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Predictive factors for oligometastatic versus non-oligometastatic involvement of the central nervous system by brain metastases from breast cancer.
Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).
Background: To assess rates of oligometastatic (1-3 metastases) versus non-oligometastatic (4 or more) involvement of the central nervous system (CNS) from breast cancer and determine whether rates vary for different breast cancer subtypes. Methods: We reviewed records of 65 patients with brain metastases from breast cancer. Fisher’s Exact Test compared incidence of oligometastatic versus nonoligometastatic CNS involvement and presence of visceral metastatic disease between groups. Paired Student's t test compared mean age and interval from initial diagnosis to development of brain metastases. Results: 25 patients (38.5%) developed oligometastatic and 40 (61.5%) developed non-oligometastatic CNS disease. Subtypes predictive of oligometastatic disease included ER+ (p .04) and PR+ (p .008). Subtypes predictive of non-oligometastatic disease included HER2+ (p .05). HER2+ patients trended toward a lower incidence of visceral metastases compared to ER+ or PR+ patients (p .07). Non-oligometastatic and HER2+ patients developed brain metastases sooner after initial diagnosis (p .046 and .03, respectively). Conclusions: ER+ breast cancer patients are more likely to develop oligometastatic CNS involvement and may be excellent candidates for stereotactic radiosurgery (SRS) alone. HER+ patients are likely to develop non-oligometastatic CNS involvement and may be better treated initially with whole brain radiotherapy (WBRT) even with apparent initial oligometastatic CNS involvement.