Prognosis And Predictors After Neoadjuvant Therapy For Local Advanced Rectal Cancer

ObjectiveTo explore the clinical and imaging factors influencing the prognosis after preoperative radiotherapy for local advanced rectal cancer,and to guide the treatment of rectal cancer.Methods and MaterialsWe retrospectively analyzed 88 patients with locally advanced rectal cancer between April 2010 to September 2015.Forty-four patients(50.0%)underwent neoadjuvant short-course radiotherapy,and the other 44 patients(50.0%)underwent neoadjuvant long-course chemo-radiotherapy.Tumor ADC values of post-RT were measured by Diffusion-weighted MRI technology.The slides of surgical specimens were reviewed and classified according to Mandard TRG.We compared patients with good response(Mandard TRG1+2)and patients with poor response(Mandard TRG3+4+5).The relationship between ADC values of post-RT and TRG was analysised.Survival rate was constructed using the Kaplan-Meier method.Using Cox regression proportional hazards model and log Rank tests analyze the prognostic factors for survival.ResultsIn univariate analysis,age(P=0.006),adjuvant chemotherapy(P=0.023),pathological type(P=0.024),differentiation degree(P=0.001),distance from tumor to the anal margin(P=0.031)and TRG(P=0.007)were significantly associated with overall survival(OS).Multivariate analysis showed that TRG(P=0.034)were independently prognostic of OS.There was no significant difference in OS between the long-course chemo-radiotherapy group and short-course radiotherapy group(P=0.261).The 5-year OS between TRG1+2 and TRG3+4+5 was significant(90.9%vs 67.4%,P=0.004).Neoadjuvant radiotherapy(P=0.000),pT(P=0.010),gross type(P=0.020)and ADC values of post-RT(P=0.002)were significantly associated with TRG.The best critical point of ADC values of post-RT was 1.71×10-3mm2/s by using ROC curve.The accuracy of ADC values of post-RT in predicting TRG was68.8%.The patients with low CEA level before radiotherapy had higher tumor ADC values of post-RT(ADC ≥ 1.71 × 10-3mm2/s),and the difference was statistically significant(P=0.024).ConclusionsThere was no significant difference in OS between long-course chemo-radiotherapy and short-course radiotherapy group.TRG can predict the efficacy of neoadjuvant long-course or short-course radiotherapy in patients with locally advanced rectal cancer.The ADC values of post-RT in patients with locally advanced rectal cancer may predict TRG after neoadjuvant radiotherapy.