Abstract
BackgroundThe incidence rate of colorectal cancer (CRC) is increasing among patients below 50 years of age. The reason for this is unclear, but could have to do with the fact that indicative variables, such as tumour location, gender preference and genetic preponderance have not been followed up in a consistent mann er. The current study was primarily conducted to improve the hereditary CRC screening programme by assessing the demographic and clinicopathological characteristics of early-onset CRC compared to late-onset CRC in northeast Iran.MethodsThis retrospective study, carried out over a three-year follow-up period (2014–2017), included 562 consecutive CRCs diagnosed in three Mashhad city hospital laboratories in north-eastern Iran. We applied comparative analysis of pathological and hereditary features together with information on the presence of mismatch repair (MMR) gene deficiency with respect to recovery versus mortality. Patients with mutations resulting in absence of the MMR gene MLH1 protein product and normal BRAF status were considered to be at high risk of Lynch syndrome (LS). Analyses using R studio software were performed on early-onset CRC (n = 222) and late-onset CRC (n = 340), corresponding to patients ≤50 years of age and patients > 50 years.ResultsFrom an age-of-onset point of view, the distribution between the genders differed with females showing a higher proportion of early-onset CRC than men (56% vs. 44%), while the late-onset CRC disparity was less pronounced (48% vs. 52%). The mean age of all participants was 55.6 ± 14.8 years, with 40.3 ± 7.3 years for early-onset CRC and 65.1 ± 9.3 years for late-onset CRC. With respect to anatomical tumour location (distal, rectal and proximal), the frequencies were 61, 28 and 11%, respectively, but the variation did not reach statistical significance. However, there was a dramatic difference with regard to the history of CRC in second-degree relatives between two age categories, with much higher numbers of family-related CRCs in the early-onset group. Expression of the MLH1 and PMS2 genes were significantly different between recovered and deceased, while this finding was not observed with regard to the MSH6 and the MSH2 genes. Mortality was significantly higher in those at high risk of LS.ConclusionThe variation of demographic, pathological and genetic characteristics between early-onset and late-onset CRC emphasizes the need for a well-defined algorithm to identify high-risk patients.
Highlights
1.2 million people suffer from colorectal cancer (CRC), the third most deadly cancer worldwide [1]
The outcomes in relation to the different characteristics studied for the two age categories are shown in Table 1; because this was a retrospective study, we were unable to collect all data for all variables investigated, which is given for each entry in the Table
We found that the mean age for early-onset CRCs was 40 years and that the highest number of cases were in the final decade of the age range investigated (40–50 years of age), which is in accordance with other studies [9, 11, 16, 48]
Summary
1.2 million people suffer from colorectal cancer (CRC), the third most deadly cancer worldwide [1]. In spite of overall decreasing CRC rates, in patients older than 50 years [2], the trend is the opposite in younger patients [3, 4]. Compared to Western World (Europe and the U.S.), the incidence of CRC is currently very low in the older Iranian population, while young Iranians are showing a rising trend [19]. The incidence rate of colorectal cancer (CRC) is increasing among patients below 50 years of age. The reason for this is unclear, but could have to do with the fact that indicative variables, such as tumour location, gender preference and genetic preponderance have not been followed up in a consistent mann er.
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