Cancer registry data, analysis

In the beginning, before there is analysis, there must be accurate description. How much cancer is there, and how do rates of occurrence vary geographically, and between sexes, and with age How do rates of different types of cancer vary over time, and what happens to the rates that occur in specific groups of people when they move from one geographic location to another Information describing these types of differences and trends - which can be compiled with accuracy only when cancer registry information is reliable - are enormously beneficial in providing clues to the causes of cancer. The statistical data presented in Chapter 5 arose from these types of studies. 

In a case-control study in the north of Sweden, Hallquist et al. (1993) compared 188 men and women aged 20-70 years who had thyroid cancer with age- and sex-matched controls (two per case) selected from a register of the local population. The cases were identified retrospectively from a cancer registry and excluded a proportion of patients (19%) who had died by the time of the study. Exposure to potential risk factors, including chlorophenols, was ascertained by postal questionnaire with a supplementary telephone interview if answers were incomplete. The response rates for the cases and controls were 95% and 90%, respectively. Of the 171 cases analysed, 107 had papillary tumours. Four cases and three controls reported exposure to chlorophenols (odds ratio, 2.8 95% CI, 0.5-18). [The Working Group noted that the method of statistical analysis was not the most appropriate for individually matched data, but this is unlikely to have produced serious bias.]... 

Coal Tar Products. An excess of breast cancer cases in St. Louis Park, Minnesota, was tentatively associated with coal tar contamination of the water supply (Dean et al. 1988). However, in a subsequent analysis of these data, the Minnesota Department of Health (1985) concluded that this study did not provide adequate evidence to associate breast-cancer with coal tar creosote-contaminated water (for a detailed discussion of these data, see Section 3.2.2.7 Cancer). No adverse effects on sperm characteristics were reported in male workers exposed to coal tar pitch volatiles in an industrial setting (Ward 1988). In addition, no adverse reproductive outcomes were detected in a survey of inhabitants of a housing development built on an abandoned creosote factory site, which was known to be contaminated with creosote (Agency for Toxic Substances and Disease Registry 1994). A retrospective study of dermal exposure to coal tar found no increased risk of spontaneous abortion associated with exposure to coal tar during pregnancy, but this was a small study and was unlikely to have sufficient resolution to detect a modest increase in risk (Franssen et al. 1999). 

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