Oncologic Outcomes with Neoadjuvant Chemotherapy and Breast Conservation for MRI Occult Breast Cancer

Background: Occult primary breast cancer is a presentation of breast cancer involving lymph nodes without an identified primary tumor within the breast. Mastectomy with axillary node dissection has been the traditional management. However, reported oncologic outcomes with mastectomy have been similar to those with breast conserving therapy (axillary surgery and radiotherapy). With the increased sensitivity of MRI and its routine use in the workup of occult breast cancer, the role of mastectomy for occult breast cancer is now even less clear. We report our institutional experienc of neoadjuvant chemotherapy followed by axillary surgery and radiotherapy for women with occult breast cancer. Methods: We conducted a retrospective review of women diagnosed with isolated metastatic adenocarcinoma to the axilla histologically consistent with breast adenocarcinoma without evidence of a primary breast tumor. Medical records were analyzed to gather pertinent information regarding diagnostic workup, treatment, recurrence, and survival. Results: We identified seven patients treated in our institution between 2012 and 2017 who met the criteria for primary occult breast cancer. The median age at diagnosis was 63 years old (range 42-71). Subtypes by immunohistochemistry (IHC) were HER-2 positive (3 pts), triple negative (2 pts), and hormone receptor positive/HER-2 negative (2 pts). All patients received neoadjuvant chemotherapy and axillary surgery without mastectomy followed by adjuvant radiotherapy to the breast and regional nodes. Hormone receptor positive patients received adjuvant endocrine therapy. At a median follow-up of 3.5 years, all patients were alive with no local or regional recurrence of disease while one patient developed distant metastases. Conclusion: A multimodality approach with neoadjuvant chemotherapy can lead to high rates of breast conservation in women with primary occult breast cancer. This approach appears to be oncologically safe.