The Efficacy Of Postoperative Radiotherapy For Locally Advanced Rectal Cancer Without Neoadjuvant Therapy

Background: In the 2018 National Comprehensive Cancer Network(NCCN),the standard treatment plan recommended for patients with stage II and stage III rectal cancer is neoadjuvant radiotherapy combined with total mesorectal resection after concurrent chemotherapy.However,only 55% of rectal cancer patients actually receive preoperative radiotherapy and chemotherapy in the United States.Because of the longer period of neoadjuvant therapy,the longer waiting time before surgery,the cost of preoperative treatment is higher,the preoperative staging is not accurate,and some early patients(T1~ T2)receive overtreatment in our country,most patients did not receive the neoadjuvant treatment recommended by NCCN.The NCCN guidelines do not include specific treatment recommendations for postoperative adjuvant radiotherapy for patients with locally advanced rectal cancer who have not received neoadjuvant therapy.The purpose of this study is to evaluate the efficacy of postoperative adjuvant radiotherapy for locally advanced rectal cancer who have not received neoadjuvant therapy before surgery.Methods: Survival was evaluated in 9,585 patients who underwent surgical resection for stage II or III rectal cancer and were registered in the Surveillance,Epidemiology,and End Results-Medicare data base between 1992 and 2009.Overall survival(OS)benefit in propensity score(PS)-matched patient cohorts were estimated by Cox proportional hazards models.Results: After stratification by chemotherapy regimen,there was no significant difference in OS with or without radiotherapy among stage II patients(P=0.073).Also,there was no significant difference in OS between the 5-FU and 5-FU/radiotherapy treatment groups(P=0.914).In the PS-matched cohorts,the differences in OS in the No-treatment and Radiotherapy groups were not significant(P=0.430).The difference in OS between the 5-FU and 5-FU/radiotherapy groups was not significant(P=0.815).The difference in OS of stage III patients between the no-treatment and radiotherapy groups was significant(P<0.001).However,there was no significant difference in OS of stage III patients between 5-fluorouracil(5-FU)and 5-FU/radiotherapy groups(P=0.267).Also,the difference in OS between the FOLFOX and FOLFOX/radiotherapy groups was not significant(P=0.649).The PS-matching analysis confirmed aforementioned results.Conclusions: The evidence obtained in this study does not support postoperative radiotherapy for stage II rectal cancer or stage III patients who received postoperative chemotherapy.The use of postoperative radiotherapy for stage III patients who did not receive postoperative chemotherapy could increase OS.