Hyponatraemia and cancer.

Hyponatraemia is the most common electrolyte alteration in cancer patients and the main cause is the syndrome of inappropriate antidiuresis. In this context, arginine vasopressin secretion can be due to ectopic secretion by tumoral cells or to drugs, including chemotherapeutics. It is known that hyponatraemia is associated with a worse prognosis in cancer. Conversely, the correction of serum [Na+] is associated with a favourable effect on the disease's outcome. Basic research provided evidence that reduced [Na+] activates several intracellular pathways in cancer cells, which lead to an increased growth and invasiveness. Interestingly, vasopressin receptor antagonists, mainly used for the treatment of hyponatraemia secondary to the syndrome of inappropriate antidiuresis and in polycystic kidney disease, effectively reduced cancer cell proliferation in in vitro and in vivo experiments. Although this needs to be confirmed on clinical grounds, it is tempting to hypothesize that vasopressin receptor antagonists might have a possible role in future anti-cancer strategies.