Comparative Effectiveness of Mitoxantrone Plus Prednisone Versus Prednisone Alone in Metastatic Castrate-Resistant Prostate Cancer After Docetaxel Failure

BACKGROUND: Mitoxantrone was approved for use in metastatic castrate-resistant prostate cancer (mCRPC) based on pain palliation without observed survival benefit in a small phase III trial in 1996. To re-evaluate for possible survival benefits in a larger contemporary sample and to demonstrate analytic uses of the newly available Project Data Sphere online resource, we used data from control arms of completed clinical trials to compare survival and toxicity among patients with postdocetaxel mCRPC treated with mitoxantrone and prednisone. PATIENTS AND METHODS: Control arm data from two phase III randomized control trials, SUN 1120 and TROPIC, were used to examine the efficacy of mitoxantrone plus prednisone (n = 305) versus prednisone alone (n = 257) among patients with postdocetaxel mCRPC. Propensity score matching was used to balance patient characteristics between the separate trials, conditioned on age and key prognostic variables of survival. The primary outcome was overall survival. Secondary endpoints evaluated safety. RESULTS: Median survival was similar among patients receiving mitoxantrone plus prednisone versus prednisone alone (385 days vs. 336 days; deceleration factor = 0.04; 95% confidence interval: -0.12 to 0.22). Prevalence of several any-grade toxicity, including fatigue, back pain, and peripheral neuropathy, was increased among patients who received mitoxantrone. CONCLUSION: There was no significant survival benefit for mitoxantrone plus prednisone over prednisone alone among men with mCRPC after docetaxel therapy. This finding is consistent with prior studies showing no survival advantage with mitoxantrone in the predocetaxel setting. Furthermore, our data suggest that mitoxantrone may be associated with increased toxicity compared with prednisone alone.