A case-control study of risk factors for sarcomas of the uterus. The World Health Organization Collaborative Study of Neoplasia and Steroid Contraceptives.

Using data collected as part of the hospital-based World Health Organization (WHO) Collaborative Study of Neoplasia and Steroid Contraceptives, the authors examined potential risk factors for sarcoma of the uterus. Twenty-nine patients with uterine sarcoma who were between 15 and 56 years of age and diagnosed at one of nine centers were matched on age and center to 198 controls selected from hospital admissions to other than obstetric and gynecologic wards. All women were interviewed regarding their medical and reproductive history, methods of birth control, and history of sexual relationships and of sexually transmitted infections. The risk of uterine sarcoma was lower in parous women compared to nulliparous women (odds ratio [OR] = 0.6; 95% confidence interval [CI] = 0.1, 3.3), and the risk decreased with increasing number of live births. A greater proportion of cases than controls reported giving birth to their first child at the age of 25 or later, even after adjustment for parity (OR = 3.5; 95% CI = 1.2, 10.9). Cases were also more likely than controls to report a history of a spontaneous abortion (OR = 2.5; 95% CI = 0.8, 7.4) or an induced abortion (OR = 1.6; 95% CI = 0.4, 6.3). Late menarche and early menopause were both positively associated with the risk of uterine sarcoma. No association was observed with a history of infertility, use of oral contraceptives, or measures of sexual activity. The findings with respect to childbearing and menstrual history differ from those of a recent cohort study, and indicate the need for larger investigations to assess the role of these and other risk factors in the occurrence of sarcomas of the uterus.