Efficacy and Safety Comparison of S-1 and Capecitabine in Metastatic Colorectal Carcinoma: A Systematic Review and Meta-Analysis.

S-1 and capecitabine are both oral chemotherapy options often used to treat metastatic colorectal cancer (mCRC). Their effectiveness and side effects have generated clinical interest, particularly in deciding which one to use. This review aimed to directly compare the two regimens in terms of outcomes and tolerability. Our study was conducted in accordance with PRISMA guidelines. A comprehensive search of PubMed/MEDLINE, Web of Science, and Google Scholar identified five eligible studies for the systematic review and meta-analysis. Primary outcomes were objective response rate (ORR) and disease control rate (DCR); secondary outcomes included progression-free survival (PFS) and overall survival (OS). The analysis included 1,414 patients from five studies. S-1-based regimens showed a trend toward a higher ORR than capecitabine, with a pooled risk ratio of 1.14 (95% CI: 0.99-1.32; p = 0.07), though this difference did not reach statistical significance. There was no significant difference in DCR between the two groups (RR = 0.91, 95% CI: 0.46-1.83; p = 0.80), with substantial heterogeneity observed (I² = 66%). For the secondary outcomes, meta-analyses of PFS and OS could not be conducted due to insufficient data; however, descriptive analyses showed no statistically significant differences between the two regimens. Compared to capecitabine, S-1 was associated with significantly lower rates of hand-foot syndrome (HFS). However, the incidence of stomatitis was higher in the S-1 group. S-1 was comparable in efficacy to capecitabine and may be particularly beneficial for patients who are intolerant to capecitabine-associated adverse events (AEs), especially HFS.