Increasing Incidence of Colorectal Cancer, Starting at a Younger Age for Rectal Compared to Colon Cancer in Brunei Darussalam

Background: Colorectal cancer (CRC) is the most common gastrointestinal malignancy and is a significantcause of mortality. Its incidence is generally increasing in Asia. Reports from the West have indicated that theincidence of rectal cancer is increasing in the younger population. This study assessed the time trend of CRCin Brunei Darussalam specifically assessing the different age groups at which the incidences start to increase.Materials and
Methods: The National Cancer registry was reviewed (1991 to 2014). The age standardizedrate (ASR) and the age specific incidence rates (ASIRs) for three time periods (1991-1998), (1999-2006) and(2007-2014) were calculated.
Results: The mean age of diagnosis was 59.3±14.6 years old, incidences beingslightly higher amongst men (57.6%) and Malays (67.1%). The most common tumor type was adenocarcinoma(96.4%). Rectal cancers accounted for 35.2% (n=372/1,056) of all cancers of the large bowel; more men wereaffected than women. The proportion of rectal cancer was also high among the indigenous group. In the threetime periods, the ASR for CRC increased from 16 per 100,000 (1991-1998) to 19.6 per 100,000 (1999-2006) and24.3 per 100,000 (2007-2014). The ASIRs for CRC increased markedly between the time periods 1998-2006 and2007-2014, beginning in the 40-44 years age group. For rectal cancers, the ASIRs started to increase in the 25-29age group onward whereas for colon cancers, the increase was observed at a later age, starting from the 45-49age group.
Conclusions: Our study showed an increase in the incidence of CRC including in the younger agegroups. The increase was seen earlier in rectal cancer compared to colon cancer. These data mirror the trendsreported from the West.