Kato, Takeshi

203 Background: D2 gastrectomy followed by adjuvant S-1 is one of the standard therapy for the patients (pts) with stage III gastric cancer (GC) in Japan; however, the outcome is not satisfactory. We examined the efficacy of perioperative capecitabine and oxaliplatin (CapeOx) in pts with clinical SS/SE N1-3 M0 GC. Methods: The eligibility criteria included histopathologically confirmed clinical T3(SS)/T4a(SE) N1-3 M0 GC according to the Japanese Classification of GC (JCGC; 3rd English Edition). Three cycles of neoadjuvant CapeOx (NAC; capecitabine, 2,000 mg/m2 for 14 days; oxaliplatin, 130 mg/m2 on day 1, every 3 weeks) were administered, followed by five cycles of adjuvant CapeOx after D2 gastrectomy. The primary endpoint was the pathological response rate (pRR) according to JCGC ( ≥Grade 1b). Results: Thirty-seven pts were enrolled from April 2016 to May 2017, and fully evaluated for efficacy and toxicity. Thirty-three pts (89.2%) completed the planned three cycles of NAC and underwent gastrectomy, with an R0 resection rate of 78.4% (n = 29) and a pRR of 54.1% (n = 20, p = .058; 90% confidence interval [CI], 39.4–68.2) were demonstrated. The relative dose intensity (RDI) of capecitabine and oxaliplatin were 90.5% and 91.9%, respectively. Among 27 pts who initiated AC, 21 (63.6%) completed the treatment, and the RDI of capecitabine and oxaliplatin were 80.9% and 65.1%, respectively. Grade 3–4 toxicities during NAC included neutropenia (8%), thrombocytopenia (8%), and anorexia (8%) and during AC included neutropenia (37%), diarrhea (4%), and anorexia (4%), but no treatment-related death was reported. The overall survival (OS) rate and relapse free survival (RFS) rate at 3 years was 83.8% (95% CI, 72.7-96.5%) and 73.0% (95% CI, 60.0-88.8%), respectively. Subgroup analyses according to residual tumor after surgery (R status) showed a 3-year OS and RFS rate of 86.2% (95% CI, 74.5-99.7%) and 75.7% (95% CI, 63.0-90.8%) for R0. Conclusions: Perioperative CapeOx showed good feasibility and favorable prognosis with sufficient pathological response, although statistical significance at .058 did not reach the commonly accepted cutoff of .05. The data obtained using this novel approach warrant further investigations. Clinical trial information: 000021641.

106 Background: Single agent of panitumumab (Pmab) is expected to be well tolerated and to improve survival in first-line setting in patients (pts) who are not eligible for intensive chemotherapy, although the efficacy and safety of Pmab for chemotherapy-naïve frail or elderly Japanese pts with wild-type (wt) RAS unresectable colorectal cancer (CRC) have not been yet studied. Methods: We conducted a multi-center phase II study. Pts aged over 76 years, or over 65 who were considered unsuitable for intensive chemotherapy. Pmab 6 mg/kg was administered intravenously every 2 weeks. The primary endpoint was disease control rate (DCR), and secondary endpoints included progression-free survival (PFS), overall survival (OS), response rate (RR), time to treatment failure (TTF), and the incidence of grade 3 or 4 toxicities. Sample size was set to 36 with exact p-value of 0.05, a power of 0.90, the null of hypothesis of 45% and alternative hypothesis of 70% based on the Clopper-Pearson method. Results: A total 36 pts were enrolled in February 2017 to August 2018. Two pts were excluded; one was a lack of image examination at baseline, and the other was a lack of measurable lesion. The median age was 81 (67-88), with 29 pts (85%) being aged over 76 years. There were 33 (92%) pts with performance status (PS) 0/1, while two (6%) and one (3%) pts were PS 2/3, respectively. Twenty-eight pts (78%) had left-sided CRC, while eight pts had right-sided CRC. The RR was 50.0% (95%CI, 32.4-67.6) including three cases (8.8%) of complete response, and SD was 26.5%, yielding 76.5% of DCR (p < 0.001, 90% confidence interval [CI], 61.5-87.7). The RR with left sided tumor was 65% (95%CI, 44.3-82.8), while that pts with right-sided tumor was 0% (95%CI, 0.0-36.9)(p = 0.003). The major grade 3 or 4 nonhematologic toxicities were rash (n = 6, 17%), hypomagnesemia (n = 4, 11%), fatigue (n = 3, 8%), paronychia (n = 3, 6%), and hyponatremia (n = 3, 6%). The grade 3 hematologic toxicities was neutropenia (n = 1, 3%). Conclusions: Pmab monotherapy showed the favolable efficacy and feasibility in the frail or elderly pts with RAS wt, unresectable CRC. The survival analysis including OS, PFS and TTF is awaiting. Clinical trial information: UMIN000024528.