Presentations at this year?s San Antonio Breast Cancer Symposium (SABCS), being held December 5-9, 2017, discussed data from several studies that focus on Hormone Receptor positive (HR+) breast cancers.
Hormone Receptor positive breast cancers are those that have either estrogen or progesterone receptors present in or on the cancer cells. When estrogen and progesterone attach to these receptors, they lead to cancer cell growth. More than half of all breast cancer cases are HR+, and they are associated with an increased risk of late recurrence.
As we approve new drugs to treat cancer, it is important to try to improve our understanding of the efficacy and safety of these drugs in our older patients…
Cyclin-Dependant Kinase Inhibitors 4/6
Past research has shown that the use of drugs called cyclin-dependent kinase inhibitors 4/6, or CDK4/6, when used with endocrine therapy, will improve progression free survival for patients with HR+ metastatic breast cancer.?Cyclin-dependent kinase inhibitors 4/6 work by inhibiting the function of CDK4 and CDK6, which are proteins needed to drive tumor cell growth. Three CDK4/6 ihnibitors, palbociclib (Ibrance?; Pfizer), ribociclib (Kisqali?; Novartis), and abemaciclib (Verzenio?; Eli Lilly & Company) have been approved in just the last two years. 
Data presented on Friday, December 8, discussed how older women with HR+ breast cancers being treated with cyclin-dependent kinase inhibitors 4 and 6 (CDK4/6) may have similar benefits as younger women.
PFS in Older Patients
The study, conducted by the FDA, was based on data from 1,334 patients, 42% of which were 65 or older, and 24% which were 70 or older. The data showed Progression Free Survival (PFS) rates with CDK4/6 were similar in these patient groups than what is seen in younger women. For patients under 70, PFS was an estimated 23.5 months when treated with the combination of an aromatase inhibitor and a CDK4/6 inhibitor, compared to an estimated 13.8 months for patients who were only treated with the aromatase inhibitor. For the patients who were 70 or older, an estimated PFS was not reached in the group who received both CDK4/6 and aromatase inhibitors, and a PFS of 18 months was estimated for those who received only aromatase inhibitor treatment.
While previous research has shown that combining CDK4/6 inhibitors with endocrine therapy improves progression free survival in HR+ metastatic breast cancer compared to endocrine therapy alone, studies like this are significant for older patient populations who, according to researchers in this study, are underrepresented in oncology clinical trials.
?As we approve new drugs to treat cancer, it is important to try to improve our understanding of the efficacy and safety of these drugs in our older patients,? stated the study?s lead author, Harpreet Singh, MD, scientific liaison for Cancer in Older Adults and a medical officer in the Office of Hematology and Oncology Products, Center for Drug Evaluation and Research at the FDA.
Safety was also evaluated in this study. For patients who received at least one dose of a CDK4/6 inhibitor, side effects that caused discontinuation of treatment was more likely in older patients, with 20% of patients 70 or older discontinuing treatment, compared to 17% of patients 65 or older, and only 8% of patients under the age of 65. 
Lynn Howie, MD, a medical officer for the FDA and coauthor of this study mentioned that toxicity risk should be considered against potential treatment benefit, especially for older age patients.
?Health care providers should counsel each patient individually on the potential benefit of these therapies as well as the potential risks, taking into account the patient?s disease characteristics, performance status, comorbidities, social support, and treatment preferences,? Howie stated.
Another study presented on Friday dealt with the possibility of predicting late recurrence by monitoring circulating tumor cells in HR+ breast cancer patients.
Last Editorial Review: December 8, 2017
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