The continuing problem of post chemotherapy nausea and vomiting: contributions of classical conditioning.

Despite continuing improvements in antiemetic therapies, nausea and vomiting following chemotherapy treatments for cancer remain significant clinical problems for many patients. The role of classical conditioning in patients' anticipatory nausea is well known, but little attention has been paid to possible conditioning effects on post treatment nausea. The present study statistically examined the contribution of anticipatory (conditioned) nausea to patients' subsequent post treatment nausea. Forty early stage breast cancer patients who developed anticipatory nausea were analyzed. Results revealed a significant correlation between the intensity of anticipatory nausea in the clinic prior to their treatment infusion and subsequent post treatment nausea during the 24 h after the infusion. These results provide support for the hypothesis that, once established, conditioned nausea may contribute to the severity of subsequent post treatment nausea in patients receiving repeated cycles of chemotherapy for cancer. The results suggest the importance of considering the contribution of conditioning process to nausea and other post treatment side effects.