Breast cancer statistics for Japan in 2022: annual report of the national clinical database-breast cancer registry—clinical implications including chemosensitivity of breast cancer with low estrogen receptor expression

This is an annual report by the Japanese Breast Cancer Society, which provides statistics on the clinical data on breast cancer in Japan, extracted from the National Clinical Database-Breast Cancer Registry (NCD-BCR). This report includes an update of 102,453 breast cancer cases at 1339 institutions registered in the NCD-BCR in 2022. Among the 101,793 female patients, the median age at cancer diagnosis was 62 years (interquartile range, 50-73 years), and 29.4% of the patients were premenopausal. Of these patients, 15,437 (15.2%) and 42,936 (42.2%) were diagnosed with stage 0 and I disease, respectively. Estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2) were positive in 78.7%, 69.4%, and 12.8% of the patients, respectively. Of the 97,154 patients without distant metastasis, 40,521 (41.7%) underwent breast-conserving surgery, and 5780 (5.9%) patients underwent some form of breast reconstruction procedures at the time of mastectomy. A total of 66,894 (68.9%) patients were treated with sentinel lymph node biopsy and 7155 (7.4%) patients were treated with sentinel lymph node biopsy followed by axillary node dissection. In the group of patients treated with breast-conserving surgery (n = 40,521), 29,500 (72.8%) received whole-breast irradiation. In the group of patients who underwent mastectomy (n = 54,476), 6226 (11.4%) received radiation therapy to the chest wall. Of the 13,950 patients receiving preoperative chemotherapy with or without molecular targeted therapy, 4308 (30.9%) achieved a pathological complete response, with the highest rate of 60.5% in patients with the hormone receptor-negative/HER2-positive subtype.