Recent reports have shown that physical activity improves the outcome of patients with colorectal cancer as well as breast and prostate cancer.
However, the mechanisms whereby physical activity reduces cancer mortality are not well established.
Dr Haydon and colleagues from Australia identified incident cases of colorectal cancer in the Melbourne Collaborative Cohort Study.
This is a prospective cohort study of 41,528 Australians recruited from 1990 to 1994.
Information on tumor site and stage, treatments given, recurrences, and deaths were obtained from systematic review of the medical records.
The research team made baseline assessments of physical activity and body size.
Cases with available plasma had pre-diagnosis insulin-like growth factor 1 and insulin-like growth factor binding protein 3 levels measured.
The researchers assessed associations between these hormones and colorectal cancer specific deaths with respect to physical activity.
The team identified a total of 526 cases of colorectal cancer.
|Colorectal cancer deaths were reduced by 48%|
Of these, 443 had insulin-like growth factor 1 and insulin-like growth factor binding protein 3 levels measured.
Median follow up among survivors was 6 years.
For the physically active, increasing insulin-like growth factor binding protein 3 by 26.2 nmol/l was associated with a 48% reduction in colorectal cancer deaths.
The team observed no association for insulin-like growth factor 1.
For the physically inactive, neither insulin-like growth factor 1 and insulin-like growth factor binding protein 3 was associated with disease specific survival.
Dr Haydon's team concluded, “This study supports the hypothesis that the beneficial effects of physical activity in reducing colorectal cancer mortality may occur through interactions with the insulin-like growth factor axis and in particular and insulin-like growth factor binding protein 3.”