Follow-up interval for probably benign breast lesions on screening ultrasound in women at average risk for breast cancer with dense breasts

Background: Women at high risk for breast cancer and women at average risk have different pretest probabilities. Probably benign lesions on screening ultrasound (US) should be assessed and managed differently for these two risk groups. Purpose: To evaluate the effectiveness of short-term follow-up for probably benign lesions on screening US in women at average risk for breast cancer with dense breasts. Material and Methods: A total of 445 women at average risk for breast cancer with probably benign lesions on screening US, dense breasts, and negative or benign mammography results were included. Women were classified into the six-month group (n = 345) or 12-month group (n = 100) according to when the first follow-up was performed (3–9 months or 9–15 months). The cancer detection rate, frequencies of newly developed lesions and progressed lesions, and biopsy rate were compared. Results: There were no malignancies from three to 15 months. Three cancers newly developed after 15 months. One was a 3-mm ductal carcinoma in situ and two were 10-mm and 18-mm invasive ductal carcinoma without lymph node metastasis. The frequency of newly developed lesions and progressed lesions and biopsy rate were not significantly different between the six-month and 12-month groups (P = 0.320, 0.621, and >0.999). Conclusion: A follow-up at 12 months can be considered for probably benign lesions on screening US in women at average risk for breast cancer with dense breasts. However, a large series prospective study is needed before clinical application.