Guiding Treatment With Molecular Testing in Breast Cancer

There are many types of breast cancer, with hormone receptor-positive, HER2-positive, and triple-negative representing the 3 mains subtypes, notes Ingrid A. Mayer, MD, MSCI. Each breast cancer subtype possesses its own molecular features and drivers, states Ian E. Krop, MD, PhD. The knowledge that each of these drivers may be vulnerable to a specific drug has contributed to a lot of the progress seen in breast cancer treatment.

Estrogen-receptor (ER)—positive disease can be managed with estrogen blockers and tends to have a fairly good prognosis, says Mayer, and many individuals perform well with endocrine therapy alone. HER2-positive breast cancer is an aggressive disease, but targeted therapies against HER2 have helped individuals live for many years with a great quality of life, comments Mayer. Triple-negative disease remains an aggressive disease for which chemotherapy is the current best option. Recurrences occur quickly, says Mayer, and unfortunately patients do not live long once their disease recurs. The challenge is identifying the target driving triple-negative disease, adds Krop.

Commercially available genetic tests allow clinicians to examine a patient’s somatic mutations, explains Krop. The recurrent score or Oncotype DX assesses patients with early stage (stage 1 or 2) ER-positive breast cancer to determine if they require chemotherapy or may respond well to endocrine therapy by itself. The platform helps guide decisions in whether an individual needs more aggressive treatment, says Mayer.