Nomogram incorporated the number of adjuvant chemotherapy cycles for predicting the prognosis in stage II-III rectal cancer patients without neoadjuvant therapy.

Abstract

e15163 Background: Current recommendations for adjuvant chemotherapy in rectal cancer are based on the studies in colon cancer. However, it is now known that rectal cancer differs from colon cancer significantly regarding clinical course and biology. No RCTs in the TME era have evaluated the value of postoperative chemotherapy and are unlikely to be performed as neoadjuvant treatment has become a “gold standard” approach. However, we found that not all patients with locally advanced rectal cancer underwent neoadjuvant chemoradiotherapy before TME in real-world clinical practice in China. Whether the number of adjuvant chemotherapy cycles is significantly related to the prognosis of these patients deserves further study. Methods: A total of 246 patients with stage II-III rectal cancer from January 2013 to April 2018 were enrolled. All patients underwent surgery and had not received neoadjuvant therapy. The survival curve was drawn by the Kaplan-Meier method, and the log-rank method was used for statistical analysis. The Cox proportional hazard model was used for multivariate analysis to determine the independent prognostic factors. Then, MFP(Multiple Fractional Polynominal) and stepwiseAIC were used for variable selection. The R software was used to establish the nomogram. The bootstrap method was employed to internal verification. Concordance index(C-index) was applied to evaluate the predictive power of nomogram. Calibration curves were drawn to compare the 3-year overall survival rate predicted by nomogram and that of actual observation. Results: 87.8% of patients received adjuvant chemotherapy including oxaliplatin combined with fluorouracil or capecitabine. Univariate and multivariate analysis showed that the number of adjuvant chemotherapy cycles was independent prognostic factors. Patients who received more than 5 cycles of chemotherapy (HR = 0.09, 95%CI(0.01,0.80)) had a significantly better overall survival than patients with less than 5 cycles (HR = 0.33,95%CI(0.12,0.89)) or no chemotherapy (p < 0.05).Through MFP and the stepwiseAIC screening, a nomogram was established based on CEA, PLR, N, and the number of chemotherapy cycles, and the C-index of the model was 0.86. Conclusions: The number of adjuvant chemotherapy cycles is an independent prognostic factor in stage II-III rectal cancer patients without neoadjuvant therapy. Moreover, nomogram incorporated the number of chemotherapy cycles was accurate and visible.