A nomogram for predicting cancer specific survival (CSS) in patients with pathological T3N0M0 (pT3N0M0) rectal cancer.

Abstract

113 Background: Preoperative chemoradiotherapy followed by total mesorectal excision (TME) surgery has been widely adopted as the standard treatment for stage II-III rectal cancers. However, the role of adjuvant chemotherapy in pathological T3N0M0 (pT3N0M0) patients remains controversial. A reliable prognostic model is needed to discriminate the high-risk patients from the low-risk patients, and optimize adjuvant chemotherapy treatment decisions by predicting the likelihood of adjuvant chemotherapy benefit for the target population. Methods: We gathered and analyzed 276 patients in Sun Yat-Sen University Cancer Center from March 2005 to December 2011. All patients underwent total mesorectal excision, without preoperative therapy, and were pathologically proven pT3N0M0 rectal cancer. LASSO regression model was used for variable selection and risk factor prediction. Multivariable cox regression was used to develop the predicting model. Optimum cut-off values were determined using X-Tile plot analysis. The 10-fold cross validation was adopted to validate the model. The performance of the nomogram was evaluated with its calibration, discrimination and clinical usefulness. Results: A total of 188 patients (68.1%) had adjuvant chemotherapy and no patients had adjuvant radiotherapy. Age, carbohydrate antigen 19-9 [CA199], monocyte percentage [MONO%], lymph node dissection numbers [LNDs] and nerve invasion were identified as significantly associated variables that could be combined for an accurate prediction risk of CSS for pT3N0M0 patients. The model adjusted for CSS showed good discrimination with a C-index of 0.723 (95% CI = 0.652 to 0.794). The calibration curves showed that the nomogram adjusted for CSS was able to predict 3-, 5-, and 10-year CSS accurately. The corresponding predicted probability was used to stratify high and low-risk patients. Adjuvant chemotherapy improved survival rate in the low-risk patients (HR = 0.338, 95% CI: 0.135 to 0.848, P = 0.021), while it did not exhibit a significant benefit in the high-risk patients. Conclusions: The nomogram effectively predicts CSS in patients with pT3N0M0 rectal cancer, which can be conveniently used in clinical practice. Adjuvant chemotherapy may improve overall survival in the low-risk patients. But the benefit of adjuvant chemotherapy was not seen in the high-risk patients.