Antibiotic use and risk of gynecological cancer.

OBJECTIVES

Several studies addressed the association between antibiotic use and breast cancer risk. The objective of this study was to assess the association between antibiotic use and risk of cervical, ovarian, and uterine cancer.

STUDY DESIGN

We carried out a population-based case-control study using data from Saskatchewan Health administrative databases (Canada) between the years 1981 and 2000. Cases were matched to 4 controls, using incidence density sampling. The effect of dosage and timing of antibiotic use, over a minimum of 15 years before diagnosis, on cervical, ovarian, or uterine cancer risk was assessed. Number of prescriptions and number of pills were used as exposure definitions. The effect of different classes of antibiotics on cancer risk was also studied.

RESULTS

A total of 1225 cancer cases [192 cervical, 445 ovarian, and 588 uterine] and 4900 matched controls were included in this study. Antibiotic exposure (number of prescriptions) during the period of 1-15 years in the past was significantly associated with a reduced risk of cervical cancer; Relative Risk (RR)=0.40, 0.31, 0.26, and 0.29 for the four exposure quartiles, respectively. No association was found for ovarian or uterine cancer. When number of pills was considered, similar results were found. There was no effect of the timing or class of antibiotic exposure on cervical cancer risk.

CONCLUSIONS

Antibiotic exposure up to 15 years in the past was associated with a decreased risk of cervical cancer. The lack of temporal trends and the absence of class specific effects suggest a non-causal relationship.