 This study investigated the effectiveness of CDK4-6 inhibitors combined with endocrine therapy, ET, as a treatment option for patients with hormone receptor positive human epidermal greif factor receptor 2 negative metastatic breast cancer, HR+, H2, who have progressed after initial chemotherapy. Researchers analyzed tissue samples from 89 patients before and during treatment to determine the genetic and molecular changes that occur when the tumours become resistant to the drugs. They found that certain genes and mutations are associated with poor prognosis and can lead to resistance to the drugs. Additionally, they discovered that some tumours switch to more aggressive subtypes with estrogen independent characteristics. This research provides valuable insight into how to better treat these types of tumours and may help to develop new strategies to combat drug resistance. This article was authored by Yanhee Park, Siokarim, Yanhee Park, and others. We are article.tv, links in the description below.