ASPO Abstracts
Ultraviolet radiation and breast cancer risk in a large prospective cohort
Category: Molecular Epidemiology & Environment
Conference Year: 2021
Abstract Body:
Purpose: We evaluated the association between residential levels of ultraviolet radiation (UV), a source of vitamin
D, and incident breast cancer in a large prospective cohort.
Methods: Using a spatiotemporal kriging model, we estimated residential UV exposure levels at the enrollment
addresses (2003-2009) of breast cancer-free women ages 35-74 years participating in the Sister Study and living
in the contiguous United States (N= 48,432). Cox proportional hazards models were used to estimate adjusted
hazard ratios (HRs) and 95% confidence intervals (95% CI) for the risk associated with an increase in UV
exposure levels (mW/m2) categorized in quintiles. We examined the association for breast cancer overall (invasive
and ductal carcinoma in situ) and stratifying by estrogen receptor (ER) status of the tumor. We considered effect
modification by regular (≥ 4 times/week) supplement (multivitamin or vitamin D) use.
Results: Over a mean of 10 years of follow up, 3,510 incident breast cancer diagnoses were reported. We found
no evidence of an association between living in areas with higher levels of UV radiation and overall breast cancer
risk (Quintile 5 vs Quintile 1 (Q5 vs. Q1), HR=1.00, 95% CI: 0.90, 1.11). Higher UV levels were inversely
associated with the risk of ER- breast cancer (Q5 vs Q1, HR=0.74, 95% CI: 0.55, 0.99), but not ER+ (Q5 vs Q1,
HR=1.04, 95% CI: 0.92, 1.18). For ER- breast cancer, the inverse association was more pronounced in women
who did not regularly take supplements (Q5 vs Q1, HR= 0.52, 95% CI: 0.28, 0.98) compared with those who did
regularly take supplements (Q5 vs Q1, HR=1.00, 95% CI: 0.66, 1.51; p-for-heterogeneity=0.05).
Conclusions: The findings from this study support a role for UV exposure and vitamin D in the etiology of ER-
breast cancer.
Keywords: Ultraviolet Radiation vitamin D