A variety of cancer sites and exposures have been explored, with many investigations involving multi-disciplinary approaches to understanding biologic mechanisms of carcinogenesis. Of particular interest has been the relationship of exogenous hormones (menopausal estrogens and oral contraceptives) to risk of both breast and endometrial cancers, with several recent investigations focusing on the effects of the increasingly prescribed estrogen-progestin therapy. In addition, studies have addressed reasons for varying geographic breast cancer rates, including occupational and environmental agents. Taking advantage of recent improvements in detection methods for the human papillomaviruses, several studies have addressed the relationship of viral positivity to well- established cervical cancer risk factors. Several large prospective studies are also underway to assess the relationship of viral presence and persistence to subsequent disease risk. Cohort studies are also underway to assess subsequent disease risk among patients with cosmetic breast implants, prenatal exposure to diethylstilbestrol, different types of gynecologic operations, and various immunologic conditions (with specific attention given in the latter to relationships with diagnosis and treatment for rheumatoid arthritis). Two international studies of nasopharyngeal cancer have been undertaken, with an aim towards identifying factors which may enhance effects of the Epstein-Barr virus. Further, a multi-center study has addressed the relationship of water chlorination to various cancer sites. Time-trend analyses have been pursued for bladder, cervical, ovarian and vulvar cancers; tuberculosis; and non-Hodgkin's disease, with the latter analysis assessing relationships to outbreaks of chronic fatigue syndrome. Finally, of interest have been the occurrence of cancer in twins and several occupationally exposed cohorts, including aerial pesticide applicators and licensed radio amateurs.
