Euxian, Lee
(2014)
A case control study on relationship of colorectal cancer and smoking exposure in Hospital Universiti Sains Malaysia.
Masters thesis, Universiti Sains Malaysia.
Abstract
Background: There have been inconsistent findings in the association between colorectal
cancer and smoking exposure. Most reported data were from western population groups with
only few involving Asian population while there’re no available local data from Malaysia. As
the causes of colorectal cancer are multifactorial, the genetic susceptibility, lifestyle and diet
difference between Western and Asian population may be important in determining the
overall individual risks across the world.
Methods: This study investigates such association in our local population at Hospital
Universiti Sains Malaysia in Kelantan. Our case-control study involves patients diagnosed
with colorectal cancer from 2005 till 2011 which is matched to a group of controls without
the tumour. Data were collected from the patients file records and supplemented further by
phone interviews or clinic follow up to complete the validated study proforma. We included a
total of 92 cases matched with 92 controls.
Results: Current regular smokers have an overall significant association and increased risk of
developing CRC (OR = 2.26: CI 95% 0.90-5.89). Increasing number of cigarettes smoked per
day is related towards higher rectal cancer risk as compared to colon cancer (p value 0.009).
There’s statistically no significant association between dose-duration of cigarette smoking and
the CRC risk however we find those who smoked over 30 years and had more than 20
cigarettes / day had higher OR of 1.92 compared to 1.42 of developing CRC in non-smokers.
The cessation of smoking for 30 years could eventually reduce the OR to 1.13 closer to the
baseline of non-smokers however again the data is statistically non significant.
Conclusion: We report a positive association of CRC risk in current smokers among our local
population at Hospital Universiti Sains Malaysia in Kelantan with heavy smokers having a
higher incidence of rectal cancer. The link between smoking and CRC is important in view of the high incidence of CRC in our country and the ever increasing number of smokers and in
view of smoking as a modifiable risk. These findings may be use in educating the public on
smoking cessation and also helping healthcare providers in screening patients in the high risk
group for early detection of CRC. It also provides us with more local data on which is still
very few and a role in future studies.
Keywords: Cigarette smoking, colorectal cancer, case-control study.
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