Introduction: Tumor extension, as reflected by T classification, is a key prognostic factor in rectal cancer. However, the prognostic significance of the actual tumor size, particularly maximum diameter, remains less clear. This study aimed to evaluate the impact of primary tumor size on long-term survival in patients with rectal cancer (RC) undergoing curative surgery.

Methods: A retrospective analysis was conducted on 182 consecutive RC patients who underwent curative surgical resection. Tumor size, measured with a hand ruler during macroscopic pathological examination, was analyzed as a categorical variable. Receiver-operating characteristic (ROC) curve analysis was applied to determine the optimal cutoff value—defined as the maximum sum of sensitivity and specificity—for prognostic stratification. Kaplan–Meier survival curves and log-rank tests were used to assess the association between tumor size and overall survival (OS). Statistical significance was set at P < 0.05.

Results: The cohort included 101 males (55.5%) and 81 females (44.5%) with a mean age of 57.8 ± 14 years. ROC analysis identified an optimal tumor size cutoff of 5 cm (AUC = 0.61, sensitivity = 61.0%, specificity = 56.5%, Youden index = 0.17) (Fig1). Based on this threshold, patients were categorized into ≤5 cm and >5 cm groups. The median follow-up was 38 months (range 1–120 months), during which 90 patients (49.5%) died. One-, three-, and five-year OS rates for tumors ≤5 cm were 92%, 65%, and 53%, respectively, compared with 74%, 52%, and 40% for tumors >5 cm (P = 0.02)(Fig2).

Conclusions: Primary tumor size is an independent prognostic factor for OS in rectal cancer. Patients with tumors ≤5 cm demonstrated significantly better survival outcomes following curative surgery. Incorporating tumor size into prognostic assessment may improve risk stratification in RC management. Keywords: rectal cancer, overall survival, tumor size, prognostic factor. .