HER2-Directed Vaccines May Reduce Risk of Brain Metastases in Patients with HER2+ Metastatic Breast Cancer
- Sarah White
- 21 minutes ago
- 2 min read
The UW Cancer Vaccine Institute is excited to share new findings suggesting that a HER2-targeted cancer vaccine may help protect HER2-positive breast cancer patients from developing brain metastases—one of the most difficult complications to treat. Dr. Candace Haghighi presented these findings at the 2025 San Antonio Breast Cancer Symposium.
The Highlights: HER2-positive breast cancer has a high risk of spreading to the brain, where treatment options are limited. In a review of four clinical trials, patients who received a HER2-targeted vaccine developed brain metastases at lower rates than expected based on historical data. These findings suggest the vaccine may help protect against brain metastases, supporting the launch of a new Phase II trial.
HER2-positive breast cancer makes up about 15–20% of all breast cancers and is known to behave more aggressively than other types. One of the biggest challenges for people with this kind of cancer is the high chance of developing tumors in the brain. These brain metastases occur in 30–50% of patients and are very hard to treat because most cancer drugs can’t get past the brain’s natural protective barrier.
Our team has been developing vaccines that teach the immune system to recognize and attack HER2-positive cancer cells. The immune cells activated by these vaccines can travel throughout the body, including into the brain. This led us to ask an important question: could these vaccines help lower the chances of brain metastases in people with advanced HER2-positive breast cancer?
To explore this, we looked back at data from four early-phase clinical trials that included patients with stage III or IV HER2-positive breast cancer. Of the 146 patients enrolled, 12 already had brain metastases and were not included in the analysis. That left 134 patients who had all received at least one dose of a HER2-targeted vaccine.
We followed these patients for five years and reviewed their medical records to see who developed brain metastases. In total, 23 patients did, and 111 did not. When we looked at the rates of brain metastases in patients who received HER2-targeted vaccines compared to historical controls of unvaccinated patients, we found:
HER2 positive & Hormone Receptor positive patients:Â 18.9% developed brain metastases, compared to a historical rate of 22.7%
HER2 positive & Hormone Receptor negative patients:Â 14.5% developed brain metastases, compared to a historical rate of 33.6%
These differences are meaningful. Compared to historical data, this represents a 17% reduction in brain metastases for HER2+/hormone-receptor–positive patients and a 57% reduction for HER2+/hormone-receptor–negative patients.
These early findings suggest that HER2-directed vaccines may help protect against the development of brain metastases in people with advanced HER2-positive breast cancer. Based on these encouraging results, we are now designing a Phase II clinical trial to test this question more formally.
