Role Of Postoperative Radiotherapy For PT3N0 Rectal Cancer

Objective p T3N0M0 rectal cancer is a subgroup with low risk of recurrence in patients with locally advanced rectal cancer,in which the postoperative radiotherapy is controversial.We aimed to define risk factors of cancer specific survival(CSS)for p T3N0 rectal cancer and establish a scoring system to predict value of postoperative radiotherapy,and to guide the treatment of rectal cancer.Methods and Materials Based on the Surveillance,Epidemiology and End Results(SEER)database(2010–2014),patients surgically staged T3N0 rectal cancer without neo-adjuvant radiotherapy were enrolled.Screening of prognostic factors and determining of risk factors were accomplished by Cox proportional hazards model.Survival was compared by Kaplan-Meier and Log-rank test.The endpoint was CSS.Results A total of 6807 cases were reviewed,and 1021 patients were finally identified from the SEER database.Among them,635 cases in surgery alone and 386 cases in surgery with adjuvant radiotherapy.Median follow up time was 55.8 months(25.3-84.2 months).The 5 year-CSS was 86.31% for the whole cohort.Age,marital status,histology,tumor differentiation,number of nodes resected,radiotherapy and chemotherapy were associated with CSS by univariate analysis.Age ? 70 years,grade III/IV,number of nodes resected < 12,marital status(“never married” and “widow/divorced”)and absence of radiotherapy predicted poor CSS by multivariate analysis(P<0.001,P=0.044,P=0.032,P=0.005 and P=0.006,respectively).Two risk stratifications were generated based on the scoring system which was composed by age,tumor differentiation and number of nodes resected.The 5-year CSS was 92.13% for low risk patients(score < 2.5)and 72.55% for high risk patients(score ? 2.5)(P < 0.001).For low risk patients,5 year-CSS was comparable with 93.4% for patients with surgery alone and 96.4% for patients with adjuvant radiotherapy(P = 0.182).For high risk patients,5 year-CSS was double increased from 42.1% to 91.0% by addition of radiotherapy(P=0.001).Conclusions Age ? 70 years,grade III/IV,number of nodes resected <12 predicted adverse oncological outcome for p T3N0 rectal cancer after radical surgery.The scoring system could help to distinguish a particular subgroup of patients that potentially benefit from postoperative radiotherapy.