Purpose: Bisphosphonates are used for the treatment of bone metastases and have been associated with a lower risk of breast cancer. A recent case-control study showed an inverse association between bisphosphonate use and colorectal cancer. Data from prospective cohorts are lacking.
Patients and methods: We prospectively examined the relationship between bisphosphonate use and risk of colorectal cancer among 86,277 women enrolled onto the Nurses Health Study (NHS). Since 1998, participants have returned biennial questionnaires in which they were specifically queried about the regular use of bisphosphonates. We used Cox proportional hazards models to calculate hazard ratios (HRs) and 95% CIs for risk of colorectal cancer.
Results: Through 2008, we documented 801 cases of colorectal cancer over 814,406 person-years of follow-up. The age-adjusted HR for women who regularly used bisphosphonates was 0.92 (95% CI, 0.73 to 1.14) and was further attenuated after adjustment for other risk factors (multivariate HR, 1.04; 95% CI, 0.82 to 1.33). The risk was not influenced by duration of use (P(trend) = 0.79). Compared with nonusers, the multivariate-adjusted HRs of colorectal cancer were 1.24 (95% CI, 0.94 to 1.64) for women with 1 to 2 years of use, 1.16 (95% CI, 0.79 to 1.69) for 3 to 4 years of use, and 0.97 (95% CI, 0.60 to 1.56) for ≥ 5 years of use. There was no association between bisphosphonate use and colorectal cancer within strata of other risk factors.
Conclusion: In a large prospective cohort, we did not observe an association between long-term use of bisphosphonates and risk of colorectal cancer.