Clinicopathological And Molecular Features In Early-onset Colon Cancer Patients

Section ?Clinicopathological featuresin early-onset colon cancer patientsBackground and objectives:Colorectal cancer(CRC)has become one of the most complicated challenges of human health.In general,colorectalcanceristhought of as a disease affecting the older population,with more than 90%of patients being diagnosed after age 55.While the CRC incidence and mortality had declined significantly in older population as a result of wide adaptation of cancer screening and fiber colonoscopy examination,the incidence and mortality of early-onset colorectal cancer(EOCRC)in young patients has increased dramatically in recent years.Early-onset colorectal cancer is an independent subtype distinguished from elderly colorectal cancer,with unique clinical pathological features,molecular characteristics,and prognosis.EOCRC is often defined as an invasive disease with advanced stage at diagnosis,poor differentiation,mucinous adenocarcinoma,and signet ring cell carcinoma as the common forms,and poor prognosis.Left and right colon cancers differed much in many aspectsfrom embryonic origin to epidemiology,clinicopathological features,molecular characteristics,treatments,and prognosis.Whiletherewere increasinginterestsonthedifferencebetween left and right EOCRC,only a few reports were available.In this study,we aimed to explore the difference of the right and left sided early-onset colon cancer,including clinical,pathological features and survival.Materials and methods:From January 2004 to December 2014,187 cases of colon cancer patients aged 40 years or younger who were surgically removed and pathologically diagnosedat Qilu Hospital of Shandong Universitywere collected in this study.Among them,4 FAP cases,and 2 cases with unclear primary tumor site were excluded.Clinical characters of 181 cases,including gender,age,lesion location,family history,polyposis,smoking history,TNM stage,surgical methods,number of collected lymph nodes,pathological type,tumor grade,survival,disease-free survival,etc.were carefully collected to build up the clinical data base for further study.All patients were followed up on December 31,2017.The survival period was days from the date of surgery to the date of death.The disease-free survival period was days from the date of surgery to the date of recurrence or metastasis.According to the relation of tumor onsite location and the colon spleen curve,all patients was divided into two groups:the left colon and the right colon cancer groups.Tumors on appendix,cecum,ascending colon,hepatic flexure,and transverse colon were set as the right colon cancer group,and those on splenic flexure,descending colon,and sigmoid colon were set as left colon cancer group.According to age,they were divided into two groups:a younger cohort(30 years or yonger)and an older cohort(older than 30 years).SPSS 23.0 statistical software was used for statistical analysis.The correlation between all factors was tested by chi-square test.Kaplan-Meier method and multi-factor COX proportional hazards model were used for survival analysis.The difference was considered as statistically significant at p<0.05.Results:1.In 181 cases of early-onset colon cancer in this study,there were 51 cases(28.2%)with poor differentiation,and 79 cases(43.7%)with mucinous adenocarcinoma(including signet ring cell carcinoma and mucinous adenocarcinoma).2.The 5-year survival rate of all early-onset colon cancer patients in this study was 58.4%.5-year survival rate of left-sided colon cancer was 50.8%and of right-sided was 64.6%.5-year survival rate of<30 years group was 49.7%and of>30 years group was 66.0%.3.In early-onset colon cancer,the N stage of left colon cancer was more advanced than that of right colon cancer,and the proportion of N2 stage was 40.2%and 24.2%(p=0.02).At the same time,the clinical stage of left colon cancer was also more advanced than that of right colon cancer,and the proportion of stage ?+? was 72.0%and 51.5%,respectively(p=0.013).4.In early-onset colon cancer,the rates of less than 12 lymph nodes collected in the left colon cancer(46.3%)was significantly higher than that in the right colon(31.3%)(p =0.038).5.In early-onset colon cancer,there was no significant difference in age,sex,differentiation,ratio of mucinous adenocarcinoma,R0resection rate,and family history between left and right colon cancer group(p>0.05).6.Univariate analysis showed that,compared with left colon cancer,right colon patients of stage ?-? had an increasing trend of DFS(HR 0.718,95%CI 0.475-1.083,p=0.091)and OS(HR 0.688,95%CI 0.444-1.066,p=0.092).Patients with stage ?-? right colon cancer were more likely to have increased DFS(HRO.662,95%CI 0.370-1.182,p=0.16)and OS(HR 0.608,95%C10.321-1.153,p=0.123)than those with left colon cancer.There was no significant difference in OS in stage IV patients between left colon and right colon cancer(HR0.913,95%CI 0.497-1.676,p=0.769).7.In early-onset colon cancer,thegroupaged?30 years had more distant metastasis(33.7%and16.9%,p=0.009),and a low R0 resection rate(66.3%and85.4%,p=0.003).8.In early-onset colon cancer,thegroup aged?30 years had less family history(3.3%and 18.0%,p=0.001).9.There was no significant difference in the gender,location,differentiation,mucinous adenocarcinoma ratio,and the number of lymph nodes collected less than 12 between aged?30 years and aged>30 years group(p>0.05).10.Univariate analysis showed that,compared with patients under the age of 30,patients over the age of 30 in the ?-? group had significantly better DFS(HR0.579,95%CI 0.380-0.882,p=0.006)and OS(HR0.608,95%CI 0.390-0.948,p=0.026).For ?-? period patients,the group above 30 had an increased trend but no statistical difference in DFS(HR 0.721,95%CI 0.404-1.287,p=0.266)and OS(HR 0.789,95%CI 0.417-1.490,p=0.464)compared with less than 30-year-old group.No significant difference was found in OS between patients above and less than 30 years old in stage ?(HR 0.920,95%CI 0.479-1.765,p=0.802).11.Multivariate analysis found that tumor site and age were not independent factors of DFS in both ?-? and ?-? phases;and not independent factor of OS in ?-?,?-?,and ? phases.Conclusion:1.The proportion of poorly differentiated cancer and mucinous adenocarcinoma was relatively high in early-onset colon cancer.2.The clinical stage of left colon cancer was more advanced than that of right colon cancer and survival rate of left colon cancer was even worse in early-onset colon cancer patients.3.More distant metastases,low R0 resection rate and worse survival were associated with patients aged?30 years.4.Multivariate survival analysis showed that tumor site and age had no effect on disease-free survival and overall survival.Section ? Molecular features in early-onset colon cancer patients Background and objectives:Colon cancer is a highly heterogeneous disease.Tumors with similar clinicopathologic features may have different molecular pathogenesis,biological behavior,clinical behavior,outcome,and treatment response to certain drugs.To date,three main pathways involved in the formation and development of CRC have been identified:the chromosomal instability(CIN)or suppressor pathway,the microsatellite instability(MSI)or mutator pathway,and the CpG island methylator phenotype(CIMP)or serrated pathway.Compared with late-onset CRC,early-onset CRC expresses unique molecular features,with a high proportion of MSI-H,more POLE mutations,and less BRAF,KRAS mutations.A growing amount of evidence has unveiled distinct gene expression profiles and genetic alterations in right and left-sided CRC.There are more BRAF mutations,KRAS mutations,and PIK3CA mutations in the right sided colon cancer,and MSI-H,CIMP-H,CMS1,and CMS3 are more common.However,there are less BRAF mutations and KRAS mutations in the left sided colon cancer and MSS,CIN,CMS2,and CMS4 are rare.Correlation studies have received increasing attention,including embryonic origin to epidemiology,clinicopathological features,molecular characteristics,treatment,and prognosis.However,there has been no report on the the correlation between molecular typing and tumor location of EOCRC.In summary,we try to to analyze the correlation between molecular features of early-onset colon cancer(aged 40 years and younger)and prognosis with respect to tumor location.By exploring the molecular characteristics and survival differences in terms of tumor location(right-versus left-sided)in early-onset colon patients,this study aims to provide a theoretical basis for the individual treatment of early-onset colon cancer in the future,Materials and methods:From January 2004 to December 2014,43 cases of colon cancer patients aged 40 years or younger who were surgically removed and pathologically diagnosedat Qilu Hospital of Shandong Universitywere collected in this study.Clinical characters,including gender,age,lesion location,family history,polyposis,smoking history,TNM stage,surgical methods,number of collected lymph nodes,pathological type,tumor grade,survival,disease-free survival,etc.were carefully collected to build up the clinical data base for further study.Patients were observed until death or Dec 31,2017,whichever came first.The survival period was from the date of surgery to the date of death,and the disease-free survival period was from the date of surgery to the date of recurrence or metastasis.43 cases of tumor paraffin samples were collected for NGS sequencing(Nanjing Shihe Gene Biotechnology Co.,Ltd.),while paraneoplastic paraffin samples and whole blood were used as negative controls.MSI score?0.18 was defined as MSS,MSI score?0.4 was defined as MSI-H,and score between 0.18-0.4 was MSI-L.The patients whose values of TMB?31 were divided into high TMB group,the patients whose values of TMB?7 were divided into low TMB,and the patients between 7-31 were divided into medium TMB.According to the relation of tumor onsite location and the colon spleen curve,all patients was divided into two groups:the left colon and the right colon cancer groups.Tumors on appendix,cecum,ascending colon,hepatic flexure,and transverse colon were set as the right colon cancer group,and those on splenic flexure,descending colon,and sigmoid colon were set as left colon cancer group.According to age,they were divided into two groups:a younger cohort(30 years or yonger)and an older cohort(older than 30 years).SPSS 23.0 statistical software was used for statistical analysis.The correlation between all factors was tested by chi-square test.Kaplan-Meier method and multi-factor COX proportional hazards model were used for survival analysis.The difference was considered as statistically significant at p<0.05.Results:1.According to the NGS results,287 mutations were found in the early-onset colon cancer.And a total of 20 g.ermline mutations(46.5%)were found,including 13 MMR,3 POLE,2 APC,1 POLD1,and 1 APC-MMR Germline mutations.2.In all mutation genes,DDR2,FBXW7,FGFR2,and TET2 were found to be significantly more in the right sided colon(22.7%vs 0%,p=0.020).3.In all cases,there were 28 MMR mutations(65.1%),of which 8 were inactivating mutations.4.In all cases,9 were MSI-H(20.9%),and 22 were KRAS mutations(51.2%).HRAS mutations occurred in 2 patients(4.7%),NRAS mutations in 1(2.3%),BARF mutations in 3(7.0%),TMB-H in 15(34.9%),and POLE mutations in 8(18.6%).5.Patients over 30 years had higher MSI-H ratio(35.0%and 8.7%,p=0.034)and higher TMB ratio(55.0%and 17.4%,p=0.010)than those age under 30.6.TMB was highly correlated with MSI(r=0.703,p<0.0001).7.Thevaluesof TMB in the MSI-H group(31.1-84.4mutations/Mb,mean 52.3,median 40.0)were much higher than those in the MSS group(1.1-134.4mutations/Mb,mean 22,5,median7.78),also the values of TMB in the POLE mutation group(4.4-134.4/Mb,mean 70.6,median 76.7)were much higher than in the POLE wild group(1.1-73.3/Mb,mean 19.0,median 8.9).8.Univariate analysis showed that MSI-H,KRAS mutations,high TMB and POLE wild-type had certain survival advantages in DFS and OS,but did not reach statistical significance.9.Multivariate survival analysis showed that MSI,KRAS,TMB,andPOLE had no effect on DFS and OS.Conclusion:1.Early-onset colon cancer was hereditary and there were more gene mutations in the right sided colon.2.There were significant differences in gene mutations including DDR2,FBXW7,FGFR2,and TET2between left and right sided colon.3.In early-onset colon cancer patients,MSI-H and high TMB status were more common in patients over 30-year age.More over,TMB was highly correlated with MSI.4.The values of TMB in the MSI-H group were much higher than those in the MSS group,also the values of TMB in the POLE mutation group were much higher than those in the POLE wild group.5.This study found that MSI,TMB,KRAS mutations,and POLE mutations had no effect on survival in early-onset colon cancer patients.