Secondary breast surgery after initial partial mastectomy for breast cancer in Japan

Background: Partial mastectomy for breast cancer may be followed by unplanned secondary surgery due to adverse outcomes, such as the detection of positive margins or cancer recurrence, thus adding burden to patients, providers, and payers. We analyzed the prevalence of this outcome and its economic impact in Japan. Methods: We utilized the Medical Data Vision (MDV) Research Database to identify a cohort of women in Japan who underwent an index partial mastectomy between 2008 and 2023, following their healthcare encounters up to 5 years postoperatively, including any secondary partial or total mastectomies. Results: Overall, 49,659 patients with breast cancer underwent primary partial mastectomy, and 2,203 (4.4%) underwent a second surgery. Among these secondary procedures, approximately two-thirds were total mastectomies. The median five-year postoperative healthcare expenditure among patients with one primary partial mastectomy was ¥1.8 million, and ¥2.5 million among patients requiring more than one procedure. Secondary procedures were more common among younger patients, those with larger tumors, and those who did not receive neoadjuvant therapy. Conclusion: Partial mastectomy is an essential surgical treatment for early stage breast cancer in Japan. While secondary surgery rates are low compared with other countries, these procedures still have negative financial consequences and extend patients’ journeys to remission.