Cancer-associated pruritus: Insights into its pathogenesis and management

Cancer-associated pruritus (CAP) is defined as pruritus attributable to an underlying malignancy or presenting as a paraneoplastic process, usually without primary skin lesions. Persistent pruritus is a common and burdensome trait of numerous neoplasms. It is most commonly seen in hematologic cancers, including Hodgkin lymphoma, polycythemia vera, and cutaneous T-cell lymphoma, as well as some solid tumors, including cholangiocarcinoma and skin cancers. Mechanistically, this chronic pruritus is largely the result of type-2 pruritogenic cytokines, in particular IL-13, IL-31, and IL-4. In many cases, these are the master messengers of pruriceptive neurons. This leads to molding immune responses through effector cells including T helper type 2 lymphocytes, mast cells, and eosinophils. Herein, we review the contemporary advances in the understanding of CAP pathophysiology, its potential molecular and cellular targets, and evolving therapies.