Application Of Tumor Volume By MR In Subgroup Of T3 Low Rectal Cancer

Objective: To evaluate the feasibility and the affection of neoadjuvant chemoradiotherapy(CRT)in subgroup of mr T3 low rectal cancer, we based on the size of primary tumor volume by high-resolution MR measurement from prior treatment. Methods:A total of 187 patients with mr T3(based on high- resolution MR) low rectal cancer treated in the Department of Colorectal Surgery of Fujian Medical University Union Hospital from June 2010 to December 2012 were divided into neoadjuvant chemoradiotherapy group(CRT group)(88 cases) and no neoadjuvant chemoradiotherapy group(n CRT group)(99 cases) according to whether the patients underwent CRT.we measured the depth of tumor infiltration mesorectum and mr PTV by MR from prior treatment, and analyzed the relations between them through Pearson rank correlation test.Through the receiver-operating characteristic curve(ROC) to analyze the relations between the mr PTV and disease-free survival, we got the best cutoff point value, then divided patients into subgroup mr T3-1and mr T3-2, comparing the difference between the two groups of prognosis.Afterward, The prognoses of the two groups and their subgroups were compared.Results: For n-CRT group:1.the depth of tumor infiltration mesorectum and the mr PTV revealed significantly correlated(p<0.001,double,r=0.418),that mr PTV could be used as the basis for the subgroup. 2.The average mr PTV is 16.41±10.32( 2.07-56.52) cm3. With 73 cases mr T3 a group, the average is 14.35±9.52(2.072-51.19)cm3; 26 cases mr T3b+c group, the average is 22.20±10.48(7.57-56.52)cm3。3.Through ROC curve, we got the best mr PTV cutoff point value 15cm3,the area under the curve was 0.829(95% CI=0.745-0.913, p<0.001)。We divided the patients into mr T3-1(mr PTV≤15cm3)and mr T3-2(mr PTV>15cm3).For the overall mr T3 period:1.the CRT and n CRT groups revealed significant differences in the 3-year disease-free survival rate(86.9% vs.71.8%,p=0.007)and the distant metastases rate(9.7%vs.19.0%,p=0.034)and the localrecurrence rate( 3.6%vs.12.5%, p=0.028); 2.The subgroup mr T3-1(mr PTV≤15cm3)and mr T3-2(mr PTV>15cm3)revealed significant differences in the 3-year disease-free survival rate(86.6%vs.64.6%,p<0.001)and the distant metastases rate( 8.9%vs. 23.0%, p=0.001) and the local recurrence rate(4.7%vs.16.7%,p=0.004); For subgroup mr T3-1(mr PTV≤15cm3), the CRT and n CRT groups revealed no significant differences in the 3-year disease-free survival rate(86.8% vs 85.7%,p=0.962)and the distant metastases rate(7.4% vs 9.7%,p=0.861)and the local recurrence rate( 4.1%vs5.0%,p=0.908); For subgroup mr T3-2( mr PTV>15 cm3), the CRT and n CRT groups revealed significant differences in the 3-year disease-free survival rate(84.2% vs. 51.1%,p=0.001)and the distant metastases rate(13.1% vs. 31.2%,p=0.017)and the local recurrence rate(2.9%vs26.6%,p=0.009);3. COX regression analysis was utilized for 3-year disease-free survival, the univariate and multivariate analysis indicated that CRT( OR=4.258,CI=1.912-9.483,p < 0.001), mr PTV( OR=0.381,CI=0.181-0.804,p=0.011) and circumferential resection margin( CRM)(OR=0.227,CI=0.097-0.532,p=0.001)are independent impact factors, respectively. Conclusion: 1.The volume of T3 low rectal cancer from prior treatment revealed significantly correlated with the depth of tumor infiltration mesorectum. When mr PTV took 15cm3,it could be the optimal cut-off value for subgrouping, so the mr PTV could be used as a new parameter of mr T3 period of subgrouping;2.The CRT, mr PTV and CRM are independent impact factors of prognosis of patients with low rectal cancer, respectively;3.CRT can improve the prognosis of patients with mr PTV > 15cm3 low rectal cancer but may not significantly influence the prognosis of patients with mr PTV≤15cm3 and CRM-negative low rectal cancer; surgical treatment can be performed in these patients without CRT.