<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>We recently reported the relapse-free survival (RFS) significance of the combination of CD4<jats:sup>+</jats:sup> and forkhead box P3<jats:sup>+</jats:sup> (FOXP3) T-cell densities identified by immunohistochemistry in patients with stage I, II, and III colorectal cancer (CRC) who underwent curative resections. This study was designed to determine the optimal combination of markers that predict recurrence in patients with T factors of T3/T4a stage II CRC by applying a novel Bayes decision rule.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>Using 137 cancer tissue specimens from T3/T4a stage II patients, 12 clinicopathologic and immune factors were analysed as predictive candidates for recurrence.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Our study showed that the combination of low CD4<jats:sup>+</jats:sup> and low FOXP3<jats:sup>+</jats:sup> T-cell densities resulted in extremely poor RFS.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Adjuvant chemotherapy may be considered for patients with a combination of low CD4<jats:sup>+</jats:sup> and low FOXP3<jats:sup>+</jats:sup> T-cell densities. The discovery of this new prognostic indicator is important for the appropriate management of patients undergoing curative resection for T3/T4a stage II CRC.</jats:p> </jats:sec>