Giving patients with a common form of breast cancer an immunotherapy drug before surgery appears to boost outcomes, a new phase 3 trial finds.

The study involved patients with estrogen receptor positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancers. That’s a tumor subtype that comprises 70% of all breast cancers, the study’s authors noted. These tumors also respond unpredictably to treatment, and can pose a high risk of spreading.

All 510 patients involved in the study had early-stage cancers, and all were good candidates for surgery. 

The immunotherapy used in the trial was nivolumab (Opdivo), a drug delivered intravenously that works by disabling a protein on the surface of cancer cells called PD-1. This helps the patient’s immune system spot and destroy cancer cells more effectively. 

The trial was funded by Opdivo’s maker, Bristol-Myers Squibb. 

The theory driving the new trial was that giving patients an immunotherapy before their tumor is removed “primes” the immune system to better recognize and destroy cancer cells. 

The international trial had about half of patients receive nivolumab before surgery, as well as standard chemotherapy. The other half received pre-op chemotherapy plus a placebo, followed by surgery. 

After their surgery, all patients also received endocrine therapy, a type of treatment targeting the tumor cell’s estrogen receptor.

Pre-op immunotherapy appeared to boost outcomes, the study authors reported.  

Looking at the percentage of patients who had a “pathological complete response” — no sign of cancer at the time of surgery — 25% of patients who got nivolumab prior to their surgery were cancer-free, compared to 14% of those who did not get pre-op nivolumab.

Patients were most likely to benefit from nivolumab if their tumors produced larger amounts of PD-1, the researchers noted.

“We hope that these results inform treatment decisions and, in turn, improve outcomes for patients with breast cancer, ultimately improving cure rates,” said study co-lead author Dr. Heather McArthur. She is professor of internal medicine in the Division of Hematology and Oncology at UT Southwestern Medical Center in Dallas.

The study was published recently in Nature Medicine.

More information

There’s more on how immunotherapy works at the National Cancer Institute.

SOURCE: UT Southwestern, news release, Feb. 4, 2025

Source: HealthDay

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