Introduction
Dexamethasone (DEX) is administered for multiple days to prevent chemotherapy-induced nausea and vomiting (CINV) to patients receiving high emetogenic chemotherapy (HEC). It has also been reported that DEX has notorious side effects. Our DEX-1 trial verified sparing DEX after day2 in HEC regimen (Ito, Y, J Clin Oncol). In subgroup analysis, the benefit of DEX sparing was not clear for patients receiving cisplatin (CDDP)-based HEC regimens (CDDP regimens). Several phase 3 trials recently demonstrated that olanzapine (OLZ) improved CINV prevention in HEC. It is not clear whether addition of OLZ enables DEX sparing in CDDP regimens. Thus, this study aims to evaluate the non-inferiority of DEX sparing compared with DEX on multiple days when combined with NK1 receptor antagonist (NK-1RA), Palonosetron (Palo), and OLZ in CDDP regimens.

Methods
Cancer patients who are scheduled to receive CDDP (≥ 50mg/m2) are eligible. Patients will be randomly assigned to receive either DEX on day 1-4 or day 1 combined with NK1-RA, Palo and OLZ (5mg). The primary endpoint is complete response (CR) rate during the delayed phase (24-120hr post-CDDP administration), defined as no emesis and no rescue medications. The non-inferiority margin is set at -15.0%. We expect that CR rates would be 75% in both arms. Two hundred sixty-two patients are required for at least 80% power to confirm non-inferiority at a one-sided significance level of 2.5%. After considering the possibility of dropouts, we set our final required sample size of 280 (UMIN000032269).

Results
As of January 2019, 18 patients have been enrolled since October 2018.

Conclusions
NA

15 - PHASE III STUDY OF COMPARING DEXAMETHASONE ON DAY 1 WITH DAY 1-4 WITH COMBINED NEUROKININ-1 RECEPTOR ANTAGONIST, PALONOSETRON AND OLANZAPINE IN  CISPLATIN-BASED CHEMOTHERAPY: SPARED TRIAL