IMMUNOTHERAPY SHOWS PROMISING RESULTS

The PANACEA clinical trial has shown promising early results for women with advanced HER2-positive breast cancer, who are resistant to treatment with trastuzumab.

PANACEA is a phase I/II clinical trial and the first study to test the combination of the drugs pembrolizumab (Keytruda) and trastuzumab, to find out the most suitable dose when these drugs are used together and to assess if their combined use is an effective treatment.

The study found that the combination treatment was well tolerated in patients and had clinical benefit in patients whose tumours were positive for a biomarker for pembrolizumab.

The results were announced at the San Antonio Breast Cancer Symposium in the United States. The trial was sponsored and managed by the International Breast Cancer Study Group and coordinated in Australia by Breast Cancer Trials. 58 patients were enrolled in the study worldwide including 21 from Australia. The International Study Chair is Associate Professor Sherene Loi.

It is estimated that approximately 20% of invasive breast cancers are HER2-positive, and some of these patients develop resistance to trastuzumab, a HER2-specific monoclonal antibody utilised for treatment of the disease. The standard treatment for HER2-positive breast cancer that has progressed is to continue treatment with trastuzumab and to add another type of therapy of chemotherapy.

It is thought that cancer cells with increased levels of the protein called PD-1, avoid detection by the body’s natural immune system. Prior research has shown that patients with trastuzumab-resistant advanced HER2-positive breast cancer have evidence of poor immune responses and preclinical studies revealed that anti-PD1 immunotherapy may help to overcome this resistance in this subset of breast cancers. Pembrolizumab and trastuzumab have been given together to see if they can decrease the level of PD-1 in breast cancer and allow the body’s immune system to identify and work against the cancer cells.

“This proof of principle study suggests that immune evasion is a mechanism of resistance to trastuzumab and contributes to disease progression in advanced HER2-positive breast cancer,” said Associate Professor Sherene Loi.

“These are positive initial results and further research is now needed which we hope will lead to a new treatment option for women diagnosed with advanced HER2-positive breast cancer.”

Breast Cancer Trials is the largest, independent, oncology clinical trials research group in Australia and New Zealand. For almost 40 years, Breast Cancer Trials has conducted a national clinical trials research program for the treatment, prevention and cure of breast cancer. For more information about Breast Cancer Trials, visit www.breastcancertrials.org.au.

Associate Professor Sherene Loi is supported by the current Cancer Council Victoria John Colebatch Fellowship.

Media contact: Anna Fitzgerald, Breast Cancer Trials Communications Manager Phone: 02 4925 5255 or 0400 304 224; Email: anna.fitzgerald@bctrials.org.au