Metastatic triple-positive breast cancer frequently resists treatments. Scientists at the University of Colorado Cancer Center are testing a unique combination of medications to change that.
Growth of breast cancer cells is often propelled by one of three receptors – estrogen receptors (ER), progesterone receptors (PR) or the growth factor receptor called HER2. Treatments exist targeting each of these receptors individually. However, when all three receptors are present – this “triple-positive” breast cancer – blocking any single receptor is not enough. Treatments that block hormonal (estrogen and progesterone) receptors may be not very effective because tumor cells may use HER2 receptor to grow. The drugs that block HER2 receptors may not work as well because the cells will use hormonal receptors to survive. Chemotherapy works against triple-positive breast cancers, however, it has multiple side effects. Previous clinical trials have been largely unsuccessful in defining a well-tolerated targeted drug combination that blocks all avenues for growth of triple-positive breast tumors.
“Under the current guidelines, patients with triple-positive metastatic breast cancer have two options as a first line of treatment and neither is a great option,” says Elena Shagisultanova, MD, PhD, investigator at the CU Cancer Center and assistant professor in the University of Colorado School of Medicine’s Division of Medical Oncology. “One approach is to start an anti-hormonal pill, which is generally non-toxic. However, the response usually lasts only three to four months. The other choice is to start chemotherapy combined with HER-2 targeted agents. This option is effective, but it has multiple side effects.”