Response Predicting Biomarker And Margin Status In Local Advanced Rectal Cancer Patients With Neoadjuvant Chemoradiotherapy

Objective:To explore the predictors of the sensitivity to radiology, the mode of tumor regression and prognosis of locally advanced rectal cancer patients with neoadjuvant chemoradiotherapy, by evaluating clinicopathological characteristics, immunohistochemical biomarkers expression and gene expression.Material and Method:Retrospectively collecting locally advanced rectal cancer patients with neoadjuvant chemoradiotherapy treated in Fudan University Shanghai Cancer Center from July,2007to December,2010, accompanied by Oxaliplatin and Capecitabine, Standardized surgery with total mesorectal excision was performed after an interval of approximately6-8weeks. More than70samples were collected. Tumor residual status of surgical specimen margin were observed in10patients and analyzed with clinical data; clinicopathological change and MMR expression status immunohistochemically including MLH1and MSH2were analyzed in40patients; Gene expression profiling of29biopsy and7surgical specimens were obtained by Human Genome GeneChip Plus U1332.0Array. Discriminating genes expression difference was identified by using Significance Analysis of Microarrays (SAM). KEGG (Kyoto Encyclopedia of genes and genomes) and DAVID Functional Annotation Bioinformatics Microarray Analysis tools were used to pathway analysis.Results:Part Ⅰ:The longest tumor residual extents were6.5cm both proximally and distally. In the proximal of the tumor,the residual proportion was70%, the average residual extent was2.9cm, as those were60%and2.05cm distally; There was no significant difference about the location and the maximum diameter of the tumor between preoperative chemoradiotherapy and original ones (p=0.268, p=0.144); Tumor residual extents were usually longer than3cm when tumor located lower than peritoneal reflux or postoperative N stage was positive,(p=0.038, p=0.026); tumor residual proximal extents were not the independent prognostic factors of OS (p=0.917), while no relationship was found between the prognosis the extent or depth of the distal tumor residual; tumor residual lesions were found discontinuous and uneven, tumor regressed better in mucosa and submucosa microscopically distally. Part Ⅱ:Pathological complete response (pCR) was observed in7patients (17.5%).4patients with Dworak’s tumor regression grade (TRG) accounted for25%,47.5%cases were obtained T level downstage. Patients with MLH1positive tumor were detected in27cases (67.5%), while MSH2positive tumors were detected in23cases (57.5%). Patients with MLHl and MSH2-positive tumors were easier to get T level downstage than those with negative ones (59.3%vs23.4%, p=0.032MLHl),(73.7%vs.26.3%, p=0.049MSH2). Patients with TRG4were all detected as MLH1positive ones (p=0.009) after neoadjuvant chemoradiotherapy, with37%in sensitivity,100%in Specificity. Patients with MLH1negative tumor were found insensitive to radiotherapy.(p=0.010)Part Ⅲ:8patients were identified when expression intensity of LY6G6F>29or CD163>29as a screening criteria, and five cases of those were sensitive to radiotherapy. The correlation between the criteria and sensitivity to radiotherapy was0.358(p=0.057), sensitivity of this criteria was62.5%and71.4%in specificity. Cell cycle was determined with high expression genes significantly. Expression of CXCL12/CXCR4was low in the non-pCR group.Conclusions:Part Ⅰ:Tumor residual lesions were found discontinuous and uneven in the normal colonic wall by gross view after neoadjuvant therapy, tumor regressed better in mucosa and submucosa microscopically distally. The excision margin should not be determined only by the mucosal after neoadjuvant chemoradiotherapy.Part Ⅱ:MLHl was considered to be a possible new predictor of neoadjuvant chemoradiotherapy. Patients with MLHl negative were resistant to the chemotherapy.Part Ⅲ:Differently expressed genes determined by microarray as LY6G6F, CD163and CXCL12might be potential predictors.