Treatment for chemotherapy-induced nausea and vomiting CINV has improved signi cantly with the development of antiemetic drugs. We conducted a prospective observational study to clarify the quality of life QOL impact of antiemetic therapy recommended by the Japanese Cancer Therapy Association JSCO guidelines for Japanese breast cancer patients receiving an anthracycline plus cyclophosphamide regimen ACR. This was an open, single-center, prospective observational study conducted in Yokohama City University Medical Center. Antiemetic therapy recommended by the JSCO guidelines was implemented for all cases treated therein i.e., aprepitant, dexamethasone, and palonosetron. The primary endpoint was no impact on daily living NIDL rate during a 120-hour period following chemotherapy i.e., overall phase. We use the Japanese version of the Functional Living Index-Emesis FLIE to evaluate the impact of CINV on QOL. There were 118 analyzable cases. The NIDL rate during the overall phase was 44.9 , and was signi cantly lower than the complete response CR rate of 58.5 i.e., no emetic responses and no rescue medication ; P 0.037. Age 55 years P 0.008 and a history of morning sickness P 0.005 were identi ed as independent risk factors of NIDL P 0.05. Among Japanese breast cancer patients receiving ACR and a combination of aprepitant, dexamethasone, and palonosetron, the NIDL rate was relatively low at approximately 45. A more effective antiemetic therapy should therefore be developed for patients QOL that takes NIDL risk factors into account. In addition, our results suggested that the CR rate is insuf cient for evaluating the effect of antiemetic therapy on a patient s QOL.