OBJECTIVES: Endocrine treatment for breast cancer acts largely by inhibiting tumor cell proliferation. This study aimed to determine the efficacy of short-term neoadjuvant endocrine therapy by response on Ki67-index in early-stage breast cancer.

METHODS: A prospective series of 40 patients with early N0/N1 breast cancer were reviewed. Within the time gap between the primary diagnosis and their surgery, postmenopausal women were subjected to take Letrozole 2.5mg once daily, wherein premenopausal women to Tamoxifen 20mg once daily. The fall in Ki67 after the endocrine therapy was defined as the percentage of difference between the pre and post operative Ki67 value with the preoperative Ki67.

RESULTS: Among forty subjects, 28(70%) were postmenopausal and 12(30%) were premenopausal women. Mean age was 46.17±6.073 and 64.79±8.293 in pre and postmenopausal women respectively. In premenopausal women whose initial mean Ki67 was 34.850±21.761, received tamoxifen preoperatively with a mean duration of 15.92±3.704 days. Wherein, postmenopausal women’ initial mean Ki67 was 33.214±22.3472 and received letrozole for a mean duration of 18.59±9.022 days. 70.0% of premenopausal women had an increase in Ki67 and 20.0% had a fall in ki67 >80% after preoperative therapy. In patients who received letrozole 11.1% had an increase in Ki67 after therapy, whereas 33.3% had a fall in ki67 >80%. There was significant correlation between the fall in Ki67 with progesterone receptor (PR) expression (p value 0.003) and estrogen receptor (ER) expression (p value 0.035). There was no significant correlation between the fall in ki67 index and the duration endocrine therapy (p value 0.197)

CONCLUSIONS: Short-term changes in Ki67 index in the neoadjuvant settings may predict outcome during adjuvant use of same treatment. The data indicate that tamoxifen may not be an effective choice of therapy in neoadjuvant setting, wherein letrozole has a marked effectiveness in preoperative therapy in patients with ER/PR positive untreated breast cancer.