Unscheduled hydrations: redefining complete response in chemotherapy-induced nausea and vomiting studies.

Breakthrough chemotherapy-induced nausea and vomiting (CINV) is nausea and/or vomiting occurring within 5 days of chemotherapy administration despite using guideline-directed prophylactic antiemetic agents. It is highly prevalent (30-40%), usually requiring immediate treatment or "rescue" medication. If breakthrough CINV occurs, antiemetic guidelines recommend using an antiemetic agent from a different class not used in prophylaxis, along with intravenous hydration and/or dexamethasone. Data supporting these guideline recommendations are limited. Importantly, costs associated with breakthrough CINV can be substantial (i.e., unscheduled hydrations). Two retrospective analyses evaluating guideline-adherent CINV prophylaxis suggest that the initial antiemetic selection may decrease breakthrough CINV. Here we review optimal CINV prophylactic strategies and introduce unscheduled hydration as a potential important surrogate for breakthrough CINV aligning with cost-effective cancer care.