Immunotherapy a new option for certain breast cancers

There have been some interesting developments in the treatment of breast cancer over the past several months.

The Food and Drug Administration (FDA) has approved immunotherapy for the treatment of metastatic triple-negative breast cancer. This is for patients whose breast cancer has spread outside of the breast and lymph nodes to other parts of the body.

The specific type of breast cancer that responds well to immunotherapy is triple-negative breast cancer, in which the estrogen receptor, the progesterone receptor and the protein HER2 are not expressed. In March, the FDA approved the drug atezolizumab (Tecentriq) in combination with nab-paclitaxel (Abraxane) for patients whose breast cancer expresses PD-L1 (programmed cell death ligand 1), which is involved in the pathway by which T-cells are able to recognize tumor cells as foreign and destroy them.

Atezolizumab is a monoclonal antibody against the protein PD-L1. In the IMpassion 130 phase III clinical trial, which was published in the New England Journal of Medicine in November 2018, there was a 2.5 month improvement in the time it took for the cancer to progress (progression free survival) and a 4.5 month improvement in overall survival.

In patients with early-stage breast cancer that overexpresses HER2, the treatment often involves receiving chemotherapy in combination with anti-HER2 antibodies trastuzumab with or without pertuzumab prior to undergoing breast surgery. This is called neoadjuvant therapy.

Prior to the results of the KATHERINE study, patients would continue on anti-HER2 antibodies after surgery and chemotherapy. After some patients received neoadjuvant chemotherapy with anti-HER2 antibodies, the cancer had disappeared at the time of surgery. This is known as a complete pathologic response.

In the KATHERINE study, patients whose cancer did not completely respond to initial treatment were randomized to T-DM1 after surgery vs. remaining on trastuzumab with or without pertuzumab. Patients who received T-DM1 had a 50 percent reduction in the risk of breast cancer recurrence compared with patients who remained on trastuzumab with or without pertuzumab.

T-DM1 has been FDA-approved to treat metastatic HER2-positive breast cancer for several years. It has a unique mechanism of action, with the antibody trastuzumab linked to a chemotherapy called emtansine. Once T-DM1 binds to the HER2 protein on a cancer cell, it is brought inside the cell and the chemotherapy is then released from the antibody and is directly toxic to the cancer cell. In this way, healthy cells in the body that do not express the HER2 protein will not be exposed to the chemotherapy and, thus, there are fewer side effects.

In addition to the two new treatments discussed above, the FDA is expected to approve other new treatments for breast cancer soon.

Breast Cancer Symposium

Who: Medical oncologist and breast cancer specialist Dr. Tiffany Svahn, with breast surgeon Monica Eigelberger and radiation oncologist Christine Chung
When: 6:30-8:30 p.m. May 22
Where: Lafayette Library, 3491 Mt. Diablo Blvd., Lafayette, CA
RSVP: or 925-677-504

Dr. Svahn is a medical oncologist and breast cancer specialist with Diablo Valley Oncology and Hematology Medical Group in Pleasant Hill. She serves as the medical director of the Women’s Cancer Center of the East Bay, where breast cancer patients meet with multiple specialists on the same day for evaluation and treatment planning. Contact her at 925-677-5041.