Testosterone levels in metastatic castration-resistant prostate cancer (mCRPC).

191 Background: It is common practice to continue anti-androgen therapy in terms of androgendeprivation when performing chemotherapy or androgendeprivation with new second generation therapeutic agents such as enzalutamide or abiraterone acetate. Clinical Studies aiming at the question whether continuation of conventional ADT is necessary in this setting are currently recruiting. In this study we analyzed androgen deprivation in patients with mCRPC under chemotherapy and second generation androgen suppression. Methods: Out of 620 screened patients a total of 36 patients with continuous testosterone monitoring and mCRPC underwent therapy with docetaxel, abiraterone acetate, enzalutamide, carboplatin, carbozantinib or cabazitaxel and were evaluated. Data were gathered from our center over a median follow up period of 27.8 (0.6 - 65.1) month. A cutoff of 0.5 ng/dL was used to discriminate patients according to testosterone castration levels. Statistical evaluation was performed applying Kaplan Meier survival estimates, Cox regression and log rank test. Results: Median follow up was 26.2 month (range 1.4 - 64.8 month). Mean patient age was 70.9 years (range 51 - 86 years). The mean testosterone concentration in our cohort was 0.5 ng/dL. Serum testosterone levels varied greatly: ranging from 0 to 16 ng/dL. A total of 18 patients died during follow up. Median survival over all patients according to Kaplan-Meier survival estimation was 38.7 month (95% CI: 31 - NA month). Median survival for patients with testosterone levels below and above 0.5 ng/dL were 48.67 and 18.13 month respectively (log rank test: p = 0.0029). In Cox regression analysis, the hazard ratio for risk of death for patients with testosterone concentrations > 0.5ng/dL was 6.03 (95% CI: 1.5 - 25, p - 0.0132). For the covariates PSA velocity, patient age and primary Gleason score there was no significant effect on risk of death (p = 0.0597, 0.5006, 0.7354). Conclusions: In patients with mCRPC i.e rising PSA or progression under androgen deprivation, conventional suppression of testosterone levels still represents a vital factor for overall survival even at the mCRPC stage and under therapy with second line anti hormonal therapeutic medication and chemotherapy.