Successful implementation of the randomized discontinuation trial design: An application to the study of the putative antiangiogenic agent carboxyaminoimidazole in renal cell carcinoma-CALGB 69901

Purpose: To assess the disease-stabilizing activity of carboxyaminoimidazole (CAI) in patients with metastatic renal cell cancer (RCC) using a randomized discontinuation trial (RDT) design. Patients and Methods: Recruited patients had a performance status of 0 to 2, minimal neuropathy or cerebellar dysfunction, measurable disease, and normal organ function. Treatment with 250 mg/d CAI was initiated in all patients and continued until disease progression in those with an objective response. Protocol treatment was discontinued for unacceptable toxicity or progressive disease; patients with stable disease at the 16-week evaluation point were randomly assigned in a double-blind manner to continued CAI or placebo. The primary end point was the stable disease rate in the randomized groups. Results: A total of 368 patients were accrued and received therapy. Ninety percent had a performance status of 0 or 1, 80% underwent a prior nephrectomy, and 41% had received no prior systemic therapy. Serious or life-threatening toxicity was experienced by 34%, with asthenia (15%) and neuropsychiatric difficulties (7%) being most common. At the randomization point, 51% of patients had progressed, 30% withdrew, 1% experienced a partial response, and 17% had stable disease and were randomly assigned. A Bayesian futility analysis utilizing the first 49 randomly assigned patients suggested that the probability of demonstrating a higher stable disease rate in the experimental group was less than 9% even under the most optimistic a priori assumptions, and further trial accrual was halted. Conclusion: CAI is inactive in RCC. The RDT design should be further explored for evaluating activity of putative disease stabilizing agents.