Purpose: Germline mutations in DNA damage repair (DDR) genes are identified in a significant proportion of patients with metastatic prostate cancer, but the clinical implications of these genes remain unclear. This prospective multicenter cohort study evaluated the prevalence and effect of germline DDR (gDDR) mutations on metastatic castration-resistance prostate cancer (mCRPC) outcomes. Patients and Methods: Unselected patients were enrolled at diagnosis of mCRPC and were screened for gDDR mutations in 107 genes. The primary aim was to assess the impact of ATM/BRCA1/BRCA2/ PALB2 germline mutations on cause-specific survival (CSS) from diagnosis of mCRPC. Secondary aims included the association of gDDR subgroups with response outcomes for mCRPC treatments. Combined progression-free survival from the first systemic therapy (PFS) until progression on the second systemic therapy (PFS2) was also explored. Results: We identified 68 carriers (16.2%) of 419 eligible patients, including 14 with BRCA2, eight with ATM, four with BRCA1, and none with PALB2 mutations. The study did not reach its primary end point, because the difference in CSS between ATM/BRCA1/BRCA2/PALB2 carriers and noncarriers was not statistically significant (23.3 v 33.2 months; P = .264). CSS was halved in germline BRCA2 (g BRCA2) carriers (17.4 v 33.2 months; P = .027), and g BRCA2 mutations were identified as an independent prognostic factor for CCS (hazard ratio [HR], 2.11; P = .033). Significant interactions between g BRCA2 status and treatment type (androgen signaling inhibitor v taxane therapy) were observed (CSS adjusted P = .014; PFS2 adjusted P = .005). CSS (24.0 v 17.0 months) and PFS2 (18.9 v 8.6 months) were greater in g BRCA2 carriers treated in first line with abiraterone or enzalutamide compared with taxanes. Clinical outcomes did not differ by treatment type in noncarriers. Conclusion: g BRCA2 mutations have a deleterious impact on mCRPC outcomes that may be affected by the first line of treatment used. Determination of g BRCA2 status may be of assistance for the selection of the initial treatment in mCRPC. Nonetheless, confirmatory studies are required before these results can support a change in clinical practice.

Plasma androgen receptor (AR) gain identifies metastatic castration-resistant prostate cancer (mCRPC) patients with worse outcome on abiraterone/enzalutamide, but its relevance in the context of taxane chemotherapy is unknown. We aimed to evaluate whether docetaxel is active regardless of plasma AR and to perform an exploratory analysis to compare docetaxel with abiraterone/enzalutamide. This multi-institutional study was a pooled analysis of AR status, determined by droplet digital polymerase chain reaction, on pretreatment plasma samples. We evaluated associations between plasma AR and overall/progression-free survival (OS/PFS) and prostate-specific antigen (PSA) response rate in 163 docetaxel-treated patients. OS was significantly shorter in case of AR gain (hazard ratio [HR]=1.61, 95% confidence interval [CI]=1.08-2.39, p=0.018), but not PFS (HR=1.04, 95% CI 0.74-1.46, p=0.8) or PSA response (odds ratio=1.14, 95% CI=0.65-1.99, p=0.7). We investigated the interaction between plasma AR and treatment type after incorporating updated data from our prior study of 73 chemotherapy-naïve, abiraterone/enzalutamide-treated patients, with data from 115 first-line docetaxel patients. In an exploratory analysis of mCRPC patients receiving first-line therapies, a significant interaction was observed between plasma AR and docetaxel versus abiraterone/enzalutamide for OS (HR=0.16, 95% CI=0.06-0.46, p<0.001) and PFS (HR=0.31, 95% CI=0.12-0.80, p=0.02). Specifically, we reported a significant difference for OS favoring abiraterone/enzalutamide for AR-normal patients (HR=1.93, 95% CI=1.19-3.12, p=0.008) and a suggestion favoring docetaxel for AR-gained patients (HR=0.53, 95% CI=0.24-1.16, p=0.11). These data suggest that AR-normal patients should receive abiraterone/enzalutamide and AR-gained could benefit from docetaxel. This treatment selection merits prospective evaluation in a randomized trial. PATIENT SUMMARY: We investigated whether plasma androgen receptor (AR) predicted outcome in metastatic castration-resistant prostate cancer (mCRPC) patients treated with docetaxel, and we performed an exploratory analysis in patients treated with docetaxel or AR-directed drugs as first-line mCRPC therapy. We showed that plasma AR normal favored hormonal treatment, whilst plasma AR-gained patients may have had a longer response to docetaxel, suggesting that plasma AR status could be a useful treatment selection biomarker.

The increasing knowledge of prostate cancer is leading to many questions about its natural history and to reconsider conventional therapeutic strategies. Androgen ablation therapy has been the standard therapy in the advanced setting. Although docetaxel has demonstrated increased survival in patients with metastatic prostate cancer who had progressed to hormone treatments, due to its potential toxicity the role of chemotherapy has been relegated to patients who were symptomatic or who had high tumor burden. Several studies have assessed whether docetaxel could have a role in hormone-sensitive disease or even in earlier stages with no distant metastases. In the CHAARTED and STAMPEDE studies, docetaxel provides an unprecedented increase in overall survival (OS). This review summarizes the evidence behind the paradigm shift to strengthening docetaxel as a new standard of treatment that prolongs survival in earlier stages of prostate cancer.

Despite the advent of immunotherapy in urothelial cancer, there is still a need to find effective cytotoxic agents beyond first and second lines. Vinflunine is the only treatment approved in this setting by the European Medicines Agency and taxanes are also widely used in second line. Cabazitaxel is a taxane with activity in docetaxel-refractory cancers. A randomized study was conducted to compare its efficacy versus vinflunine. This is a multicenter, randomized, open-label, phase II/III study, following a Simon’s optimal method with stopping rules based on an interim futility analysis and a formal efficacy analysis at the end of the phase II. ECOG Performance Status, anaemia and liver metastases were stratification factors. Primary objectives were overall response rate for the phase II and overall survival for the phase III. Seventy patients were included in the phase II across 19 institutions in Europe. Baseline characteristics were well balanced between the two arms. Three patients (13%) obtained a partial response on cabazitaxel (95% CI 2.7–32.4) and six patients (30%) in the vinflunine arm (95% CI 11.9–54.3). Median progression-free survival for cabazitaxel was 1.9 versus 2.9 months for vinflunine (P = 0.039). The study did not proceed to phase III since the futility analysis showed a lack of efficacy of cabazitaxel. A trend for overall survival benefit was found favouring vinflunine (median 7.6 versus 5.5 months). Grade 3- to 4-related adverse events were seen in 41% patients with no difference between the two arms. This phase II/III second line bladder study comparing cabazitaxel with vinflunine was closed when the phase II showed a lack of efficacy of the cabazitaxel arm. Vinflunine results were consistent with those known previously. NCT01830231.