Development of a Genome-based Platform for Personalized Treatment in Locally Advanced Rectal Cancer Patients

This study is aimed to develop a genome-based platform to predict patients who can achieve pathologic complete response after neoadjuvant treatment in locally advanced rectal cancer. The main treatments for locally advanced rectal cancer is surgical removal such as lower anterior resection after neoadjuvant CCRT. About 10-40% of patients showed pathologic complete response after neoadjuvant CCRT. Mandard tumor regression grade (TRG) is used to grade the histologic tumor response after neoadjuvant treatment. TRG 1 represents the pathologic complete response and TRG2 as histologically small group of cancer cells. Accordingly, TRG1 and 2 are expressed as good responder. Even though the surgery is being performed as an essential treatment, there are various surgery-related sequelae such as colostomy. Also, in some patients, surgery may be refused or surgery may not be performed due to an underlying disease. About 15-20% of local recurrence was reported in patients who did not undergo surgery and the 3-year survival rate was 96.6%. Colorectal cancer genetically can be divided into 4-subtypes. With the recent development of genome testing technology, genome analysis has been actively conducted in colorectal cancer. The most commonly known genetic subtype of colorectal cancer is classified into a total of 4 types as consensus molecular subtype (CMS); CMS1, CMS2, CMS3, CMS4. However, this was analyzed in colorectal cancer patients who did not undergo radiotherapy. There is no data regarding the response to radiation therapy according to each genetic subtype. Therefore, classifying the subtypes through genomic analysis and studying the responsiveness to radiotherapy in each subtype is needed. In this study, we aimed to develop a platform that predicts pathologic tumor response after CCRT based on genomic information. Furthermore, being able to select patients who can wait-and-see without surgery using platform.