Howard A. "Skip" Burris, III, MD, chief medical officer and executive director, Drug Development Program, Sarah Cannon Research Institute in Nashville, Tennessee, discusses the need for patient population stratification in breast cancer trials.

HER2-positive breast cancer has a tendency to grow very rapidly with each case presenting similar growth characteristics, whereas hormone-receptor sensitive, or ER-positive, breast cancer comes in many different shapes and sizes. Some types of ER-positive breast cancers grow very rapidly and others contain bone complications or visceral metastases. These populations represent unique disease types and each reacts to treatment differently.

In the case of mTOR inhibitors, Burris explains that a retrospective analysis of the original first-line temsirolimus (Torisel) phase III trial shows that it contained a very heterogeneous group of patients.

The stratification of a patient population creates a more homogenous group, which provides a more exact patient profile and aids the discovery of the most beneficial treatment. Burris believes it is best to stratify ER-positive patients into various groups, since the disease has a tendency to be very heterogeneous.