Immunotherapy plus standard therapy can increase progression-free survival in patients with HER2+ metastatic breast cancer, trial suggests

Adding an immunotherapy agent to the standard therapy for HER2+ metastatic breast cancer can significantly extend the time in which the disease is held in check, according to new research led by Ada Waks, MD, a breast oncologist at Dana-Farber Cancer Institute.

A phase II trial, dubbed AVIATOR and presented today by Waks at the San Antonio Breast Cancer Symposium, compared three treatment regimens in 100 patients previously treated for metastatic HER2+ breast cancer: standard therapy (chemotherapy plus the HER2-targeting drug trastuzumab); standard therapy plus avelumab (an immune checkpoint inhibitor, which lowers tumor cell defenses against a T-cell attack); or standard therapy plus avelumab and utomilumab (an immune cell-stimulating drug). All participants had previously been treated for the disease, with 63% receiving more than three lines of prior treatment.

At a median follow-up of six months, 31.2% of the patients treated with standard therapy plus avelumab were alive with no worsening of their disease, compared to 18.8% of those receiving standard therapy alone, researchers found. The addition of utomilumab provided no additional benefit.

Overall, 20% of patients in the standard therapy-plus-avelumab group responded to the therapy – with at least a partial reduction in their cancer – compared to 11.1% in the standard therapy group and 11.8% in the standard therapy-aveluamb-utomilumab group.

The percent of patients experiencing treatment-related adverse side effects was similar in all three groups. Only three patients left the trial because of unacceptable side effects.

"The AVIATOR trial provides the first positive results for combining an immune checkpoint blockade with chemotherapy plus trastuzumab," said Waks. "Though this was a relatively small phase II trial, we are excited about the promise of these results and look forward to additional future data investigating the benefit of immunotherapy in pre-treated HER2+ metastatic breast cancer."