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.
