Background: Neoadjuvant endocrine therapy demonstrated activity in endocrine responsive locally advanced breast cancer. Proper duration of neoadjuvant therapy has not yet established. We aimed to assess the efficacy and safety of longer duration of letrozole alone or combined with triptorelin in pre-or postmenopausal breast cancer patients.

Methods: Premenopausal and postmenopausal patients (pts) with ER and PgR-positive > 50% of the cells, HER2-negative, T2-T4b breast cancer were considered eligible. Patients received letrozole 2,5 mg per day (plus triptorelin 3,75 mg/month in premenopausal pts) for 3-9 months. Tumor response was measured by caliper, ultrasound (US) and mammography. The primary endpoint was overall tumour response (ORR) (complete response plus partial response), during the neoadjuvant treatment period for the intention-to-treat population.

Results: Between 2009 and 2013, 54 pts were enrolled and 46 (34 pre- and 12 post-menopausal) pts were evaluable for ORR. Median age was 44 and 55 years, respectively. 44 patients are evaluable. The ORR was 77% in the premenopausal group and 67% in the postmenopausal group. One premenopausal patient had a pathological complete response (pCR). The mean time to complete/partial response was 4.9 months (95% CI: 3.8-6.0) in the premenopausal group and 3.6 months (95% CI: 0.8-6.4) in the postmenopausal group. Overall, 56% of premenopausal and 58% of postmenopausal pts underwent breast conservative surgery. Ki67-LI after surgery had a mean decrease of 33% (95% CI: 16%-50%, p-value = 0.0005) and 42% (95% CI: 18%-65%, p-value = 0.0030) in pre-and postmenopausal pts, respectively. Therapy was well tolerated in both groups with no grade 3/4 toxicity. The most common adverse events in both groups were hot flashes, fatigue, arthralgias/stiffness, and myalgias.

Conclusions: The results of this preliminary analysis support neoadjuvant endocrine therapy for a duration of up to 9 months. The combination of letrozole plus triptorelin might represent an alternative neoadjuvant treatment option for premenopausal women with early stage endocrine-responsive breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-15-03.