Targeted therapies improve overall outcomes of patients with rare breast cancer subtypes and, in some cases, improve pathologic complete response rates (pCR) and overall survival to rates comparable to those of patients with breast cancer of no special type.

Alexandra Thomas, MD, medical oncologist with the Duke Cancer Institute (DCI) breast oncology program, presented these results from the I-SPY2 trial at ASCO Breakthrough: A Global Summit for Oncology Innovators.

Thomas and her team were able to retrospectively determine the tumor molecular signature and receptor status to classify the response predictive subtype (RPS).

Based on the tumor’s RPS, Thomas said they were able to retrospectively review outcomes for patients with tumors that had received therapies directed at disease RPS vulnerabilities. These include therapies such as immune checkpoint blockades, which harness a patient’s immune system to help fight cancer. For example, patients identified with HER2-positive breast cancer who received HER2-directed therapy had a higher pCR, indicating no tumor at the time of surgery after upfront cancer treatment.

“We found that if you can find the tumor’s Achilles’ heel and attack it, outcomes for these patients are the same as patients with more common tumor types,” Thomas said.

Thomas’ study was also one of the largest cohorts to show that pCR rates for patients with rare tumors more closely match rates in patients with more common subtypes. This information could empower providers to more readily consider targeted therapies for these patients.

Currently, Thomas is looking into potential cross-disciplinary research opportunities to see if results gained from this research could support targeted therapy interventions in patients with other cancers. The ISPY-2 trial is also looking into pharmacological interventions like antibody-drug conjugates to further support breast cancer patients.

“This research proves that we, as medical providers, can get these tumors treated,” Thomas said. “The more we can focus on a personalized medical approach for these patients, the better their overall outcomes will be.”