ALBUQUERQUE – Postmenopausal women who reported a history of nonmelanoma skin cancer were almost 16% more likely to sustain a lower arm fracture than were women without a skin cancer history, according to a large, prospective, longitudinal study.
Women with prior nonmelanoma skin cancers (NMSCs) also were more likely to suffer a subsequent hip fracture, although the association did not reach statistical significance, said Eric Anderson of the dermatology department at Stanford (Calif.) University School of Medicine.
"These results suggest that prior history of NMSC is associated with an increased risk of subsequent bone fracture, contrary to our hypothesis," noted Mr. Anderson. He presented the findings at the annual meeting of the Society for Investigational Dermatology.
Nonmelanoma skin cancer has been correlated with decreased fracture risk in at least one small cohort study, Mr. Anderson said (Osteoporos. Int. 2007;18:687-92). However, patients with NMSC also have been shown to wear more sunscreen and limit their sun exposure after diagnosis, which might lower their vitamin D levels and increase their fracture risk, Mr. Anderson noted (Cancer Causes Control 2012;23:133-40).
To better clarify the relationship between NMSC and fracture risk, Mr. Anderson and his associates compared prospective data from 4,289 women with self-reported NMSC and 67,470 women who did not report a history of NMSC at baseline. The participants were from the Womens Health Initiative, a prospective longitudinal cohort study of postmenopausal women aged 50-79 years who were enrolled at 40 centers in the United States. Participants were followed for more than 10 years, and new spine, hip, and lower arm fractures were recorded, Mr. Anderson said.
In age-adjusted Cox proportional hazards models, women with a history of NMSC were 1.55 times more likely to sustain a hip fracture (95% confidence interval, 1.31-1.85; P < 0.0001), 1.29 times more likely to suffer a spine fracture (95% CI, 1.10-1.51; P = 0.0018), and 1.28 times more likely to sustain a lower arm fracture (95% CI, 1.13-1.45; P < 0.0001) than were women who did not report a history of NMSC at baseline, Mr. Anderson and his associates reported.
After adjusting for sun exposure, sunscreen use, vitamin D intake, physical activity, and other risk factors for fracture, only lower arm fracture remained statistically significant (hazard ratio, 1.16; 95% CI, 1.31-1.85; P = 0.02), although hip fracture was borderline significant (HR, 1.18; 95% CI, 0.99-1.41; P = 0.06), the investigators reported. Baseline hip bone marrow density was not associated with risk of NMSC in a subgroup analysis of 4,267 women with available data, Mr. Anderson said.
"We’re inclined to believe that this increased fracture risk may be due to sun exposure avoidance after NMSC diagnosis," said Mr. Anderson. He added that, in future studies, the investigators would compare serum vitamin D levels between participants with and without a history of NMSC, and explore temporal relationships between diagnosis of NMSC and fracture occurrence.
The National Institutes of Health and the Medical Scholars Research Program at Stanford University funded the research. Mr. Anderson reported no conflicts of interest.