Development of enzalutamide for metastatic castration-resistant prostate cancer

Influence of statins in metastatic castration-resistant prostate cancer patients treated with new antiandrogen therapies: a systematic review and meta-analysis

Objective

To evaluate whether the addition of statins to the new antiandrogens (enzalutamide or abiraterone) affects overall survival in patients with metastatic castration-resistant prostate cancer.

Methods

We searched studies in English language including the keywords statins, overall survival, and metastatic castration-resistant prostate cancer, at PubMed^® (MEDLINE^®), Embase and Cochrane databases.

Results

A total of 195 articles were initially identified, but only four met the inclusion criteria and were selected for the meta-analysis. A total of 955 patients, 632 on the new antiandrogens only group, and 323 on the new antiandrogens + statins group, were analyzed. In all four studies the combination therapy (new antiandrogens + statin) was well tolerated, regardless of which new antiandrogens were used. Neither the type of statin nor the doses and duration of use were well specified in the studies. The combination therapy in metastatic castration-resistant prostate cancer was associated with an overall survival improvement, and a 46% reduction in death (hazard ratio of 0.54; 95%CI 0.34-0.87; p<0.01) in multivariate analysis.

Conclusion

There seems to be a clinical benefit with the association of statins to the new antiandrogens in patients with metastatic castration-resistant prostate cancer, suggesting longer overall survival with no important collateral effect. However, due to fragility of the studies available in the literature, we are not yet capable of recommending this combination of drugs in the clinical practice. Further randomized prospective studies are warranted to confirm these beneficial outcomes.

New horizons in the management of castrate-resistant prostate cancer

Castrate-resistant prostate cancer is an incurable disease. It continues to be an area of intense research to save prostate cancer patients’ lives. We aim from this review to explore the new lines of treatment that aim at extending disease-specific survival. We conducted a PubMed research on available literature pertaining to key words alone and in combination: prostate cancer, castrate-resistant, immunotherapy, hormonal therapy, chemotherapy, radiation therapy, metastasis, survival and quality of life. We also reviewed the following guidelines on castrate-resistant prostate cancer: National Comprehensive Cancer Network (NCCN), American Urological Association (AUA), the National Institute for Health and Care Excellence (NICE) and the European Association of Urology (EAU). There are four new lines of treatment in castrate-resistant prostate cancer. An immunotherapy, sipuleucel T (Provenge); new hormonal therapies – in the form of a new androgen receptor blocker, enzalutamide (Xtandi) and new adrenal androgen synthesis inhibitor, abiraterone acetate (Zytiga); a new chemotherapy, cabazitaxel (Jevtana) and new radioactive agent, radium 223 (Xofigo). There is an agreement between guidelines that patients with M0 castrate-resistant prostate cancer should not be offered any of these treatments. Similarly, patients with castrate-resistant prostate cancer and poor performance status should be offered only palliative care. There are several new lines of treatment that can be used in castrate-resistant prostate cancer, and hopefully in the near future castrate-resistant prostate cancer will be changing from a lethal disease to more of a chronic disease.

Statin use and survival in patients with metastatic castration-resistant prostate cancer treated with abiraterone or enzalutamide after docetaxel failure: the international retrospective observational STABEN study

Background

Statins may potentiate the effects of anti-hormonal agents for metastatic castration-resistant prostate cancer (mCRPC) through further disruption of essential steroidogenic processes. We investigated the effects of statin use on clinical outcomes in patients with mCRPC receiving abiraterone or enzalutamide.

Materials and methods

This was a retrospective multicenter study including patients that received abiraterone or enzalutamide for mCRPC. The effect of concurrent statin use on outcomes was evaluated. The associations of statins with early (≤12 weeks) prostate-specific antigen (PSA) declines (> 30%), cancer-specific survival and overall survival (OS) were evaluated after controlling for known prognostic factors.

Results

Five hundred and ninety-eight patients treated with second-line abiraterone or enzalutamide after docetaxel for mCRPC were included. A total of 199 men (33.3%) received statins during abiraterone/enzalutamide treatment. Median OS was 20.8 months (95% CI = 18.3–23.2) for patients who received statins, versus 12.9 months (95% CI = 11.4–14.6) for patients who did not receive statins (P < 0.001). After adjusting for age, alkaline phosphatase, PSA, neutrophil-to-lymphocytes ratio, Charlson comorbidity score, Gleason score, visceral disease, hemoglobin, opiate use and abiraterone versus enzalutamide treatment, the use of statin therapy was associated with a 53% reduction in the overall risk of death (hazard ratio [HR] = 0.47; 95% CI = 0.35–0.63; P < 0.001). Statin use was also associated with a 63% increased odds of a > 30% PSA decline within the first 12 weeks of treatment (OR = 1.63; 95% CI = 1.03–2.60; P = 0.039).

Conclusions

In this retrospective cohort, statin use was significantly associated with both prolonged OS and cancer-specific survival and increased early > 30% PSA declines. Prospective validation is warranted.

PSA declines and survival in patients with metastatic castration-resistant prostate cancer treated with enzalutamide: A retrospective case-report study

RATIONALE

PSA responses have been associated with a survival benefit in patients treated with enzalutamide in retrospective analyses.

PATIENT CONCERNS

However the prognostic value of PSA declines in highly pretreated patients receiving enzalutamide remains to be defined.

DIAGNOSES AND INTERVENTATIONS

Medical records of patients with documented mCRPC treated with enzalutamide between September 2011 and August 2016 were reviewed at multiple participating centers and assessed for overall survival (OS), PSA variations, and other variables of interest. Univariable and multivariable analyses were conducted.

OUTCOMES

A total of 129 patients received enzalutamide. PSA response rates (>50% PSA declines) were 58/119 (48.7%), 58/115 (50.4%), 54/110 (49.1%), and 47/91 (51.7%) at weeks 4, 8, 12, and 16, respectively. Having a PSA response was a statistically significant prognostic factor of improved OS at 8 and 12 weeks in univariable analysis, whereas it was significant at 12 weeks in the multivariable analysis. Patients treated with enzalutamide had a median OS of 7.8 months.

LESSONS

Our study supports the prognostic value of PSA declines in heavily treated patients receiving enzalutamide.

Sipuleucel-T and Androgen Receptor-Directed Therapy for Castration-Resistant Prostate Cancer: A Meta-Analysis

New treatments, such as sipuleucel-T and androgen receptor- (AR-) directed therapies (enzalutamide (Enz) and abiraterone acetate (AA)), have emerged and been approved for the management of castration-resistant prostate cancer (CRPC). There are still debates over their efficacy and clinical benefits. This meta-analysis aimed to investigate the efficacy and safety of sipuleucel-T and AR-directed therapies in patients with CRPC. RevMan 5.1 was used for pooled analysis and analysis of publication bias. Seven studies were included in the meta-analysis, with three studies in sipuleucel-T (totally 737 patients, 488 patients in treatment group, and 249 patients in placebo group) and four in AR-directed therapies (totally 5,199 patients, 3,015 patients in treatment group, and 2,184 patients in placebo group). Treatment with sipuleucel-T significantly improved overall survival in patients with CRPC and was not associated with increased risk of adverse event of grade ≥3 (p > 0.05). However, treatment with sipuleucel-T did not improve time-to-progression and reduction of prostate-specific antigen (PSA) level ≥50% was not significantly different from that with placebo. AR-directed therapies significantly improved overall survival in patients with CRPC and improved time-to-progression and reduction of PSA level ≥50%. AR-directed therapies did not increase risk of adverse event of grade ≥3 (p > 0.05).