Cervical cancer screening in Canadian Native women. Adequacy of the Papanicolaou smear.

Cervical cancer mortality remains high in Canadian Native women in British Columbia. Underutilization of the Provincial Cytology Screening Program by Canadian Native women has been documented. Another potential factor is the quality of specimens obtained. Proportions of unsatisfactory smears and smears lacking endocervical cells, which reflect the sampling technique, were compared between Canadian Native and other British Columbian women. The findings suggest that differences in the quality of cytologic smears do not explain the observed discrepancy in cervical cancer mortality between Canadian Native and non-Native populations.

Reliability of dietary information from surrogate respondents.

A self-administered food frequency questionnaire was included as part of a case-control study of breast cancer in 1980-82. In 1986-87, a second food frequency questionnaire was sent to surviving cases and husbands of deceased cases; 30 spouses (86% response rate) and 263 surviving cases (88% response rate) returned questionnaires. The dietary questions concerned consumption of specific food items by the case before diagnosis of breast cancer. Missing values were less common in the second questionnaire; there was no significant difference in missing values between surviving cases and spouses of deceased cases. Kappa statistics comparing responses in the first and second questionnaires were significantly lower for spouses of deceased cases than for surviving cases. Reported level of confidence by the husbands regarding knowledge about their wives' eating habits did not influence the kappa statistics or the frequencies of missing values. The lack of good agreement has important implications for the use of proxy interviews from husbands in retrospective dietary studies.

The Screening Mammography Program of British Columbia: pilot study.

A government-funded pilot project of high volume screening mammography was conducted in Vancouver, British Columbia. 7,100 women were screened over a 9-month period, averaging 43 women per day at a cost of $33.81 per woman screened. 722 (10%) had abnormal mammograms; 144 received breast biopsies; and 29 were diagnosed with cancer. The overall cancer detection rate was 4.1 per 1,000 (0.8 and 4.8 for incident and prevalent cases, respectively). The staging distribution for the 29 cancer cases was 5, 15, 8 and 1 for in situ, stage I, II and III, respectively.

Mortality and cancer incidence in a cohort of commercial airline pilots.

We undertook a cohort study of all male pilots employed since January 1, 1950, by CP Air, now Canadian Airlines International. A total of 913 eligible pilots--630 active and 283 no longer employed--contributing 18,060 person-years of observation, were identified through company records. As of October 31, 1988, current status was obtained on 891 (97.6%). Standardized mortality ratio (SMR) and standardized incidence ratio (SIR) were used to compare, respectively, the mortality and cancer incidence of the cohort with that of the British Columbia population. Statistical significance of the SMR and SIR by comparison with the Poisson distribution (p less than 0.05 one-sided) and 90% confidence intervals (CI) were calculated. Excess deaths were observed for aircraft accidents (No. = 23; SMR = 21.29; p less than 0.001; CI 14.60, 30.20), brain cancer (No. = 4; SMR = 4.17, p = 0.017; CI 1.40, 9.50) and rectal cancer (No. = 3; SMR = 4.35; p = 0.033; CI 1.20, 11.20). Excess cancer incidence was noted for non-melanoma skin cancer (No. = 26; SIR = 1.59; p = 0.017; CI 1.10, 2.20), brain cancer (No. = 4; SIR = 3.45; p = 0.030; CI 1.20, 7.90) and Hodgkin's Disease (No. = 3; SIR = 4.54; p = 0.030; CI 1.20, 11.70). These findings, suggesting an excess risk for certain cancers in commercial airline pilots, are based on small numbers and need to be confirmed in larger cohort studies.

Differential misclassification bias and dietary recall for the distant past using a food frequency questionnaire.

Cases (n = 263) and controls (n = 200) returned self-administered food frequency questionnaires in 1980-1982 and again in 1986 as part of a case-control study of breast cancer. The questionnaire asked about consumption of specific food items as recalled for four different age periods. K-statistics comparing responses in the first and second questionnaires were generally similar for cases and controls and were consistent across the different age periods. The influence of recent dietary change on dietary recall diminished for the more distant past. The food frequency questionnaire was found to be more reliable for specific food items for the distant past than for the more recent past. Differential misclassification bias between cases and controls was less apparent for the more distant past. The frequency and interpretation of missing values is discussed.

Identification of occupational cancer risks using a population-based cancer registry.

The study of Xuan Wei fuel use and lung cancer mortality and also the interim case-control study suggested an association between domestic smoky coal use and Xuan Wei lung cancer. The collaborative studies of physical characterization, chemical analysis, and toxicology further substantiated this linkage. The Xuan Wei residents who used smoky coal inhaled extremely high concentrations of mostly submicron-sized particles, which can be inhaled and deposited effectively deep in the lung. These fine particles were composed mostly of organic compounds (72%), including mutagenic and carcinogenic organic compounds, especially in the aromatic and polar fractions. These residents were exposed to polycyclic aromatic compounds, such as benzo[a]pyrene, at comparable or higher levels than those measured in coke oven plants and other occupational environments (International Agency for Research on Cancer 1984). In comparison with wood and smokeless coal combustion emissions, the organic extracts of smoky coal emission particles showed much higher activity of genotoxicity and carcinogenicity. These results all point to a strong etiological link between the complex organic mixtures from smoky coal emissions and Xuan Wei lung cancer. This study and studies reported by other investigators (de Koning et al. 1984) suggested little association between indoor open-fire wood smoke and lung cancer. The less efficient lung deposition of the larger particles from wood combustion, as well as the lower concentrations of biologically active organic compounds, may contribute to the low rate of lung cancer in the wood-burning communes. As to the smokeless coal emissions, the lower particulate concentration and the lower organic content of the particles emitted may also contribute to the low lung cancer rate in the commune using this fuel. In conclusion, the complex organic mixtures from combustion emissions are genotoxic and carcinogenic in animal and in vitro assays. The magnitude of the cancer risks from the complex organic mixtures in man depends on the degree of the exposure, the types of the compounds contained in the mixtures, and the concentrations of these biologically active compounds present in the combustion emissions.