Invasive lobular
cancer (ILC) responds poorly to
neoadjuvant chemotherapy but appears to respond well to endocrine
therapy. We examined the effectiveness of neoadjuvant
letrozole in postmenopausal women (PMW) with
estrogen receptor (ER)-rich ILC. PMW were considered for treatment with neoadjuvant
letrozole if they had ER-rich, large operable, or locally advanced
cancers, or were unfit for surgical
therapy.
Tumor volume was estimated at diagnosis and at 3 months using calipers (clinical), ultrasound, and mammography. At 3 months, if physically fit, women were assessed for surgery. Responsive women with
cancers too large for
breast-conserving surgery continued with
letrozole. Patients had surgery or were switched to alternative
therapy if
tumor volume was increasing. Sixty-one patients (mean age, 76.2 years) with 63 ILCs were treated with
letrozole for ≥ 3 months. The mean reduction in
tumor volume at 3 months was 66% (median, 76%) measured clinically, 61% (median, 73%) measured by ultrasound, and 54% (median, 60%) measured by mammography. Surgery was possible at 3 months in 24
cancers in 24 patients, and all but two of the remaining patients continued with
letrozole therapy for a median duration of 9 months. At the time of this publication, 40 patients with a total of 41
cancers have undergone surgery. The rate of successful breast conservation was 81% (25/31). Twenty-one patients have continued with
letrozole monotherapy, and 19 remain controlled on
letrozole at a median of 2.8 years. There is a high rate of response to
letrozole in PMW with ER-rich ILC.