GEICO--the MIMOSA study

Purpose To determine whether abagovomab maintenance therapy prolongs recurrence-free (RFS) and overall survival (OS) in patients with ovarian cancer in first clinical remission. Patients and Methods Patients with International Federation of Gynecology and Obstetrics stage III to IV ovarian cancer in complete clinical remission after primary surgery and platinum- and taxane-based chemotherapy were randomly assigned at a ratio of 2:1 in a phase III, double-blind, placebo-controlled, multicenter study. Abagovomab 2 mg or placebo was administered as 1-mL suspension once every 2 weeks for 6 weeks (induction phase) and then once every 4 weeks (maintenance phase) until recurrence or up to 21 months after random assignment of the last patient. The primary end point was RFS; secondary end points were OS and immunologic response. Results Characteristics of the 888 patients included: mean age, 56.3 years; Eastern Cooperative Oncology Group performance status, ≤ 1 in > 99% of patients; serous papillary subtype, 81.5%; stage III, 85.9%; and cancer antigen 125 ≤ 35U/mL after third cycle, 80.9%. Mean exposure to study treatment (± standard deviation) was 449.7 ± 333.08 days. Hazard ratio (HR) of RFS for the treatment group using tumor size categorization (≤ 1 cm, > 1 cm) was 1.099 (95% CI, 0.919 to 1.315; P = .301). HR of OS using tumor size categorization (≤ 1 cm, > 1 cm) was 1.150 (95% CI, 0.872 to 1.518; P = .322). The most frequently reported type of adverse event was an injection site reaction in 445 patients (50.2%), followed by injection site erythema and fatigue in 227 (25.6%) and 212 patients (23.9%), respectively. By the final visit, median anti–anti-idiotypic antibody level was 493,000.0 ng/mL, indicating a robust response. Conclusion Abagovomab administered as repeated monthly injections is safe and induces a measurable immune response. Administration as maintenance therapy for patients with ovarian cancer in first remission does not prolong RFS or OS.