Fig. 4

(a) A nonlinear relationship between postoperative capecitabine duration and CSS was observed in stage III disease (P for nonlinearity = 0.003) but not in stage II disease (P for nonlinearity = 0.24). (b) The red curved line shows an L-shaped relationship between capecitabine duration and the risk of death in stage III elderly colon cancer after adjusting for sex, age, T stage, CA199, CEA, histological type, CCI, and MMR status. The area between the two blue dotted lines (upper limit and lower limit) is expressed as a 95% CI. The HR for death was 0.79 (95% CI, 0.68–0.92) with a postoperative capecitabine duration ≤ 16 weeks and 1.34 (95% CI, 0.91–1.97) with a duration > 16 weeks