Value of tumor size as a prognostic variable in colorectal cancer: a critical reappraisal

Vertical tumor growth, reflected by T classification, represents the most important prognostic variable in colorectal cancer. Our study aimed to investigate the impact of tumor size, particularly the maximum tumor diameter, on outcome of affected patients.

A total of 381 colorectal cancer specimens were re-evaluated. Tumor size and location were extracted from the medical history and were known for 359 patients (94%). Receiver-operator characteristic analysis was applied to identify the optimal (maximum of sum of sensitivity and specificity) cut-off values with respect to prognostic impact.

Median tumor size was 4.5 cm (range, 0.6-15). Tumor size exceeding 4.5 cm was observed in 159 patients (44%) and was associated with high T and N classification, UICC stage, and tumor grade. At median follow-up of 45 months (range, 0-180), 141 patients (40%) showed tumor progression. Although 4.5 cm was identified as the optimal cut-off value within the whole group of patients, receiver-operator characteristic analysis restricted to different parts of the large bowel determined 5 cm, 5.3 cm, 3.9 cm, and 3.4 cm as cut-off values with the strongest discriminatory capacity in colon, right-sided colon, left-sided colon, and rectum cancers, respectively. Applying these cut-off values, tumor size was significantly associated with progression-free and cancer-specific survival in univariate and multivariate analyses in colon, yet not in rectum cancers.

Tumor size proved to be an independent prognostic parameter for patients with colorectal cancer. Optimal cut-off values vary among different parts of the large bowel. Whereas prognostic significance is strong within the colon, it appears to be of minor value within the rectum.