Table 2.

Relative risk of breast cancer associated with >100 days of use of various antibiotics and antibiotic groups compared with no use

Antibiotic(s)Thousands of person-yearsNo. casesHR (95% CI)
Penicillins252.54681.03 (0.94-1.13)
Tetracyclines344.83931.23 (1.11-1.36)
Macrolides116.81451.16 (0.98-1.36)
Quinolones18.0340.76 (0.54-1.07)
Cephalosporins67.71310.92 (0.77-1.09)
Lincosamides4.480.79 (0.40-1.59)
Aminoglycosides*13.6*30*1.03 (0.72-1.47)*
Sulfonamides115.72231.03 (0.90-1.17)
Trimethoprim95.91680.94 (0.81-1.10)
Trimethoprim/sulfamethoxazole88.61550.97 (0.82-1.13)
Metronidazole4.780.97 (0.48-1.93)
Isoniazid62.4340.72 (0.51-1.00)
Rifampin5.170.83 (0.39-1.73)
Nitrofurantoin60.91210.92 (0.77-1.11)
  • NOTE: Controlled for hormone use.

  • * Findings for ≥11 days of use. There was only one case with ≥101 days of use. Most aminoglycoside administration is parenteral and not recorded in the PIMS records.