Australian researchers nearly double cure rates for the most common breast cancer

Researchers in Australia have found that adding a single immunotherapy drug to standard pre-surgery chemotherapy nearly doubled breast cancer cure rates in patients with the most common form of the disease. The Phase III CheckMate-7FL trial, led by Professor Sherene Loi of the Peter MacCallum Cancer Centre in Melbourne and the University of Melbourne, enrolled 510 patients and produced results the research team called a new treatment paradigm. The findings were published in Nature Medicine on Jan. 21, 2025.

• The trial targeted estrogen receptor-positive, HER2-negative breast cancer — the most common subtype, accounting for around 70% of all breast cancer cases globally — a group that has historically shown low response rates to chemotherapy alone.
• Adding nivolumab, an immunotherapy drug already approved for other cancers, to pre-surgery chemotherapy raised pathological complete response rates from 13.8% to 24.5% — nearly double — across all trial participants.
• In patients whose tumors carried the PD-L1 biomarker, the improvement was even sharper: response rates rose from 20.2% to 44.3%, representing what researchers called unprecedented results in this breast cancer subtype.

Pathological complete response — or pCR — means that when surgeons removed the tumor, they found no detectable cancer cells in either the breast tissue or the lymph nodes. “These patients are considered to be likely cured,” Professor Loi said, “because their tumor was removed and samples of breast and lymph node tissue collected at the same time also show no detectable cancer cells.” Long-term event-free survival data is not yet available, but pCR is an established surrogate marker for improved outcomes in breast cancer research.

Why improved breast cancer cure rates in this subtype matter

The ER-positive, HER2-negative subtype is the breast cancer most women get. It accounts for roughly 7 in 10 diagnoses worldwide, and improving outcomes for that group affects more patients than breakthroughs in rarer subtypes. It has also long been considered unlikely to respond to immunotherapy — a view rooted in biology, since this subtype generally has fewer immune cells infiltrating the tumor than triple-negative breast cancer, which has driven most of the immunotherapy excitement in recent years.

The CheckMate-7FL trial challenged that assumption by specifically enrolling patients with high-risk, high-grade tumors — a subgroup known to have more immune activity. Nivolumab works by blocking the PD-1 receptor on the immune system’s T cells. Normally, when PD-1 binds to proteins found on some cancer cells, it instructs T cells not to attack. Nivolumab prevents that signal, effectively unmasking the cancer so the immune system can attack it. In patients whose tumors already showed immune infiltration, the drug’s effect was dramatic.

The results were confirmed by a parallel trial, KEYNOTE-756, which used a different immunotherapy drug — pembrolizumab — and found nearly identical improvements in pCR rates. Two independent Phase III trials reaching the same conclusion in the same subtype, published months apart, is a meaningful signal in oncology research. Professor Loi and colleagues concluded that the results represent “a new milestone in the neoadjuvant treatment of ER+/HER2– breast cancer, because there have been intensive but thus far unsuccessful efforts to improve pCR rates in this patient population.”

What comes next for breast cancer cure rates research

The immediate next step is long-term follow-up. Oncologists want to see whether the improved pCR rates translate into reduced recurrence and better survival at five and ten years. That data will take time. Researchers and clinicians have noted that neoadjuvant immune checkpoint therapy should not yet be offered outside a trial setting until recurrence data matures — a caution the Peter Mac team acknowledges directly in the published findings.

There were also safety findings that warrant attention. Five patients in the nivolumab group died during the trial, two from drug-related toxicity. No deaths occurred in the placebo group. The overall rate of serious adverse events was higher in the nivolumab arm. Those risks will need to be weighed against the benefit as the treatment moves toward potential clinical adoption. Peter Mac’s announcement of the trial results emphasized that the research team is continuing to investigate which patients are most likely to respond — with the PD-L1 biomarker emerging as the strongest predictor — to ensure the drug reaches those who will benefit while sparing others from unnecessary exposure.

What is already clear is that a door has opened. Researchers now have Phase III evidence that immunotherapy can work in a breast cancer subtype where it was previously assumed not to — and that the key is identifying the right patients through biomarker testing before treatment begins. The next generation of trials will be designed around that principle.

This result is part of a broader documented pattern of cancer progress. U.K. cancer death rates recently fell to their lowest level on record, down 29% from their 1989 peak. India has treated more than 6.8 million cancer patients for free in the past seven years. The science and the systems around it are both improving. More good news in global health is being made every week — most of it going unreported.

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This story was originally reported by New Atlas.