Longitudinal monitoring of cerebrospinal fluid-derived circulating tumor cells: a pilot study

Breast cancer-associated leptomeningeal metastasis (LM) is a particularly aggressive syndrome with an abysmal prognosis. Here we applied the SE-i•FISH platform for surveillance and function analysis of cerebrospinal fluid-derived circulating tumor cells (CSFTCs) from five breast cancer patients with LM. We observed a negative correlation of CK18 expression on CSFTCs with clinical symptom remission, and confirmed that at least six intrathecal chemotherapies were necessary. We also present the case of a breast cancer patient with bladder and leptomeningeal metastasis. The bladder is an extremely unusual site for metastasis from primary breast cancer, with only 14 cases sporadically reported worldwide. Our platform could help monitor CSFTC numbers and treatment responses for patients with LM.