These results suggest that the best adjuvant endocrine treatment for chemotherapy-treated, ER+ breast cancer patients diagnosed aged 45-50 years, consists of mainly AI followed by a switch strategy and mainly tamoxifen.
All Dutch women who received adjuvant chemotherapy and endocrine treatment for stage I-III, ER + (>10% positive cells), invasive breast cancer, diagnosed between 2004-2007, were identified through the Netherlands Cancer Registry. Included women were considered perimenopausal based on an age at diagnosis of 45-50 years (n = 2,295). For each patient AI treatment duration relative to total endocrine treatment duration was calculated. Predominantly tamoxifen-treated patients (AI < 25%) were compared with those receiving AI and tamoxifen for a similar duration (AI 25%-75%) and those mostly using AI (AI > 75%). Adjusted hazard ratios (HRs) for recurrence-free survival (RFS) and overall survival (OS) were calculated using time-dependent Cox regression.
Benefit of adjuvant aromatase inhibitors (AI) versus tamoxifen has been investigated in randomized clinical trials for premenopausal and postmenopausal patients with early, estrogen receptor positive (ER+) breast cancer. The optimal endocrine treatment for chemotherapy-treated perimenopausal women, who generally develop chemotherapy-induced amenorrhea, is uncertain.
After an average follow-up of 7.6 years, 377 RFS events occurred. Women mostly receiving AI (AI > 75%) had the best RFS (adjusted-HR = 0.63; 95% confidence interval = 0.46-0.86) followed by those receiving AI 25%-75% (adjusted-HR = 0.85; 95% confidence interval = 0.65-1.12), when compared to predominantly tamoxifen-treated women. Trend analyses showed that every 10% increase in AI-endocrine treatment ratio reduced RFS event risk with 5% (2-sided Ptrend = 0.002). In total, 236 deaths occurred, hazard ratios for OS showed similar trends.