PSA response and cabazitaxel outcomes stratified by prior docetaxel PSA response in metastatic castrate-resistant prostate cancer (mCRPC).

119 Background: In the TheraP trial, both cabazitaxel and lutetium Lu 177 vipivotide textraxetan demonstrated similar overall survival (OS) in patients with mCRPC previously treated with docetaxel. We seek to identify predictors for cabazitaxel benefit by evaluating patients’ cabazitaxel outcomes in the context of prior docetaxel outcomes. Methods: We identified patients who started cabazitaxel after January 2010 at our institution. Patients were included if they received docetaxel for mCRPC but excluded if they received docetaxel for hormone-sensitive disease, used taxane in combination with other agents (e.g. carboplatin), or received multiple courses of same taxane (e.g. “re-challenges”). For adequate assessment of PSA response, patients were only included if pre-chemo PSA was > 20 ng/mL and had received at least two cycles of both taxanes. PSA response was defined as >50% decrease from baseline sustained for at least 3 weeks (PSA50). OS was calculated from time of cabazitaxel start to death from any cause. Results: Eighty patients were identified with a median age of 70 years at cabazitaxel start. Forty (50%) patients had a PSA50 with docetaxel, while only 18.8% had a PSA50 with subsequent cabazitaxel. Patients who had a PSA50 to docetaxel had a significantly higher chance of PSA50 to cabazitaxel (OR 5.29, 95% CI: 1.36, 20.53, p = 0.0162); the PSA50 rates on cabazitaxel were 30% and 7.5% between those that did and did not have a PSA50 to docetaxel, respectively. There were no significant differences in cabazitaxel median OS based on prior docetaxel PSA50. Conclusions: Patients who had PSA50 to docetaxel had a significantly higher chance to have a PSA50 to cabazitaxel. Prior docetaxel PSA50 could be considered when deciding whether to use cabazitaxel or an alternative agent for subsequent treatment. Table: see text