Overall Survival with Fulvestrant plus Anastrozole in Metastatic Breast Cancer

Abstract

BACKGROUND We previously reported prolonged progression-free survival and marginally prolonged overall survival among postmenopausal patients with hormone receptor–positive metastatic breast cancer who had been randomly assigned to receive the aromatase inhibitor anastrozole plus the selective estrogen-receptor down-regulator fulvestrant, as compared with anastrozole alone, as first-line therapy. We now report final survival outcomes. METHODS We randomly assigned patients to receive either anastrozole or fulvestrant plus anastrozole. Randomization was stratified according to adjuvant tamoxifen use. Analysis of survival was performed by means of two-sided stratified log-rank tests and Cox regression. Efficacy and safety were compared between the two groups, both overall and in subgroups. RESULTS Of 707 patients who had undergone randomization, 694 had data available for analysis. The combination-therapy group had 247 deaths among 349 women (71%) and a median overall survival of 49.8 months, as compared with 261 deaths among 345 women (76%) and a median overall survival of 42.0 months in the anastrozole-alone group, a significant difference (hazard ratio for death, 0.82; 95% confidence interval [CI], 0.69 to 0.98; P = 0.03 by the log-rank test). In a subgroup analysis of the two strata, overall survival among women who had not received tamoxifen previously was longer with the combination therapy than with anastrozole alone (median, 52.2 months and 40.3 months, respectively; hazard ratio, 0.73; 95% CI, 0.58 to 0.92); among women who had received tamoxifen previously, overall survival was similar in the two groups (median, 48.2 months and 43.5 months, respectively; hazard ratio, 0.97; 95% CI, 0.74 to 1.27) (P = 0.09 for interaction). The incidence of long-term toxic effects of grade 3 to 5 was similar in the two groups. Approximately 45% of the patients in the anastrozole-alone group crossed over to receive fulvestrant. CONCLUSIONS The addition of fulvestrant to anastrozole was associated with increased long-term survival as compared with anastrozole alone, despite substantial crossover to fulvestrant after progression during therapy with anastrozole alone. The results suggest that the benefit was particularly notable in patients without previous exposure to adjuvant endocrine therapy. (Funded by the National Cancer Institute and AstraZeneca; ClinicalTrials.gov number, .)

Breast Cancer, Version 3.2020, NCCN Clinical Practice Guidelines in Oncology

“…43 A subgroup analysis in this trial suggested that patients without prior adjuvant tamoxifen experienced the greatest OS benefit with combination therapy compared with monotherapy (median, 52.2 vs 40.3 months, respectively; HR, 0.73; 95% CI, 0.58-0.92). 44 The reasons for the divergent outcomes in these trials are not very clear. The 3 trials discussed previously had slightly different patient populations.…”

First-line endocrine therapy for postmenopausal patients with hormone receptor-positive, HER2-negative metastatic breast cancer: a systematic review and meta-analysis

“…The updated results of SWOG 0266 showed improvement in overall survival by combination therapy with anastrozole and AI, especially among patients without receiving previous endocrine therapy [20]. We did not include this finding, because our systematic review is restricted to the study published until 2016.…”

Drug repurposing for breast cancer therapy: Old weapon for new battle

“…Selective estrogen receptor degrader (SERD) such as fulvestrant, are pure anti-estrogens that blocks estrogen receptor and degrades the receptor without any agonist effect [120]. Fulvestrant was first used in 2002 as a 'SERD hormone therapy' against HR + HER2 − advanced and metastatic breast cancer in post-menopausal women that were resistant to other hormone therapy [121]. It is used in combination with CDK4/6 inhibitors like palbociclib (PALOMA-3) and ribociclib (MONALEESA-3) and anti-PI3K/AKT/mTOR pathway drugs such as pictilisib (FERGI) and buparlisib (BELLE-2 and BELLE-3) [122].…”