PracticeUpdate: Haematology & Oncology

AMERICAN SOCIETY OF CLINICAL ONCOLOGY 2016 ANNUAL MEETING 14

Dr Reshma Mahtani discusses key breast cancer trials at ASCO 2016

Extending endocrine therapy The MA.17R study 1 looked at patients who had received 5 years of an aromatase inhibitor, either up front for 5 years or after 2 to 3 years of tamoxifen. These patients were randomised to an additional 5 years of an aromatase inhibitor (letrozole) versus placebo. At 5 years of follow up, 95% of women receiving letrozole and 91% of those receiving placebo were breast cancer-free. The 34% lower risk of recurrence associated with continuation of letrozole is clinically meaningful. However, the take-away point is that over 90% of patients in both arms were disease-free, which highlights the fact that patients this far out from a breast cancer diagnosis are doing quite well. These small incremental gains that we’re making really have to be balanced against the side effects and toxicities of the therapy. Patient overall quality of life was comparable between the two groups; however, this analysis is, of course, selected for those patients who were able to tolerate the first 5 years of therapy, and doesn’t take into account all those patients who came off therapy earlier on for quality-of-life issues. Efficacy of adding a CDK4/6 inhibitor to endocrine therapy For patients with metastatic ER-positive/HER2-negative breast cancer, the PALOMA-2 trial 2 confirmed the results of PALOMA-1 by demonstrating that the addition of the CDK4/6 inhibitor palbociclib to letrozole in the first-line setting was associated with a significant improvement in progression-free survival (PFS). The important finding was a 10-month difference in PFS. It didn’t quite meet the doubling in PFS of 10 to 20 months that we saw in PALOMA-1; however, 14.5 to 25 months is still quite remarkable and is, of course, clinically meaningful. Aside from the efficacy data, the psychological impact of being able to tell a patient that she is doing well on her anticancer

Reshma L. Mahtani DO, is Assistant Professor of Clinical Medicine at the Sylvester Comprehensive Cancer Center at the University of Miami.

therapy should not be minimised. Finally, there were no new safety signals, the drug is very well-tolerated, and the results confirm the efficacy noted in the first-line setting in the earlier phase 2 study. A biomarker that’s prognostic, but also predictive of endocrine therapy benefit Endocrine therapy is not without toxicities, and, if we look across the board at all of the extended endocrine studies, we’ll notice that the absolute magnitude of benefit is about 3% to 5% with the addition of extended endocrine therapy. This really highlights the need to have a biomarker to identify which patients will benefit. Not only do we need a biomarker that’s prognostic, but one that is also predictive of endocrine therapy benefit. There are several diagnostic assays that are looking at this. In my opinion, the Breast Cancer Index is the one that has gone the farthest in having data in both

the prognostic and predictive areas. Assessing the right assay for molecular profiling

The important thing to establish initially is that we know clinicopathologic factors alone, such as tumour size and nodal status, are not useful to use in isolation to determine risk of late recurrence. Although there is a carry-over

© ASCO/Rodney White 2016

PRACTICEUPDATE HAEMATOLOGY & ONCOLOGY