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.