Understanding risk of recurrence in hormone positive breast cancer is really important to make sure patients have the most appropriate treatment to prevent their cancer coming back. So we know that endocrine therapy can prevent cancer coming back but, despite that, patients can have considerable residual risk. So we’ve looked for many years to try and improve outcomes. CDK4/6 inhibitors already work in metastatic disease so we’ve run trials now in early breast cancer to see if adding them can improve outcomes.

I’ve been the global PI for the monarchE trial which recruited patients with really quite high risk of recurrence. That was four or more involved lymph nodes or if they had 1-3 lymph nodes, either a large tumour or a grade 3 cancer. So the trial started nearly eight years ago and we gave patients who completed all their standard treatment – surgery, chemotherapy, which was in 95% of patients – either endocrine therapy alone for up to 10 years or endocrine therapy plus two years of the CDK inhibitor abemaciclib.

The first results came out around about five years ago showing that it reduces the recurrence rates of cancer and we’ve followed the trial for a number of years since.  The drug became approved in many countries based on that fact alone but the question remained – will it improve overall survival?

The new data that was presented at ESMO today now shows the benefit of preventing cancer from coming back and curing potentially more patients. So this was an analysis dependent on reaching a certain number of deaths in the study and then analysing to see if there was a significant reduction. The answer is yes, we have a 15.8% reduction in risk of death and that represents a really significant improvement. The absolute improvement at seven years is just under 2%. So this means that patients not only are preventing having their cancer coming back but that means more patients are living now. The primary reason that they’re living is that they’re not getting metastatic disease. So if their cancer doesn’t return and they don’t develop metastases, and we’ve shown that 30% fewer patients will get metastatic disease, in years to come that means that the actual survival of patients is actually improved.

The real significance of this is this is the first time in over 20 years that a new treatment has come in in this subgroup of ER+ breast cancers to improve overall survival. So it represents a real milestone in the development of treatments for this form of common breast cancer.

Is there anything else you would like to add?

The real implications of these findings for clinicians is that they can talk to patients with confidence about the fact that the treatment not only delays the recurrence of cancer, it delays the development of metastatic disease and, as a consequence, more patients are actually alive because of it.

The treatment does have some additional short-term side effects so it is important for clinicians to understand that. If patients are deemed to be high enough risk for the therapy, then it is a price we feel it is worth paying to not only prevent cancer returning but now actually improve the survival of those groups of patients.