Primary Endocrine Therapy for Estrogen Receptor–Positive Ductal Carcinoma in Situ
Breast magnetic resonance imaging (MRI) volume decreased markedly at 3 months in postmenopausal women with estrogen receptor–positive ductal carcinoma in situ (DCIS) when treated with 6 months of preoperative endocrine therapy. This finding from the Cancer and Leukemia Group B (CALGB 40903) phase II single-arm study was presented by Eun-Sil Shelley Hwang, MD, MPH, Vice-Chair of Research at Duke University Medical Center, and colleagues, at the 2017 San Antonio Breast Cancer Symposium (SABCS; Abstract GS5-05).
The investigators suggest these results may help determine whether MRI could be an effective modality for monitoring treatment response in some patients treated with primary endocrine therapy for this type of breast cancer.
A total of 66 patients were assessable. All patients underwent baseline mammography and MRI, followed by 6 months of preoperative endocrine therapy with letrozole. The primary endpoint—change in total MRI volume—decreased from baseline to 3 months by 1.93 cm3 (p<.001) and from baseline to 6 months by 1.82 cm3 (p<.001). At the end of the study, of women who underwent excision, the pathologic specimens showed a 9% pathologic complete response.
Secondary endpoints were change in MRI maximum diameter over baseline and change in mammographic extent of disease over baseline. There was no significant difference in tumor volume between 3 and 6 months, and the mammographic extent of disease was not altered significantly.