Jianwei Zhang¹, Yanhong Deng¹, Yue Cai¹, Huabin Hu¹, Lei Huang², Meijin Huang², Liang Kang², Ping Lan², Jianping Wang²

¹Medical Oncology, The Sixth Affiliated hospital of Sun Yat-sen University, ²Surgery, The Sixth Affiliated hospital of Sun Yat-sen University

Objective:To avoid the damage of radiotherapy for rectal cancer patients, we have designed a phase II study comparing Neoadjuvant mFOLFOX6 chemotherapy with or without radiation in locally advanced rectal cancer. However, not all patients could obtain benefit from the strategy of chemotherapy alone. We aimed to develop an accurate models and nomograms to predict tumor regression grade and ypTNM down-staging for patients with locally advanced rectal cancer after preoperative chemotherapy alone. Method: From 2011 to 2015, 137 patients with locally advanced rectal cancer were enrolled into the group with preoperative chemotherapy alone. All the clinical parameters before treatment were collected. TRG 0-1 was defined as good regression, and ypTNM stage 0-I was defined as good down-staging. Nomograms to predict tumor regression and good down-staging was developed based on the result of multivariate Cox-model. The predictive performance of the model was assessed with C-index and calibration plots. Result: Of the 137 patients, 10 had TRG 0 (complete regression), 32 patients with TRG 1 and 95 patients with TRG 2 and 3 (poor regression). 56 (40.9%) patients were classified as good down-staging with ypTNM stage 0-I. Based on the multivariate Cox model and logistic regression, the predictive nomograms were successfully developed (Figure 1 and 2) to predict the probability of TRG 0-1 and good down-staging with a C-index of 0.72 (95%CI 0.604-0.797) and 0.762 (95% CI 0.681-0.844). Calibration plots demonstrated good statistical performance upon internal validation (Figure 3). Predictive factors in our models included tumor length, tumor circumferential extent, age and ApoA1. Conclusion: The model based on clinical parameters could accurately predict early efficacy with chemotherapy alone. The patients who might obtain good efficacy from neoadjuvant mFOLFOX6 chemotherapy alone could avoid radiotherapy damage. Further validation for the model is warranted with larger prospective study.

Key Words: Nomogram  Neoadjuvant chemotherapy  Rectal cancer