Comment: The use of CDK 4/6 inhibitors now translates to a significant survival benefit in breast cancer treatment

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Published: 1 Jun 2019
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Dr Harold Burstein - Dana-Farber Cancer Institute, Boston, USA

Dr Harold Burstein comments on data, during a press conference at the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting, from the MONALEESA-7 trial.

This was a phase III randomised trial in which pre-menopausal women with advanced breast cancer received ribociclib on top of the standard of care endocrine therapy.

Watch Dr Hurvitz's press conference here, and interview here.

Dr Richard Schilsky

I’d like to turn to Dr Hal Burstein for a few additional remarks.

Dr Harold Burstein - Dana-Farber Cancer Institute, Boston, USA

Thank you and good morning. It’s really exciting to be here this morning because the golden age of clinical research in oncology continues and the theme we see in this presentation, and I think the one to follow in lung cancer, is that with mature and robust data we are now seeing substantial improvements in survival with the innovative drugs that are coming to our market.

This is an important study because it shows that a class of drugs, CDK4/6 inhibitors, which we are widely using and have been shown to delay the time to treatment progression, delay the time to the need for chemotherapy for advanced breast cancer and really double the effectiveness of endocrine therapy, now also translates into a significant survival benefit for women who have ER positive metastatic breast cancer.

It’s also significant because, as Dr Hurvitz mentioned, this study focusses on a group of young women and young women, while many people think of them as having different kinds of breast cancer like triple negative breast cancer or HER2 positive breast cancer, in fact the most common form of breast cancer in young women is oestrogen receptor positive breast cancer and this is the largest study in recent memory that has focussed exclusively on premenopausal women and shows that they too benefit from this class of drugs in a remarkable way.

Finally, in an era when we are thinking about value in oncology care, the demonstration of a robust survival difference substantially adds to a value proposition for products like ribociclib that were discussed here. So hopefully these data will enable access to this product to more women around the world, particularly in healthcare systems which assess value rigorously as part of their decisions for national access to drugs.

So, important survival data in a group of patients historically understudied, now shown to have a benefit and clearly established the value of this class of drugs in the management of the most common form of breast cancer.

Dr Richard Schilsky
Hal, if I could just ask you one follow-up question. As you mentioned, this is a class of drugs, there are several other CDK4/6 inhibitors that are approved for the treatment of breast cancer. Could you just comment us to are the other drugs also used in premenopausal women and have the other drugs reported out any survival data?

Dr Harold Burstein

There are three commercially available products – ribociclib, palbociclib and abemaciclib – marketed in the US. They’ve all been approved, as Dr Hurvitz said, through very similar trials principally looking at postmenopausal women. This trial was the only study that exclusively looked at premenopausal women. There have been some premenopausal women included in subsets of the other trials and an FDA analysis done last year showed that very similar trends in terms of progression free survival for younger or older women.

One of the myths that this study helps suppress is the idea that young women with ER positive breast cancer have a fundamentally different outcome than older women. Actually their outcomes look very similar. As Sarah mentioned, this is the first study that has shown a statistically significant survival benefit, maturation of other studies continues. There was a report last fall for a different product, palbociclib, that was in postmenopausal women. Again, a longer follow-up – the curves began to separate but the p-value was 0.08 so it was not quite statistically significant. I think that in the breast cancer community these data on top of that earlier finding are really making people think that as a class of drugs there’s a real survival signal here and we have embraced and will continue to embrace the class of drugs for that reason.

Dr Richard Schilsky

Are there any significant differences in side effect profile among the three commercially available drugs?

Dr Harold Burstein

By oncology standards these are all very well tolerated drugs, they are oral medicines, they are portable – patients can take them in their communities and they can travel with them and it’s a relatively easy medicine. They do cause occasional problems with low white blood counts or lower GI symptoms like diarrhoea and the different products have very subtle differences in their overall tolerability. But, again, for the most part they are considered quite well tolerated products.