Distinctive Clinico-Pathological Characteristics of Colorectal Cancer in Sabahan Indigenous Populations

Malaysia is an ethnically diverse nation, comprising Malay, Chinese, Indian and indigenous groups. However, epidemiological studies on colorectal cancer have mainly focused on the three main ethnic groups. There is evidence that the clinico-pathological characteristics of some cancers may differ in indigenous populations, namely that they occur earlier and behave more aggressively. We aimed to determine if there were similar differences in colorectal cancer, focusing on the indigenous populations of Sabah.

Histopathological reports of all patients diagnosed with colorectal carcinoma from January 2012 to December 2016 from public hospitals in Sabah were retrieved from the central computerized database of the Pathology Department of Queen Elizabeth Hospital in Kota Kinabalu, Sabah. Supplementary data was obtained from patients' case files from each hospital. Clinico-pathological data were analysed using the IBM SPSS Statistical Software Version 23 for Windows for descriptive statistics (mean, median, ASR, AR, relative risk) and inferential statistics (Chi square test).

A total of 696 patients met the inclusion criteria. The median age for colorectal cancer in Sabah was 62 years (95% CI 60.3 to 62.3), with an age specific incidence rate of 21.4 per 100 000 population. The age specific incidence rate in the indigenous populations was 26.6 per 100 000, much lower than the Chinese, at 65.0 per 100 000. The risk of colorectal cancer occurring before the age of 50 was three times higher in the indigenous population compared to the Chinese. The tumours were mainly left-sided (56.5%), adenocarcinoma in histology (98.4%) and moderately differentiated (88.7%). Approximately 79.2% of patients received curative treatment.

Indigenous populations in Sabah develop colorectal cancer at an earlier age, and present at more advanced stages. This has implications for screening and therapeutic strategic planning. 
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