Fresh hope emerges for patients with rare forms of breast cancer

A groundbreaking new treatment has shown remarkable promise in significantly reducing the risk of disease progression or death in patients with a less common type of breast cancer one that has seen little advancement in treatment options for more than ten years.

The findings, unveiled Monday at the American Society for Clinical Oncology's annual conference, are expected to be submitted for regulatory approval. If approved, the treatment could soon become the go-to

Patients diagnosed with HER2-positive metastatic breast cancer a form that has spread beyond the breast typically have a life expectancy of around five years.

Dr. Sara Tolaney, head of the breast oncology division at Dana-Farber Cancer Institute, described the study’s results as remarkable. "We were genuinely impressed by the dramatic improvement we're essentially doubling the time patients can keep their cancer in check compared to the current standard," she told AFP.

Currently, the standard treatment referred to as THP combines chemotherapy with two targeted antibodies that block the HER2 protein’s growth signals.

The new strategy involves a drug called trastuzumab deruxtecan (T-DXd), which links an antibody to a chemotherapy agent, delivering a more targeted and potent attack on cancer cells.

This innovative "smart bomb" approach enables the drug to deliver chemotherapy directly into cancer cells. “It binds to the cancer cell and releases the chemotherapy payload right inside,” explained Dr. Sara Tolaney. “That targeted delivery is what earns it the nickname ‘smart bomb’ and likely why we're seeing such a boost in effectiveness.”

While common side effects included nausea, diarrhea, and reduced white blood cell counts, a rarer but more serious risk was lung scarring.

T-DXd is already approved as a second-line treatment used after initial therapies fail. But this latest trial explored its use as a first-line option, paired with another antibody, pertuzumab, to potentially amplify its benefits.

In the international study led by Tolaney, nearly 400 participants were randomly selected to receive the T-DXd and pertuzumab combination.

Another group received the current standard treatment, known as THP. A third set of patients was given T-DXd alone, though those results have not yet been made public.

After two and a half years of follow-up, the combination of T-DXd and pertuzumab reduced the risk of disease progression or death by 44% compared to the current standard treatment.

Notably, 15% of patients receiving the new therapy experienced complete remission, where no signs of cancer were detectable, compared to 8.5% in the standard THP group.

Although this analysis was conducted partway through the study, early findings show the median progression-free survival the point at which half of the patients saw their cancer return or worsen, reached 40.7 months with the new combination, significantly higher than the 26.9 months seen with standard care. That number may increase further as the study continues.

Dr. Tolaney confirmed that the data will be submitted to health authorities globally, including the U.S. Food and Drug Administration. Future research will focus on determining how long patients, especially those in full remission,n should stay on the drug.

Dr. Rebecca Dent, a breast cancer expert at the National Cancer Center Singapore who was not involved in the study, called the results a game changer: "This marks a new standard of care for first-line treatment of HER2-positive metastatic breast cancer."