Progression-free and overall survival in patients with relapsed/refractory germ cell tumors treated with single-agent chemotherapy: endpoints for clinical trial design.

Background: Refractory germ cell tumor (GCT) patients have a poor prognosis and limited treatment options. The identification of novel active agents may be impaired by use of response as the primary endpoint in phase 2 trials. Improved endpoints could enhance the development of new effective agents.

Methods: The characteristics and outcome of refractory GCT patients enrolled in 7 single-agent phase 2 trials conducted at Memorial Sloan-Kettering Cancer Center from 1990 to 2008 were reviewed. The study agents were suramin, all-transretinoic acid, topotecan, pyrazoloacridine, temozolomide, ixabepilone, and sunitinib. The major endpoints evaluated were response, progression-free survival (PFS), and overall survival (OS).

Results: Ninety patients (87 male, 3 female) were treated. The primary tumor site was testis in 65 patients, mediastinum in 17 patients, retroperitoneum in 4 patients, and other in 4 patients. Eighty-six patients had nonseminoma, and 4 patients had pure seminoma. Best responses were 1 (1%) partial response (ixabepilone), 15 (17%) stable disease, and 74 (82%) progressive disease. Median PFS and OS were 1.0 month (95% confidence interval [CI], 0.8-1.3) and 4.7 months (95% CI, 3.5-6.4), respectively. Eighty-six of the 90 patients have died. The 12- and 16-week PFS rates were 9% (95% CI, 3-15%) and 6% (95% CI, 1%-11%), respectively.

Conclusions: Patients with refractory GCT progressed rapidly to these single agents. PFS and OS may be useful endpoints for designing phase 2 trials testing novel agents in this population. Twelve-week PFS (with comparison to the 9% benchmark rate reported herein) is the recommended endpoint for phase 2 trial design and median OS (using 4.7 months as the predicted median for the control arm) is suggested for phase 3 trials.