Case series of metastatic breast cancer patients with visceral crisis treated with CDK4/6 inhibitors.

There is an ongoing clinical dilemma of how best to treat patients who present themselves with visceral crisis. The time needed to undo the state of visceral crisis is the most relevant outcome for this patient group. We describe four patients treated with CDK4/6 inhibitor plus endocrine therapy for HR+/HER2- metastatic breast cancer who presented themselves with a visceral crisis. Two of them are male and three of them had synchronous metastatic breast cancer. Two patients had lymphangitis carcinomatosis of the lungs, one extensive disease of the eye and one of the liver. Time to first clinical response was observed within a few weeks in three patients. For one patient a switch to chemotherapy was needed. These cases show that treatment with CDK4/6 inhibitors can achieve a rapid response in patients experiencing visceral crisis. We conclude that chemotherapy is not the sole possibility in visceral crisis, and that CDK4/6 inhibitors can be considered as well.