Results from the DIAmOND clinical trial have shown that adding dual immunotherapy to existing treatments could be promising for selected women and men with advanced HER2-positive breast cancer.
The DIAmOND study was developed by Australian researchers and is a world-first clinical investigation into whether giving patients dual immunotherapy, in combination with the drug Trastuzumab (commonly known as Herceptin), can prolong the duration of cancer control in patients with advanced HER2-positive breast cancer that has become resistant to Trastuzumab.
Immunotherapy drugs like Durvalumab and Tremelimumab, as used in this study, assist the body’s natural immune system to attack cancer cells.
The combination of these two drugs has been given previously to people with lung cancer, but this is the first clinical trial that has tested the combination of these two drugs in people with breast cancer.
IS TISSUE THE ISSUE?
Researchers have found that:
- Among the 68 trial participants, the new treatment combination showed an overall response rate of 27% in those with oestrogen receptor-positive cancer.
- Patients whose cancer was estrogen receptor (ER)-positive and had high levels of tumor-infiltrating lymphocytes (TILs) exhibited significantly better outcomes, with an overall response rate of 63%.
- Cohort 3 of the trial utilised a single priming dose of Tremelimumab, followed by Durvalumab and Trastuzumab. This approach resulted in 27% of patients alive and with their cancer under control at 12 months (progression-free survival, PFS), surpassing the 13% PFS observed in the PANACEA trial. Additionally, this strategy was associated with a favorable safety profile, including fewer treatment discontinuations and reduced incidence of severe toxicities.
- Some patients experienced durable cancer control lasting up to 30 months, indicating the potential long-term benefits of this treatment combination.
Professor Sherene Loi developed and led the DIAmOND clinical trial and presented the results at the ESMO Breast Cancer Congress 2025. The trial was conducted by Breast Cancer Trials, Australia’s largest Independent Oncology Clinical Trials Research Group.
“These promising results suggest combining new immunotherapy treatments with Trastuzumab may offer a new treatment option for patients with treatment-resistant HER2-positive breast cancer,” Professor Loi explained.
“These findings provide a compelling case for further exploration and how we can best integrate this treatment combination into clinical practice.”
Since 1978, Breast Cancer Trials has conducted a multicentre national and international clinical trials research program into the treatment and prevention of breast cancer. More than 980 researchers in 118 institutions across Australia and New Zealand are committed to our vision of no more lives cut short.
Source: BCT
