“Impressive” results in breast cancer drug trial

6 minute read

A drug already approved to treat ovarian cancer has been found to improve breast cancer survival by almost a third.

An ovarian cancer drug approved in Australia for women with BRCA mutations also holds promise for treating breast cancer in women who have the mutation. New research suggests it can increase survival by almost a third. 

And Aussie researchers are now hoping the results of the global “practice-changing” clinical trial of olaparib (Lynparza, AstraZeneca) will result extend the TGA indication to breast cancer as well and secure it a PBS listing.  

Currently a 12-month course of the adjuvant therapy costs about $60,000 without subsidy. The treatment is approved and PBS-listed for ovarian cancer patients with a germline BRCA mutation. 

Details of the trial, known as OlympiA, were presented at a virtual plenary session of the European Society of Medical Oncology this month. The trial was coordinated by the Breast International Group and recruited 1836 patients worldwide, including 60 women from 12 participating institutions throughout Australia.  

The trial enrolled women with breast cancer with BRCA-1 or BRCA-2 mutations and a high risk of recurrence. At baseline, all participants were given standard treatments, including adjuvant or neoadjuvant chemotherapy. Most received a combination of anthracycline and taxane chemotherapies. 

If surgery and radiation were recommended, they also had these, as well as endocrine therapy. After that, they were randomised to receive either 12 months of twice-daily olaparib or placebo. 

The trial showed that at a median of three-and-a-half years there were 109 deaths in the placebo group and 75 deaths in the olaparib arm. 

OlympiA was led in Australia by Breast Cancer Trials Study chair and Peter MacCallum Cancer Centre medical oncologist, Professor Kelly-Anne Phillips. She said the results had exceeded her expectations and provided evidence for a “big improvement in overall survival”. 

“This is a practice-changing trial that is going to improve survival for future women who have these underlying inherited gene mutations BRCA1 or BRCA2 and who develop breast cancer,” she said. 

“Aside from the impressive survival benefit, the other important thing to note is that this was achieved with fairly minimal toxicity to the patient.  

Between the two arms there was a slight, very small difference in nausea and vomiting; a small difference in fatigue; really no difference in global quality of life between the two arms; and no difference in sort physical and emotional quality of life.” 

Professor Phillips emphasised that this was a therapy targeted specifically for women with those mutations. 

“Olaparib is an interesting drug in that it basically exploits the underlying DNA repair deficit that’s present in the cancers of women who have these germline mutations,” she said. 

“This doesn’t mean that we’ll be treating every woman with breast cancer with olaparib,” she said. “You really do have to have a mutation for this treatment to work.” 

An estimated 5% of patients diagnosed with breast cancer have an underlying inherited BRCA1 or BRCA2 gene mutation, which equates to roughly 1000 women in Australia each year diagnosed with breast cancer. Professor Phillips said this was based on Cancer Australia’s estimate that 20,030 women are diagnosed with breast cancer every year.  

“Typically, these women are diagnosed with breast cancer at a young age and may have a more aggressive form of the disease,” Professor Phillips said. 

In the US, the FDA responded quickly to the results of the trial, announcing its approval for use in patients with breast cancer who carry the gene mutations. 

Professor Phillips said she would be “very surprised” if AstraZeneca did not apply for TGA approval and PBS listing in Australia, given how “impressive” the data was. She said only a small number of patients would be able to afford to self-fund the treatment, and “not having it on the PBS would really just embed further inequities into our health system”. 

“We need to not only think about the benefits that it will have for the women with breast cancer that we’re going to be treating with these new drugs in terms of the survival benefit, which is obviously critical and remembering that these women are usually young, so they’re younger in general than your average breast cancer patient in this,” she said. 

“In this study, the median age was 42, so most of those women were very young, which fits with the inherited susceptibility to disease.” 

She said another benefit of using the drug would be an increase in the routine genetic testing, which would identify more breast cancer patients with these gene abnormalities. Currently, she said genetic testing for breast cancer patients was only funded if patients had at least a 10% chance of having an underlying BRCA one or two germline mutation, “so that misses a lot of patients”. 

“We’ll be able to offer them the drug and improve their survival but aside from that, will then be able to allow their well, healthy relatives, if they would like to, to come forward for predictive genetic testing,” Professor Phillips said. 

“And when we find these healthy people with these gene abnormalities, there are many things that we can do to prevent ovarian cancer, which is generally a deadly disease; to prevent breast cancer and/or to detect breast cancer at an early and potentially curable stage.  

“So, there’s benefits not just for the woman with the breast cancer, but potentially benefits to her family members as well.”  

AstraZeneca released a statement to Oncology Republic, saying it was “greatly encouraged” by the FDA approval, which was based on results from the OlympiA Phase III trial presented during the 2021 American Society of Clinical Oncology Annual Meeting and published in The New England Journal of Medicine. 

“We are committed to working alongside the Therapeutic Goods Administration (TGA) to ensure new treatment options that are proven safe and effective are promptly considered for registration in Australia,”the statement said. 

Professor Phillips said the latest data being presented this week would be published but there was no timeline at this stage. 

New England Journal of Medicine 2021, online 24 June 

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