What factors predict the outcome of patients with HER2 positive breast cancer that has spread to the brain?

This paper studied factors that could predict outcome in patients with human epidermal growth factor receptor 2 (HER2) breast cancer that has spread to the brain. 

HER2 positive breast cancer refers to breast cancer in which there are high levels of the  protein, HER2, on cancer cells. Trasutuzumab (Herceptin) is effective in treating HER2 positive breast cancer. Lapatinib (Tyverb) is also another medication for HER2 positive breast cancer. However, patients with HER2 positive breast cancer face a high risk of brain metastasis (spread of cancer to the brain). 

432 patients with HER2 positive breast cancer that had spread to the brain were analyzed. They were followed-up for an average of 50.6 months.

The average time from diagnosis of breast cancer to brain metastasis was 35.5 months. The average survival after developing brain metastasis was 16.5 months for patients who were estrogen receptor positive (presence of estrogen receptor) and 11.5 month for patients who were estrogen receptor negative (absence of estrogen receptor). Patients with more than three brain metastases had a shorter overall survival than patients with three or fewer brain metastases. Patients treated with trastuzumab or lapatinib after developing brain metastasis had a longer survival than patients who did not receive these treatments. Furthermore, patients treated with both trastuzumab and lapatinib had a  longer survival than patients who were treated with either medication alone. Treatment with trastuzumab before developing brain metastases was not associated with length of survival after developing brain metastases.

The authors concluded that regardless of the use of trastuzumab before developing brain metastasis, treatment with both trastuzumab and lapatinib might improve survival for HER2 breast cancer patients.