Statistical Analyses Confirm Benefit of Cabazitaxel Over Abiraterone or Enzalutamide in mCRPC

Bertrand Tombal, MD, PhD

Stratified multivariate analysis as well as efficacy from multiple treatment time points confirmed the benefit of cabazitaxel (Jevtana) over abiraterone acetate (Zytiga) or enzalutamide (Xtandi) as a standard treatment in men with metastatic castration-resistant prostate cancer (mCRPC) who were previously treated with docetaxel and either of those 2 androgen receptor (AR)-targeted agents, according to results presented during the 2020 American Society of Clinical Oncology Virtual Scientific Program.¹

In a poster, study authors, led by Bertrand Tombal, MD, PhD, professor and chairman of urology at the Université catholique de Louvain, Cliniques universitaires Saint-Luc in Brussels, Belgium, determined the robustness of the overall survival benefit that was previously published in the CARD (NCT02485691) trial.^1,2

CARD was a multicenter, randomized, open-label study evaluating patients with mCRPC who had progressed within 12 months of receiving an AR-targeted therapy before or after docetaxel.²

Patients were randomized 1:1 to therapy with cabazitaxel (25 mg/m2 every 3 weeks) plus prednisone (10 mg daily) or either control regimen of abiraterone (1000 mg once daily) plus prednisone (5 mg twice daily) or enzalutamide (160 mg once daily), depending on which agent they had previously received. Patients in the cabazitaxel arm also received granulocyte colony-stimulating factor.

Cabazitaxel improved median radiographic progression-free survival by over 4 months (8.0 months with cabazitaxel vs 3.7 months with abiraterone or enzalutamide [HR, 0.54; 95% CI, 0.40-0.73; P <.0001]). Median OS with cabazitaxel was 13.6 months compared with 11.0 months for patients receiving abiraterone or enzalutamide (HR, 0.64; 95% CI, 0.46-0.89; P =.0078).2

In the current analysis, OS was determined from the date of diagnosis of metastatic disease, date of mCRPC diagnosis, and time of initiation of first and second life-extending therapy (LET). Prognostic factors affecting OS were evaluated using univariate analysis and a stepwise multivariate Cox regression analysis.

The investigators identified M1 disease at diagnosis, visceral metastases, Gleason score between 8 to 10 at diagnosis, prior therapy with curative intent, and type of progression as categorical covariates. Continuous covariates included hemoglobin, prostate-specific antigen (PSA), lactate dehydrogenase (LDH) levels, alkaline phosphatase levels, neutrophil-to-lymphocyte ratio, neutrophil count, and testosterone.

Patient baseline characteristics showed median age was 70 years and the majority of patients had metastases to bone: 83.3% in the cabazitaxel arm (n =129) and 88.0% in the abiraterone or enzalutamide arm (n = 126). In the cabazitaxel arm at prior LET, 43.4% received abiraterone and 55.8% received enzalutamide. In the abiraterone and enzalutamide arm, 53.2% received abiraterone and 46.8% received enzalutamide.

When reviewing data from metastatic disease diagnosis, the investigators reported that cabazitaxel conferred a median OS of 54.7 months compared with 42.5 months for either abiraterone or enzalutamide. Reviewing OS from the date of mCRPC diagnosis, patients receiving cabazitaxel had a median OS of 40.9 months compared with 31.3 months for abiraterone or enzalutamide.

Patients who received cabazitaxel were also favored for OS from first and second LET initiation compared with patients who received abiraterone or enzalutamide. Median OS for first LET in the cabazitaxel arm was 36.4 months versus 30.5 months in the abiraterone or enzalutamide arm. Corresponding rates from the second LET initiation showed medians of 24.2 versus 21.9 months.

Univariate analysis revealed that higher neutrophil-to-lymphocyte ratio, higher PSA levels, lower hemoglobin values, higher LDH values, higher alkaline phosphatase values, and higher neutrophil count were associated with worse OS (TABLE 1).¹

Table 1. Univariate analysis of OS in CARD Trial¹

_{LDH, lactate dehydrogenase; OS, overall survival; PSA, prostate-specific antigen}

Multivariate analysis revealed that high neutrophil-to-lymphocyte ratio, low hemoglobin level, and high PSA levels were associated with worse OS (TABLE 2).¹

Table 2. Multivariate analysis of OS in CARD Trial¹

_{OS, overall survival; PSA, prostate-specific antigen}

In conclusion, the investigators wrote that the survival benefit of the treatment sequence, docetaxel and one AR-targeted agent followed by cabazitaxel, was consistent for any treatment starting point, which was confirmed by stratified multivariate analysis.

_References

_{1. Tombal B, Castellano D, Kramer G, et al. CARD: Overall survival (OS) analysis of patients with metastatic castration-resistant prostate cancer (mCRPC) receiving cabazitaxel versus abiraterone or enzalutamide. J Clin Oncol. 2020;38(suppl 15):5569. doi:10.1200/JCO.2020.38.15_suppl.5569}

_{2. de Wit R, de Bono J, Sternberg CN, et al; CARD Investigators. Cabazitaxel versus abiraterone or enzalutamide in metastatic prostate cancer. N Engl J Med. 2019;381(26):2506-2518. doi:10.1056/NEJMoa1911206}

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