Precision drug combo boosts survival in younger women with advanced breast cancer

Combining a targeted drug with hormone therapy extended the lives of pre-menopausal women with advanced breast cancer in a clinical trial.

US researchers at UCLA found adding ribociclib (Kisqali) to standard hormone treatment improved survival by 24%.

After three and a half years follow up, 70 in 100 women who received the combination treatment were still alive. This was compared with 46 in 100 of those who took the standard hormone treatment with a dummy drug (placebo).

The results will be presented at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago and published in the New England Journal of Medicine.

Dr Jason Carroll, a breast cancer expert at the Cancer Research UK Cambridge Institute, said the results were the “first time” that overall survival improvements had been seen with this drug combo. 

Tackling advanced breast cancer

Although less common than in older women, advanced breast cancer rates in pre-menopausal women are increasing, said ASCO. The disease can be very aggressive in younger women.

Hormone therapy, which blocks the effect the sex hormone oestrogen has on breast cancer cells, is prescribed as a treatment for those living with breast cancer that is fuelled by this hormone.

Ribociclib is a drug that switches off two important molecules called CDK 4 and 6 that can fuel the rapid growth of cancer cells. The clinical trial, called MONALEESA-7, looked at the impact of combining hormone treatment with the precision drug.

‘A first’ for targeted drug

Patients’ breast cancers were tested and those that carried hormone-sensing molecules but didn’t have the molecule HER2 were eligible for the study. 672 women met these criteria and were randomly treated with either ribociclib or placebo, alongside hormone therapy.

A quarter of women taking the targeted drug and hormone therapy died during the study. This compared to a third of women taking the placebo with standard hormone treatment.

Based on a follow-up time of three and half years, this represented a 29% reduction in risk of death thanks to ribociclib.

Carroll said the increased survival with the targeted drug was a first.

“Ongoing work will determine whether these drugs could also impact overall survival in women who have already gone through the menopause and these trials are currently running,” he added.

More research needed

Dr Sara A. Hurvitz, director of the Breast Cancer Clinical Research Program at UCLA and who led the study, said: “This is the first study to show improved survival for any targeted therapy when used with endocrine [hormone] therapy as a first-line treatment for advanced breast cancer.”

Carroll called the study an “excellent example” of how a better understanding of cancer biology can impact patients’ lives. 

“It is also important to identify specific groups of women most likely to benefit, sparing others from unnecessary additional treatment and any related side effects,” he said.

The researchers say they will now need to analyse the results further. They plan to look at how patients say the treatments were for them, as well as studying blood samples to hunt for signs that might help identify those most likely to benefit from the treatment.

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Where did these results come from?

The ASCO annual meeting is the largest gathering of clinical cancer experts in the world.

Researchers share preliminary and more advanced results. These come from small, early stage studies through to large randomised clinical trials.

In some cases, the results will go on to change how patients are treated. But most of the results are yet to be published in a scientific journal, so only offer an early glimpse of what these trials may later confirm.