Clinicopathologic pattern and DNA methylation status of colorectal carcinoma in a group of Bangladeshi patients (PDF)

Master's Thesis from the year 2010 in the subject Medicine - Pathology, grade: A, , course: M. Phil, language: English, abstract: Colorectal cancer (CRC) is the third most common cancer in the world and the second leading cause of cancer related deaths in the United States. Globally, the incidence of CRC varies widely with higher incidence rates in North America, Australia and Northern and Western Europe (Aljebreen, 2007). The lifetime risk of developing CRC is about 6% or one in 18. Over 95% of these CRC is adenocarcinoma (Kim et al, 2010). CRC is relatively uncommon in Indian sub continent. In India the incidence of colorectal cancer was found to be 4.2 and 3.2 per hundred thousand for male and female population respectively (Afroza et al, 2007).
The incidence of colorectal cancer in Bangladesh is not exactly known, it appears to be common and occur in younger age group with slight male preponderence. Average age at diagnosis is 10 years less than the developed countries. Rectal bleeding is the most common symptoms and majority of the carcinoma were in the rectum (Hossain, 2007). The peak incidence of colorectal carcinoma is in between the age of 60 and 69 years.Fewer than 20% occur before the age of 50 years. Males are affected slightly more than females (Turner, 2010). Colorectal carcinoma are rare before the age of 40 without genetic predisposition or without predisposing factors (Hamilton, 2000). Early detection of colonic cancers is a challenging task as because clinical symptoms develop slowly. Per rectal bleeding is common. Many patients experience change in bowel habit (Yawe et al, 2007). Screening tests like digital rectal examination, simple laboratoryinvestigations like estimation of CEA, estimation of haemoglobin, faecal occult blood test,and visualization of the gut mucosa by sigmoidoscopy and colonoscopy examination may be a help in the diagnosis (Aljebreen, 2007). Colorectal cancer is a multifactorial disease process. Etiology contributing from environmental factors including diatery factors, obesity, alcohol intake, smoking, life style and genetic and epigenetic abnormalities. The molecular events that leads to CRC is heterogenous and includes genetic and epigenetic abnormalities. Genetic events in colorectal cancer is genetic alteration of the APC gene, mutations in the KRAS and P53 gene and abnormalities in the DNA mismatched repair genes (Turner, 2010). Epigenetic changes, which is the heritable changes in gene function that are not due to changes in the DNA sequence is an important pathway in the mechanism of tumerogenesis in colorectal cancer. [...]