Bone mass density, subsequent risk of colon cancer and survival in postmenopausal women

Objectives To test the hypothesis that high bone mass density (BMD), a potential marker for cumulative exposure to endogenous estrogen, calcium and vitamin D intake, is associated with a lower risk of colon cancer, and that women with a lower BMD are likely to develop a more aggressive form of colon cancer, as defined by mortality. Study design and setting BMD was measured in three different sites (Ward's triangle, trochanter, femoral neck) in 1,471 women 60 years of age. All incident cases of colon cancers were identified through record-linkage of cancer registry. The women were followed for a mean of 9.5 years. Results Overall 31 cases of colon cancer were observed among 28.6 expected (standardized incidence ratio (SIR) = 1.09, 95% confidence interval: 0.79-1.25). The SIR decreased with increasing BMD showing a significantly decreasing risk of 20% for women who were at the higher BMD comparatively to women who were at the lower BMD in all the skeletal sites. The 10-year survival rates showed that survival was increasing with increased BMD, but not significantly. Conclusion The findings suggest that postmenopausal women with lower BMD have an increased risk of colon cancer. The biological mechanisms linking bone mass to colon cancer risk are not clear.