Maysa Tamara Silveira Vilbert
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Marcelle Goldner Cesca
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Natasha Carvalho Pandolfi
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Vinicius Fernando Calsavara
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Bruno Cezar de Mendonça Uchôa
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e17545 Background: Androgen receptor-targeted agents Abiraterone and Enzalutamide (Abi/Ez) prolonged overall survival in metastatic castration resistant prostate cancer (mCRPC). Patients with very-low serum testosterone levels seem to have less benefit from these therapies as well as more aggressive prostate cancer. Methods: A retrospective observational cohort study was conducted to evaluate whether a serum testosterone measured at time of start first-line therapy with Abi/Ez is related to overall survival (OS) and time-to-treatment failure (TTF) in mCRPC patients. Kaplan-Meier survival estimates and Cox-regression models were used for time-to-event analyses. The best cut-off for testosterone was defined using Log-rank statistics (Lausen and Schumacher). X² test and Mann-Whitney U-test were applied to compare categorical and continuous variables, respectively. Logistic regression was used to assess characteristics related to serum testosterone levels. Statistical significance was fixed at 0.05. Results: From May 2012 to February 2017, 100 patients were assessed. Median follow-up was 27.8 months (range 2.23 to 68.26). Pts with a high testosterone level ( > 28.2; n = 20) achieved a significantly higher OS (median 66.0 vs 31.9 mo, testosterone > 28.2 HR: 0.206, 95% CI 0.074 to 0.571, p = 0.002) and TTF (median 30.6 vs 11.8 mo, testosterone > 28.2 HR: 0.408, 95%CI 0.219 to 0.762, p = 0.005) than pts with a low serum testosterone level ( < 28.2; n = 80), regardless of receiving therapy with either Abi (n = 69) or Ez (n = 31). Pts with a higher testosterone level were younger (median 67.7 vs 73.6 years; p = 0.026), had a higher body mass index (BMI) (28.5 vs 25.9, p = 0.023) and a lower PSA at start Abi/Ez (12 vs 26, p = 0.031) than pts with lower values. Age (OR 0.93, 95%CI 0.8 to 0.9, p = 0.021), BMI (OR 1.21, 95%CI 1.1 to 1.4, p = 0.006) and baseline PSA (OR 1.2, 95%CI 1.03 to 1.4, p = 0.020) were significantly associated with testosterone > 28.2. After 4 months of Abi/Ez treatment, PSA decrease > 50% of baseline was seen more frequently in high testosterone levels group than in low testosterone levels pts (90% vs 57.5% of pts, respectively, p = 0.007). Conclusions: Pts with high levels of testosterone ( > 28.2) achieved a better OS and TTF when treated with Abi/Ez in first-line mCRPC than those with low levels. Testosterone can be considered a prognostic and predictive biomarker in this scenario, and could be used in treatment decision for this population.
Serum Testosterone Level to Predict the Efficacy of Sequential Use of Antiandrogens as Second-line Treatment Following Androgen Deprivation Monotherapy in Patients with Castration-resistant Prostate Cancer
