To the Editor: Dr Velicer and colleagues1 reported an association between use of antibiotics
and increased risk of breast cancer. We have several concerns about the design
of this study. First, because the authors did not obtain data about other
prescription medications, they could not establish that the effect was specifically
due to antibiotics. Second, although the regression analyses were adjusted
for age and duration of insurance enrollment, the authors apparently did not
adjust for other documented confounders, such as body mass index, family history
of breast cancer, and age at menarche. Third, other confounding factors that
might be correlated with both the need for antibiotics and the risk of breast
cancer were not analyzed (eg, smoke exposure, weight fluctuations, and use
of ethanol). Finally, the results are inconsistent with data from animal studies
that show no relationship between extended antibiotic exposure and breast
cancer.2 Until these issues are addressed
we believe that the judicious use of antibiotics is still safe in appropriate
patients regardless of the patient's individual risk of breast cancer.