From the Journals

Anastrozole/fulvestrant prolongs OS in metastatic ER+ breast cancer



For women with metastatic hormone receptor–positive breast cancer, the addition of the selective estrogen receptor modifier fulvestrant (Faslodex) to the aromatase inhibitor anastrozole (Arimidex and generics) resulted in a small but significant improvement in overall survival, according to final results from a randomized phase 3 trial.

Among 694 patients randomized for whom data were available, the hazard ratio for death with the combination when compared with anastrozole alone was 0.82 (P = .03), reported Rita S. Mehta, MD, from the University of California (Irvine) Medical Center and her colleagues.

The benefit of the combination was highest for patients without prior exposure to adjuvant endocrine therapy.

“Furthermore, sequential therapy with anastrozole and fulvestrant (45% of patients crossed over to fulvestrant alone) did not negate the significance of the long-term overall survival benefit with the combination therapy as compared with anastrozole,” the investigators wrote in The New England Journal of Medicine.

The current report is the final survival analysis of the trial. The primary results were reported in 2012 (N Engl J Med. 2012; 367:435-44). A total of 707 postmenopausal women with previously untreated metastatic disease were randomly assigned to receive either 1 mg of anastrozole orally every day with crossover to fulvestrant alone strongly encouraged if the disease progressed or to anastrozole and fulvestrant in combination. Randomization was stratified according to prior adjuvant tamoxifen use. A total of 694 women had data available for analysis.

The primary analysis, conducted at a median follow-up of 35 months, showed a median progression-free survival (PFS) with anastrozole alone of 13.5 months, compared with 15.0 months for anastrozole/fulvestrant (HR for progression or death 0.80; P = .007). Respective median overall survival was 41.3 months and 47.7 months (HR for death 0.81; P = .05).

The current, final analysis, conducted at a median follow-up of 7 years in patients who did not have disease progression, showed 261 deaths among 345 women (76%) in the anastrozole-only group, compared with 247 deaths among 349 women (71%) in the combination group (HR for death 0.82; P = .03).

Overall survival was longer for those women who had not previously received tamoxifen who were treated with the combination, at a median of 52.2 months versus 40.3 months for women not previously treated with tamoxifen who received anastrozole alone (hazard ratio, 0.73; 95% confidence interval, 0.58-0.92). In contrast, there was no significant difference in OS between the two treatment groups in women who had previously received tamoxifen.

Approximately 45% of patients initially randomized to anastrozole alone were crossed over to fulvestrant.

The incidence of long-term toxic effects and treatment-related deaths was similar between the groups. Previously reported treatment-related deaths with the combination included pulmonary emboli in two patients and a cerebrovascular ischemic event in one patients.

At the time of data cutoff for the final report, 15% of patients in the combination-therapy group and 13% in the anastrozole-only group had experienced grade 3 toxicities.

The study was supported by National Cancer Institute grants and by AstraZeneca. Dr. Mehta reported institutional and personal grants from AstraZeneca and others. Multiple coauthors reported similar relationships.

SOURCE: Mehta RS et al. N Engl J Med. 2019;380:1226-34.

Next Article: