Gerry B. Hill

Is Occupation a Risk Factor for Thyroid Cancer

A Canadian case-control study explored the etiology of thyroid cancer, including occupational exposure. Analysis of job history from 1272 thyroid cancer patients and 2666 controls revealed statistically significant risks among the following occupations: Wood Processing, Pulp and Papermaking (odds ratio [OR] = 2.54, 95% confidence interval [CI] = 1.11-5.83); Sales and Service (OR = 1.26, 95% CI = 1.05-1.52); and Clerical (OR = 0.81, 95% CI = 0.67-0.97). ORs were adjusted for age, sex, province, cigarette smoking, education, self-reported exposure to radiation at work, and duration of employment. Exposure to ionizing radiation or electromagnetic fields at work (inferred from job histories) did not affect risk, nor did socioeconomic status, measured by education, income, or occupational prestige. Possible explanations for the results and further investigations are discussed.

the Latency Period of Carcinoma-in-situ of the Cervix

The age-specific incidence figures for gonorrhea and cervical carcinoma-in-situ in Alberta, Canada, have been correlated. The findings suggest that when reliable population-based data are available, changes in incidence and age distribution for gonorrhea can be regarded as predictive for comparable changes in incidence and age distribution for carcinoma-in-situ of the cervix with a delay in presentation of approximately five years. The latency period of carcinoma-in-situ of the cervix does not seem to vary considerably among different age groups. The results of the present study support the theory that a sexually transmitted infectious agent could be an etiologic factor in cervical cancer. Because gonorrhea rates in younger women indicate that they are engaging in earlier sexual activity with more partners, regular cervical screening should be encouraged to prevent a potential major increase of invasive cervical cancer.

Trends in the incidence of cancer of the female breast and reproductive tract in Alberta, 1953 to 1977.

A log-linear model was used to separate age, secular, and cohort trends in the incidence of cancer of the breast, ovary, corpus uteri, cervix uteri, vagina, and vulva in female residents in Alberta over the period 1953 to 1977. The age trends are similar for each cancer site increasing sharply in the premenopausal period and then leveling off. In the case of breast cancer, a point of inflection at the menopause (Clemmesens hook) persists. A gradually increasing secular trend in incidence was evident for all sites except cervix uteri, the incidence of which declined after 1960. Cyclical cohort trends were found for cancers of the breast, ovary, and corpus uteri, inversely correlated with early fertility. The cohort trends for cervix uteri, vagina, and vulva increased sharply for cohorts born after 1940.