Background: In men with metastatic castration resistant prostate cancer (CRPC),the association of measurable tumor responses with overall survival (OS) is unknown. We retrospectively evaluated the TAX327 phase III trial to study this relationship.
Methods: Eligible patients for this analysis included those with WHO-defined measurable metastatic disease randomized to receive either docetaxel or mitoxantrone. OS was estimated using the Kaplan-Meier method and the prognostic relationship of WHO-defined radiologic response with OS was performed using Cox proportional hazards regression. Landmark analyses evaluated survival from baseline and 2, 3, 4 and 6 months after baseline.
Results: Four hundred and twelve patients enrolled on the TAX327 trial had measurable tumors. Thirty-seven patients exhibited a complete or partial objective response (CR/PR, 9.0%), 116 had stable disease (SD, 28.2%), 99 had progressive disease (PD,24%) and 160 (38.8%) did not have a post-baseline objective assessment. Partial responders demonstrated longer median OS (29.0 months) than patients with SD (22.1 months), or those with PD (10.8 months) or those who were not assessed (12.7 months). These results remained after landmark analysis. We found a significant association between ≥30% PSA declines and radiologic response, with ≥30% PSA declines occurring in all patients with CR/PR, 79.8% of patients with SD and 34.4% with PD. Radiologic response remained a significant but modest post-treatment prognostic factor for OS after adjusting for treatment, pain-response and ≥30% PSA-decline (p=0.009).
Conclusions: In men with metastatic CRPC and measurable disease receiving chemotherapy, objective tumor response was prognostic for OS, and appears to complement PSA assessment.
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