Preliminary experience of the concurrent use of radiosurgery and T-DM1 for brain metastases in HER2-positive metastatic breast cancer.

This is preliminary study assessing the efficacy and safety of concurrent use of radiation therapy (RT) and T-DM1 for the treatment of brain metastases (BM) in patients with HER2-positive metastatic breast cancer (BC). We retrospectively studied 12 patients treated for BM at the Institut Curie in 2014-2015 with T-DM1 and concurrent (4) or sequential (8) radiosurgery with or without whole brain irradiation. The following variables were studied: local control, clinical and radiological response as well as early and late side effects. The mean age of the population was 38 years at the time of diagnosis of BC and 46 years at of BM. All patients were with good PS. The response rate of the concurrent treatment group was 75 % with 1 complete response, 1 partial response, one stable disease and 1 progression. Comparatively, the response rate in the sequential group was as follows: two complete responses, two partial responses, six cases of stable disease and two cases of local progression. No patient experienced interruption of irradiation because of side effects. About 50 % of patients were asymptomatic after treatment. Radiation necrosis was observed in 50 % of patients in the concurrent group and 28.6 % of patients in the sequential group with a similar rate of oedema in the two groups. We found that the combination of T-DM1 and radiosurgery was feasible but can increase the incidence of radiation necrosis. Larger prospective studies with longer follow-up are needed to more clearly evaluate this association.