A new study has reported that breast cancer patients with a change in HER2 status between their primary tumor and a recurrence have a worse prognosis than patients who remain HER2 positive. Up to 25 percent of breast cancers overexpress the HER2/neu gene. This gene has a role in the pathways leading to cell growth and differentiation, which accounts for the reputation of aggressiveness of this type of breast cancer.

The study included 151 breast cancer patients with recurrences whose primary tumors were analyzed for HER2 status. The sites of recurrence were bone/bone marrow (30%), liver (16%), local recurrence (18%), lung/pleura (10%), axillary lymph nodes (9%), nonlocal skin (7%), supraclavicular lymph nodes (5%), and other sites (7%). Locoregional (in the breast, chest wall, or lymph nodes) and distant recurrences were investigated using aspiration cytology.

HER2 status was found to differ between the primary breast cancer and a recurrence in 15 patients, or 10% of the study group (discordance). In seven of 108 women, HER2 status changed from HER2 negative in the primary to HER2 overexpressing in a recurrence. In eight of 43 women, the status changed from HER2 positive to HER2 negative. Women with discordant HER2 status between the primary tumor and a recurrence were found to have more than five times the risk of dying compared to patients with stable positive HER2 status. The authors conclude that unstable status for HER2 in breast cancer is clinically important and should motivate more frequent testing of recurrences.