Oncologic Outcomes After Treatment for MRI Occult Breast Cancer (pT0N+).

BACKGROUND: Studies assessing outcomes in occult breast cancer have often included women treated before the routine use of magnetic resonance imaging (MRI). This study examined outcomes for patients presenting with axillary adenopathy and no primary breast tumor detectable by MRI or other imaging methods.

METHODS: All patients with axillary nodal metastases consistent with breast carcinoma and no breast primary tumor detectable by physical exam, mammography, or MRI treated between 1 January 1996 and 30 June 2011 were identified from an institutional database. Data were collected on local, regional, and distant recurrences.

RESULTS: For the study, 38 patients were identified. Modified radical mastectomy (MRM) was performed for 13 of the patients, whereas 25 of the patients underwent axillary dissection (ALND) and whole-breast radiotherapy (WBRT). Most of the women had pathologic N1 disease [median number of positive nodes, 2 (MRM cohort) and 3 (ALND + WBRT cohort); p = 0.38]. All the patients received chemotherapy, and 30 (79%) of the 38 patients received an anthracycline and taxane. Regional nodal radiation was used for 60% of those with ALND + WBRT and for all 46% of the MRM patients who received chest wall radiotherapy. During a median follow-up period of 7 years, there were no nodal recurrences. Two patients treated with ALND + WBRT had in-breast recurrences, whereas none in the MRM group experienced a local recurrence. The proportion that experienced distant disease was similar between the MRM cohort (1 of 13) and the ALND + WBRT cohort (2 of 25).

CONCLUSION: Breast cancer presenting as axillary adenopathy with no detectable primary tumor is rare. Breast conservation with WBRT is a viable option for patients with a diagnosis of occult breast cancer and a negative preoperative MRI.