Clinical response at 4 months to neoadjuvant letrozole predicts distant disease free survival in postmenopausal women with stage II-III ER/PgR-positive breast cancer
10531 Background: Letrozole (L) is more active than tamoxifen in early stage ER[+] breast cancer both as adjuvant (BIG-98 trial) or neoadjuvant (LET-024) therapy. However, complete pathological remissions to neoadjuvant endocrine therapy are anecdotal (<5%), there are no new prognostic indicators with clinical implications. Methods: We have review our series of postmenopausal patients with stage II-III breast cancer ER/PgR[+] breast cancer treated in our institution with L as neoadjuvant therapy. All patients had completed 4 months of therapy (in the absence of PD), and had measurable clinical (or radiological) disease. An independent statistical analysis was conducted for disease free (DFS) and distant disease free survival (DDFS). Results: From IV/99 to XII/04, 107 patients fulfill the criteria. Median age 76 years (range 64 to 92); median tumour size 35 mm (range 25 to 100); cT2 75 (70%), cT3/4 32 (30%); cN[-] 83 (78%). The ORR (PR + CR) at 4 months was 63% (7 CR and 60 PR), 4 patients had PD as best response (4%) and 36 a SD (34%). Surgery was done in 63 patients (59%), including all non-responders. Only 2 patients received adjuvant CT. With a median follow-up of 32 month (range 8 to 66), 12 patients had relapsed (9 distant). The 3 years DFS and DDFS were 84% and 90% respectively. In univaried analysis: cN (p < 0.02), cT3/4 (p < 0.02), and clinical response at 4 months (CR) (p = 0.003) were related to DFS; and HER2 (p < 0.05), cN (p < 0.003), and CR (p = 0.007) with DDFS. Other factors like cT, HR-levels, or surgery were not significant. Multivariate analysis showed that only OR and cN remained independently predictive both for DFS and DDFS. Conclusions: Clinical response to neoadjuvant letrozole therapy is an independent predictor of distant disease free survival and could be of value to recommend or deny more aggressive therapies in addition to endocrine therapy. [Table: see text] No significant financial relationships to disclose.