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We assessed the risk of occurrence of cancer associated with exposure to metronidazole in the 771 female residents of Rochester, Minnesota, who were treated with metronidazole for vaginal trichomoniasis during the period 1960 through 1969 and were followed up for a total of 12,628 person-years. Standardized morbidity and mortality ratios were determined by using an expected number calculated by applying age-specific incidence rates from Rochester studies and Cancer Surveillance, Epidemiology, and End-Results Reporting (SEER) data to the person-years of follow-up. The overall standardized morbidity ratios for cancer at all sites were 1.4 (Rochester, 1978 through 1983), 1.5 (SEER data for Iowa, 1978 through 1981), and 1.2 (SEER data for Connecticut, 1978 through 1981). By site of the cancers, the standardized morbidity ratios greater than unity were those for malignant lesions of the lung, breast, thyroid, bladder, brain, kidney, nasopharynx, and oral cavity, as well as for multiple myeloma and malignant melanoma; however, the only significantly elevated standardized morbidity ratio was that for bronchogenic carcinoma. After adjustment for smoking status, the standardized morbidity ratio for bronchogenic cancer was 2.5 (95% confidence interval of 1.3 to 4.4). The standardized mortality ratio for cancer at all sites was 1.4 (95% confidence interval of 0.9 to 2.2). The analysis of these data suggests no significant increase in cancer-related morbidity or mortality for women exposed to metronidazole for treatment of vaginal trichomoniasis.

Reports in the popular press have suggested that exposure to diethylstilbestrol (DES) is followed by an abnormally high incidence of breast cancer. The reports were based on a reanalysis of data not considered ominous originally; and both data and analyses are summarized here. In addition, new data are presented on mothers of young women enrolled in the National DESAD Project at its Mayo Clinic Center. Among 408 women given DES, there were 8 confirmed instances of breast cancer, in comparison with an expected number of 8.1, based on breast cancer incidence rates among parous women in the local population. A previous case-control study of the possible association of antihypertensive therapy and breast cancer in the local population revealed DES exposure in 10% of the breast cancer group and 12% of the controls. These apparently negative results clearly indicate a need of further studies of the alleged effect of DES.

The 1,250 Mayo Clinic obstetric deliveries for 1976 were reviewed and 73 elective inductions were identified. Sixty-three of these mothers were successfully matched by gravidity, parity, and age within 5 years with healthy women in whom delivery was spontaneous at term. The mean birth weight for the electively delivered infants was greater than that for the controls, but the difference was not statistically significant. Mean gestation and 1-minute Apgar scores were similar for both groups. The neonatal problems observed, with the exception of elevated bilirubin levels, did not seem to point to any special hazard of induction. Even though pregnancy is interrupted, elective induction, as practiced at the Mayo Clinic, was not shown to produce a systematic reduction in birth weight.