Prochlorperazine and 5HT3 antagonists for the treatment of breakthrough chemotherapy-induced nausea and vomiting occurring despite prophylactic antiemetic therapy.

e19590 Background: Chemotherapy-induced nausea and vomiting (CINV) is one of the most debilitating side effects of cancer therapy. Previous studies have primarily focused on prophylactic therapy, which have reduced the incidence of CINV to 15-40%, but no previous studies have been performed to evaluate treatment of breakthrough CINV. Methods: A prospective, observational pilot study was performed to evaluate the efficacy of individual agents prescribed for the treatment of CINV that occurred despite the use of prophylactic agents. Enrolled patients (pts) were receiving moderately or highly emetogenic chemotherapy and prophylactic treatment of CINV consistent with current NCCN, ASCO, or MASCC guidelines and were prescribed an antiemetic for breakthrough CINV. If pts had nausea, that occurred within the first 3 days of chemotherapy administration and that required their anti-emetic medication, they were instructed to complete a questionnaire every 30 minutes for 4 hours with the start of anti-emetic medication. Levels of nausea (0-10), vomiting and side effects were self recorded by the patients. Results: Of the 96 pts enrolled, 27 reported breakthrough nausea and were included in the final analysis. Of these, 88% (N= 24) reported use of prochlorperazine and 12% (N=3) reported use of 5HT3 for treatment of breakthrough nausea. Patients in both arms experienced a reduction of nausea from baseline (Table). Unexpectedly, drowsiness also improved, by 25% for those receiving prochlorperazine. Side effects of prochlorperazine were minimal and included abdominal cramping, dry mouth and blurry vision. No toxicities were reported in the 3 pts taking 5HT3 antagonists. Conclusions: Prochlorperazine and 5HT3 antagonists were associated with a 75% reduction in breakthrough nausea. This supports the use of these drugs for breakthrough CINV. Placebo-controlled randomized control trials could be performed to confirm these observations. Median nausea reductions after taking an antiemetric (percent of baseline) Time (minutes) 30 60 120 180 240 Prochlorperazine (n = 24) 46% 50% 75% 67% 75% 5HT3RA (n = 3) 71% 75% 63% 50% 75% No significant financial relationships to disclose.