Frequent Antibiotics and Risk of Second Breast Cancers
This seems like an arcane but interesting article. I have read the abstract a couple of times and then skimmed the whole study, and, each time, have been left more or less scratching my head. It is always difficult not to personalize things we read, and I surely don't fit into this group of heavy antibiotic users who may have a slightly increased risk of developing a second breast cancer. Of course, if anyone actually knew why a woman develops breast cancer, we would be miles ahead.
This is a report from Seattle, and I give you the abstract. It surely is not a reason to become concerned if you are someone who frequently needs antibiotics. It is is just, I think, interesting.
Frequent Antibiotic Use and Second Breast Cancer Events
Heidi S. Wirtz1, Diana S.M. Buist3,4,5, Julie R. Gralow6, William E. Barlow2,7, Shelly Gray1, Jessica Chubak3,5, Onchee Yu5, Erin J.A. Bowles5, Monica Fujii5, and Denise M. Boudreau1,5
Background: Antibiotic use maybe associated with higher breast cancer risk and breast cancer mortality, but
no study has evaluated the relation between antibiotic use and second breast cancer events (SBCE).
Methods: We conducted a retrospective cohort study among women !18 years, diagnosed with incident
stage I/II breast cancer during 1990–2008. Antibiotic use and covariates were obtained from health plan
administrative databases and medical record review. Frequent antibiotic use was defined as !4 antibiotic
dispensings in any moving 12-month period after diagnosis. Our outcome was SBCE defined as recurrence or
second primary breast cancer. We used multivariable Cox proportional hazards models to estimate HR and
95% confidence intervals (CI), accounting for competing risks.
Results: A total of 4,216 women were followed for a median of 6.7 years. Forty percent were frequent
antibiotic users and 558 (13%) had an SBCE. Results are suggestive of a modest increased risk of SBCE (HR,
1.15; 95% CI, 0.88–1.50) among frequent antibiotic users compared with nonusers. Any potential increased
risk was not supported when we evaluated recent use and past use. We observed no dose–response trends
for SBCE with increasing duration of antibiotic use nor did we find evidence for altered SBCE risk in the antibiotic classes studied.
Conclusions: Frequent antibiotic use may be associated with modestly elevated risk of SBCEs, but the
association was not significant.
Impact: Additional investigation by antibiotic class and underlying indication are important next steps
given the high prevalence of frequent antibiotic use and growing number of breast cancer survivors.
Cancer Epidemiol Biomarkers Prev; 1–12. !2013 AACR.