The Effects of Neoadjuvant Anastrozole (Arimidex) on Tumor Volume in Postmenopausal Women with Breast Cancer: A Randomized, Double-Blind, Single-Center Study

Abstract

Anastrozole, an orally active, nonsteroidal aromatase inhibitor, was evaluated in a randomized, double-blind, single-center study to determine its efficacy as neoadjuvant therapy in postmenopausal women with newly diagnosed, estrogen receptor-rich, locally advanced or large (>3 cm), operable breast cancers. Twenty-four eligible patients were recruited into the study and received either 1 mg (n = 12) or 10 mg (n = 12) of anastrozole daily over a 3-month period. Tumor volumes were estimated clinically, by using caliper measurements and ultrasound (at baseline and after 1, 2, and 3 months’ treatment) and by mammography (at baseline and after 3 months). Tumor volume was also measured in surgical specimens. Twenty-one patients were classified as T₂, two patients as T₃, and one patient as T_4B at baseline. Three patients had clinical evidence of lymph node involvement. When considering the difference between the volume as measured by each assessment and the actual pathological volume, the interquartile range and the difference between the maximum and minimum values were smaller for ultrasound when compared with those measured with calipers and mammography. Therefore, of the three clinical assessments of tumor volume used in this study, the data suggest that ultrasound may be the most accurate. The median reductions in tumor volumes as measured by ultrasound for those patients with a measurable 12-week assessment were 80.5 and 69.6% for anastrozole (1 and 10 mg, respectively) after 12 weeks of treatment and 75.5% when both doses were grouped together. Moreover, of these patients, 11 of 12 given 1 mg and 7 of 11 given 10 mg of anastrozole were found on ultrasound to have a >50% reduction in tumor volume after 12 weeks of treatment. Of the 17 patients who would have required a mastectomy at initiation of treatment, 15 were suitable for breast conservation after anastrozole treatment. These results suggest that anastrozole is highly effective as neoadjuvant therapy in postmenopausal women with estrogen receptor-rich, large, operable breast cancer. Future studies comparing anastrozole with tamoxifen as a neoadjuvant treatment should be considered.