Palbociclib and Letrozole: New Hope for Breast Cancer Patients with Residual Disease

In the fight against breast cancer, doctors are constantly searching for better ways to treat the disease. One recent study, known as the PROMETEO II trial, looked into combining two drugs - palbociclib and letrozole - to help patients with a specific type of breast cancer. This type of cancer is hormone receptor-positive and HER2-negative, and it often leaves behind some cancer cells even after initial chemotherapy. The goal of the PROMETEO II trial was to see if these two drugs could stop the cancer cells from growing and to find out which patients would benefit the most from this treatment. The study found that about 60% of patients had a complete stop in cell growth, as measured by a protein called Ki67. This was a significant improvement from the chemotherapy alone. The study also found that the treatment changed the type of cancer cells in some patients and increased the activity of certain immune system genes. However, about 14% of patients had a side effect called PD-L1, which can make some immune system treatments less effective. Nine patients also had more serious side effects. Overall, the study shows promise for using palbociclib and letrozole to treat this type of breast cancer, but more research is needed to understand who will benefit the most and how to manage the side effects.