First-line enzalutamide, docetaxel combination improves disease control in advanced prostate cancer

SAN FRANCISCO — The addition of enzalutamide to docetaxel improved 6-month disease control and prolonged PFS as first-line therapy for men with metastatic castration-resistant prostate cancer, according to results from the CHEIRON study presented at Genitourinary Cancers Symposium.

“This is the first randomized phase 2 trial testing the addition of a new-generation androgen receptor-targeting agent to docetaxel,” Orazio Caffo, MD, senior assistant and chief of day hospital in the department of medical oncology at Santa Chiara Hospital, said during his presentation.

The analysis included 246 patients (median age, 70 years; range, 44-88) with metastatic castration-resistant prostate cancer. Fifty-four patients reported pain, and 50 patients had visceral metastases.

Researchers randomly assigned patients to receive 75 mg/m² IV docetaxel every 3 weeks plus androgen deprivation therapy for eight courses alone (n = 126) or with 160 mg daily enzalutamide (Xtandi; Astellas, Pfizer Oncology) for 24 weeks (n = 120).

The proportion of patients without disease progression at 6 months served as the study’s primary endpoint.

More patients assigned the combination of enzalutamide and docetaxel did not have disease progression at 6 months than patients assigned docetaxel alone (89.1% vs. 72.8%; P = .002; RR = 1.22; 95% CI, 1.08-1.38).

Median PFS was 10.1 months in the combination group and 9.1 months in the docetaxel group, which, although only a difference of 1 month, met statistical significance (HR = 0.71; 95% CI, 0.54-0.94).

Researchers did not observe a difference in OS, although the data are still immature as most of the patients remain alive, Caffo said. Median OS was 33.7 months with docetaxel and 29.6 months with the combination (HR = 1.13; 95% CI, 0.75-1.71).

“Although the control arm disease control rate was higher than expected, the trial met its primary endpoint,” Caffo said. “Our results show that the combination was feasible and safe, provided a better disease control rate than docetaxel alone, and did not improve OS.” – by Alexandra Todak

Reference:

Caffo O, et al. Abstract 148. Presented at: Genitourinary Cancers Symposium; Feb. 14-16, 2019; San Francisco.

Disclosures: Caffo reports honoraria from Astellas Pharma, Bayer, Janssen Oncology and Sanofi, and consultant/advisory roles with Astellas/Medivation and Janssen. Please see the abstract for all other authors’ relevant financial disclosures.