Phase II multicenter study of adjuvant S-1 for colorectal liver metastasis: Survival analysis of N-SOG 01 trial

Purpose: We previously showed that S-1 after curative resection of colorectal liver metastasis had acceptable toxicity and a high rate of completion of therapy in a prospective phase II trial. We here reported the primary endpoint of disease-free survival (DFS). Methods: Between October 2008 and August 2010, 60 patients were eligible for this study and received S-1 for 28 days followed by a 2-week rest period. Treatment was started within 8 weeks after surgery and repeated for eight cycles. Results: Median follow-up was 41 months. Among 60 patients, 45 had solitary metastasis, and the median maximum tumor diameter was 2.6 cm. The 3-year DFS and overall survival were 47.4 and 80.0 %, respectively. Recurrences developed in 31 patients, with the remnant liver the most common site (19 patients). Multivariate analysis showed that positive lymph node metastasis around the primary site (p = 0.013) and early liver metastasis (synchronous disease or metachronous disease within 12 months) (p = 0.041) were independent poor prognostic factors for DFS. Patients having both risk factors had a significantly worse DFS than those without these risk factors (p < 0.001). Early liver metastasis was an independent indicator of early recurrence within 1 year. Conclusions: S-1 after curative liver resection yielded promising survival in patients with a low tumor burden. Outcome in patients having both positive lymph node metastasis around the primary site and early liver metastasis was much worse than in patients without these conditions; therefore, they might warrant more aggressive therapy.