Survival comparison and prognostic nomogram development for stage III rectal cancer with positive tumor deposits...

To compare overall survival (OS) between neoadjuvant chemotherapy (NACT) and adjuvant chemotherapy (ACT) in stage III rectal cancer with tumor deposits (TD), and to develop and validate an ACT-based nomogram for individualized prognostic risk stratification.

The study included 3060 stage III rectal cancer patients with tumor deposits from the SEER database (2010-2017). Propensity score matching (1:1 PSM) addressed treatment bias. The adjuvant chemotherapy cohort (n = 1520) was divided into training (n = 1,064) and validation (n = 456) sets at a 7:3 ratio. Multivariable Cox regression analysis identified prognostic factors for nomogram construction. Model performance was assessed via C-index, AUC, and calibration curves. Patients were classified as high-risk and low-risk groups based on the nomogram scores. KM curves were used to compare the survival differences between the two patient categories.

After 1:1 PSM (497 vs. 497), ACT showed significantly better OS than NACT (log-rank P = 0.0027). In the ACT cohort (n = 1520), a nomogram integrating age, CEA, PNI, T stage, and N stage achieved AUCs of 0.711/0.713/0.716 at 1/3/5 years in the training set and 0.694/0.724/0.698 in the validation set. Using an optimal cut-off of 134.55, patients were stratified into low- and high-risk groups with significantly different OS (P < 0.0001).

The nomogram was constructed to successfully predict the 1-, 3- and 5-year OS for patients who received adjuvant chemotherapy. In addition, this nomogram may assist in developing clinical treatment strategies for patients with tumor deposits who are undergoing treatment.