Cigarette smoking is a possible risk factor for colorectal cancer (CRC). However, long-term risk estimates among female smokers remain unclear.
In this study, researchers from the United States assessed cigarette smoking and CRC risk, both overall and by anatomic subsite, in postmenopausal women.
The team collected the data from a large population-based cohort (n = 41,836) of randomly selected women, aged 55 to 69 years.
They determined cigarette smoking and other CRC risk factors at baseline, in 1986.
|Women who have ever smoked have increased risks for incident and fatal colorectal cancers.|
|Clinical Gastroenterology and Hepatology|
The researchers then identified 869 incident and 249 fatal cases of CRC were identified through 1999.
The team calculated CRC risks using Cox proportional hazards regression models.
The researchers found that, compared with women who had never smoked, ever smokers had slightly increased risks for both incident (RR, 1.17) and fatal (RR, 1.31) CRC.
They also found that incident CRC risks increased progressively by lengthening induction period, reaching a 30% increase (RR, 1.30) after age 45 years.
When data was analyzed by anatomic subsite, ever smoked cigarettes and induction period were more strongly associated with incident proximal CRC, than incident distal CRC.
Dr Paul Limburg's team concluded, "In this long-term cohort study of postmenopausal women, cigarette smoking was positively associated with CRC risk".
"Onset of smoking in the distant past appeared to confer the greatest risk, especially for incident proximal CRC".
"These data support a potential subsite-specific role for cigarette smoking in colorectal carcinogenesis, at least among women".
"Based on emerging data, an epigenetic pathway for smoking-induced CRC is proposed".