Cohort cancer incidence among pulp and paper mill workers in British Columbia

OBJECTIVES

A study was conducted to investigate cancer risks in a cohort of pulp and paper workers.

METHODS

All male workers with > or =1 years of employment in 14 pulp and paper mills in 1950-1992 were studied. Standardized incidence ratios (SIR) were used to compare the cancer incidence of the cohort with that of the Canadian male population. Record linkage with the National Cancer Registry was performed using the generalized iterative record linkage method.

RESULTS

Altogether 1756 cancer cases were observed in the entire cohort. For > or =15 years of work, the entire cohort had significantly increased SIR values for pleural and prostate cancer and skin melanoma; there was also a significantly increased risk for skin melanoma among workers in the kraft process only, rectal cancer among workers in the sulfite process only, and stomach and prostate cancer and all leukemias combined among workers in both the kraft and sulfite processes. A separate analysis comparing workers in pulping and papermaking with those in the pulping process only did not reveal any difference in cancer risk and hence did not modify the results. The SIR values for skin melanoma were not significantly increased in a comparison using the British Columbia male population. Nine of 10 pleural cancers were mesotheliomas, which likely reflect past asbestos exposure.

CONCLUSIONS

The results suggest that long-term work in the pulp and paper industry is associated with excess risks of prostate and stomach cancers and all leukemias for work in both kraft and sulfite processes and of rectal cancer for work in the sulfite process only.

First analysis of cancer incidence and occupational radiation exposure based on the National Dose Registry of Canada

A cohort study was conducted to investigate the relation between cancer incidence and occupational exposure to ionizing radiation. Records containing dose information from 1951 to 1988 for 191,333 persons were extracted from the National Dose Registry of Canada. The records were linked to the Canadian Cancer Data Base, with incidence data from 1969 to 1988. Standardized incidence ratios were calculated using Canadian cancer incidence rates stratified by age, sex, and calendar year. Excess relative risks were obtained from internally based dose-response analyses. The following significant results were found for males and females combined: a deficit in the standardized incidence ratio for all cancers combined; elevated standardized incidence ratios for thyroid cancer and melanoma; and elevated excess relative risks for rectum, leukemia, lung, all cancers combined, all except lung, and all except leukemia. For males, cancers of the colon, pancreas, and testis also showed significantly elevated excess relative risks. The specific cancer types listed above have been implicated in previous studies on occupational exposure to ionizing radiation, except for testis, colon, and melanoma, while the findings on thyroid cancer from previous studies are inconclusive. The thyroid standardized incidence ratios in this study are highly significant, but further investigation is needed to assess the possibility of association with occupational radiation exposure.

Identification of occupational cancer risks in British Columbia. A population-based case-control study of 995 incident breast cancer cases by menopausal status, controlling for confounding factors

Lifetime occupational histories as well as information on known and suspected breast cancer risk factors were collected by means of a self-administered questionnaire from 1018 women with incident breast cancer ascertained from the British Columbia Cancer Registry, and from 1020 population controls. A matched case-control study design was used. Conditional logistic regression for matched sets data and the likelihood ratio were used in a two-step procedure and were performed separately for pre-menopausal women, post-menopausal women, and for all cases combined. Excess risk was noted for several white-collar occupations. Significantly increased risk was observed: (1) among pre-menopausal women: in electronic data-processing operators; barbers and hairdressers; in sales and material processing occupations; and in the food, clothing, chemical and transportation industries; (2) among post-menopausal women: in schoolteaching; in medicine, health, and nursing occupations; in laundry and dry-cleaning occupations; and in the aircraft and automotive, including gasoline service station, industries. Several significant associations were also seen in the combined group of pre- and post-menopausal women, particularly in crop farmers and in the fruit and vegetable, publishing and printing, and motor vehicle repair industries. The results of this study suggest excess breast cancer risk in a number of occupations and industries, notably those that entail exposure to solvents and pesticides.

Identification of occupational cancer risks in British Columbia. Part II: A population-based case-control study of 1516 Prostatic cancer cases

We have, as part of a program aimed at detecting occupational risk factors in British Columbia, collected lifetime occupational histories from 15,643 incident cancer cases, of whom 1519 had a diagnosis of prostate cancer. Occupational risks for this cancer site are examined using this large data set, and the results are presented in this report.

Identification of occupational cancer risks in British Columbia. Part I: Methodology, descriptive results, and analysis of cancer risks, by cigarette smoking categories of 15,463 incident cancer cases

To identify occupational cancer risk factors, lifetime occupational, smoking, and alcohol-consumption histories were collected by means of a self-administered questionnaire from 15,463 male cancer patients aged 20 years and over as ascertained from the British Columbia population-based cancer registry; all cases were histologically confirmed. The study methodology, descriptive results, and cancer risks from cigarette smoking are reported. Assessment of questionnaire validation and reliability showed very high correlations between all variables analysed. Non-response bias, assessed among 221 non-responders and 432 matched controls, revealed no statistically significant differences for smoking status, education, or for 11 usual (longest-held job) occupational groups, except for managerial occupations and for four pooled groups that represented 6.7% of all occupations. Except for pancreatic cancer, a significant relationship was found for all cancer sites known to be strongly associated with cigarette smoking.

Occupational risk factors for prostate cancer mortality in British Columbia, Canada

BACKGROUND

Although prostate cancer is the most common life-threatening cancer among males in North America, relatively little is known about its etiology. We have conducted a proportional mortality study to generate hypotheses concerning occupational risk factors for the disease.

METHODS

Age standardized proportional mortality ratios (PMR) for prostate cancer were calculated for a total of 216 occupations and 88 industries. Separate calculations were done for all male deaths age 20 and up and for deaths that occurred during men's working lifetime (age 20-65).

RESULTS

Elevated mortality from prostate cancer was seen among business owners and managers (PMR = 110; 95% CI = 101-118), brokers (PMR = 184; 95% CI = 122-266), farmers and farm managers (PMR = 112; 95% CI = 105-120), and school teachers (PMR = 133; 95% CI = 101-174). Evaluation by industry shows elevated prostate cancer mortality in agriculture (PMR = 110; 95% CI = 103-118), financial institutions (PMR = 138, 95% CI = 112-170), and transportation equipment manufacture (PMR = 136; 95% CI = 109-168).

CONCLUSIONS

The findings suggest that workers in a number of occupations have elevated risks of prostate cancer including farmers and teachers. More detailed cohort and case-control studies, evaluating specific exposures are required before primary prevention programs in the workplace are feasible.

First analysis of mortality and occupational radiation exposure based on the National Dose Registry of Canada

A cohort mortality study of occupational radiation exposure was conducted using the records of the National Dose Registry of Canada. The cohort consisted of 206,620 individuals monitored for radiation exposure between 1951 and 1983 with mortality follow-up through December 31, 1987. A total of 5,426 deaths were identified by computerized record linkage with the Canadian Mortality Data Base. The standardized mortality ratio for all causes of death was 0.61 for both sexes combined. However, trends of increasing mortality with cumulative exposure to whole body radiation were noted for all causes of death in both males and females. In males, cancer mortality appeared to increase with cumulative exposure to radiation, without any clear relation to specific cancers. Unexplained trends of increasing mortality due to cardiovascular diseases (males and females) and accidents (males only) were also noted. The excess relative risk for both sexes, estimated to be 3.0% per 10 mSv (90% confidence interval 1.1-4.8) for all cancers combined, is within the range of risk estimates previously reported in the literature.

Reducing cervical cancer among First Nations women

First Nations women in British Columbia have a four to six times higher mortality rate from cancer of the cervix than do women in the general population. Their participation in the provincial Cervical Cytology Screening Program (CCSP) is less regular and less frequent than other women in B.C. Likewise, they have more difficulty in obtaining culturally suitable health care services from respectful and consistent professionals. These issues should be of critical concern to nurses, as nurses provide the majority of health services to First Nations people.

Cohort mortality study of pulp and paper mill workers in British Columbia, Canada

The authors studied a cohort of 30,157 male pulp and paper workers in British Columbia, Canada. Of these, 20,373 worked in kraft mills only, 5,249 in sulfite mills only, and 4,535 in both kraft and sulfite mills. All workers with at least 1 year of employment on January 1, 1950, or thereafter until December 31, 1992, were studied. Standardized mortality ratios (SMRs) were used to compare the mortality rates of the cohort with those of the Canadian male population. Ninety percent confidence intervals (CIs) for the SMRs were obtained. Cancer risks significantly associated with work duration and time from first employment of 15 years or more were observed: 1) total cohort: pleura (SMR = 3.61, 90% CI 1.42-7.58); kidney (SMR = 1.69, 90% CI 1.13-2.43); brain (SMR = 1.51, 90% CI 1.03-2.16); 2) workers in kraft mills only: kidney (SMR = 1.92, 90% CI 1.04-3.26); 3) workers in sulfite mills only: Hodgkin's disease (SMR = 4.79, 90% CI 1.29-12.37); 4) workers ever employed in both kraft and sulfite mills: esophagus (SMR = 1.91, 90% CI 1.00-3.33). These malignancies have been associated with the following known or suspected carcinogens to which pulp and paper workers may have been exposed: asbestos (pleura), biocides (kidney), formaldehyde (kidney, brain, Hodgkin's disease), hypochlorite (esophagus). A nested case-control study with detailed exposure assessment is under way to help determine whether excess risks for specific cancers reflect exposure among subsets of workers.

Cervical cytology screening. How can we improve rates among First Nations women in urban British Columbia?

OBJECTIVE

To determine Pap smear screening rates among urban First Nations women in British Columbia; to identify facilitators and barriers; and to develop, implement, and evaluate specific interventions to improve Pap smear screening in Vancouver.

DESIGN

Computer records of band membership lists and the Cervical Cytology Screening Program registry were compared to determine screening rates; personal interviews and community meetings identified facilitators and barriers to urban screening programs. A community advisory committee and the project team collaborated on developing specific interventions.

SETTING AND PARTICIPANTS

Purposive sample of British Columbia First Nations women, focusing on women living in Vancouver.

INTERVENTIONS

Poster, art card, and follow-up pamphlet campaign; articles in First Nations community papers; community meetings; and Pap smear screening clinics for First Nations women.

MAIN OUTCOME MEASURES

Pap smear screening rates among BC First Nations women according to residence and reasons for not receiving Pap smears.

RESULTS

Pap smear screening rates were substantially lower among First Nations women than among other British Columbia women; older women had even lower rates. No clear differences were found among First Nations women residing on reserves, residing in Vancouver, or residing off reserves elsewhere in British Columbia. Facilitators and barriers to screening were similar among women residing on reserves and in Vancouver. Many First Nations women are greatly affected by health care providers' attitudes, abilities to provide clear information, and abilities to establish trusting relationships.

CONCLUSIONS

Family physicians are an important source of information and motivation for Pap smear screening among First Nations women.

Cohort study of Air Canada pilots: mortality, cancer incidence, and leukemia risk

Despite the special working environment and exposures of airline pilots, data on risk of death and cancer incidence in this occupational group are limited. The authors investigated a cohort of 2,740 Air Canada pilots who contributed 62,449 person-years of observation. All male pilots employed for at least 1 year on and since January 1, 1950, were studied. The cutoff date for outcome information was December 31, 1992. Standardized mortality ratio (SMR) and standardized incidence ratio (SIR) were used to compare mortality rates and cancer incidence rates of the cohort with the respective Canadian population rates. Ninety percent confidence intervals of the SMR and SIR were calculated. Statistically significant decreased mortality was observed for all causes (SMR = 0.63, 90% confidence interval (CI) 0.56-0.70), for all cancers (SMR = 0.61, 90% CI 0.48-0.76), and for all noncancer diseases (SMR = 0.53, 90% CI 0.45-0.62). Mortality from aircraft accidents was significantly raised (SMR = 26.57, 90% CI 19.3-35.9). Significantly decreased cancer incidence was observed for all cancers (SIR = 0.71, 90% CI 0.61-0.82), rectal cancer (SIR = 0.42, 90% CI 0.14-0.96), lung cancer (SIR = 0.28, 90% CI 0.16-0.46), and bladder cancer (SIR = 0.36, 90% CI 0.12-0.82). Prostate cancer (SIR = 1.87, 90% CI 1.38-2.49) and acute myeloid leukemia (SIR = 4.72, 90% CI 2.05-9.31) were significantly increased. The preferred relative risk model for radiation-induced nonchronic lymphoid leukemia (Beir V report) was applied to the cohort by using published estimates of in-flight radiation exposures. The estimated relative risk ranged from 1.001 to 1.06 and did not differ significantly from the observed SIR (SIR = 1.88, 90% CI 0.80-3.53). However, the incidence rate of acute myeloid leukemia was significantly increased. Monitoring of in-flight radiation exposure and long-term follow-up of civil aviation crew members is needed to further assess cancer incidence and leukemia risk in this special occupational group.

Human pharmacokinetic study of immediate-release (codeine phosphate) and sustained-release (codeine Contin) codeine

The authors compared, in a double-blind, randomized, crossover study in 13 healthy adult volunteers, the single- and multiple-dose pharmacokinetics, relative bioavailability, and side effects of a new oral sustained-release formulation of codeine (SRC) containing 150 mg codeine base, with oral immediate-release codeine phosphate (IRC). Sustained-release codeine was given at a dose of 150 mg every 12 hours for 5 doses; IRC was given at a dose of 60 mg (2 x 30 mg) every 4 hours for the first 3 doses, and 30 mg every 4 hours thereafter for 12 doses. Plasma codeine levels were determined using a sensitive and specific high-performance liquid chromatography method and corrected for dose administered and codeine base equivalent. Mean values for single-dose pharmacokinetic parameters for SRC and IRC, respectively, were: Cmax of 217.8 and 138.8 ng/mL; Tmax of 2.3 and 1.1 hours; AUC0-inf of 1202.3 and 1262.4 ng.mL-1.hour-1; and t1/2el of 2.6 hours for both formulations. Their respective mean steady-state pharmacokinetic parameters were: Cmax of 263.8 and 222.9 ng/mL; Tmax of 3.2 and 1.1 hours; AUC0-12h of 1576.4 and 1379.1 ng.mL-1.hour-1; and t1/2el of 2.8 and 2.3 hours. These results indicate comparable bioavailability between both formulations with SRC providing delayed peak plasma levels. The sustained-release character of SRC can be explained by a delayed absorption, which is not limiting to drug elimination. Sustained-release codeine provides higher plasma codeine levels over a broader time interval and is expected to improve pain management.

Mortality among female registered nurses and school teachers in British Columbia

The mortality profile of female nurses and teachers in British Columbia (BC) was examined using age-standardized proportional mortality ratios (PMRs) calculated for the period 1950-1984. Lowered overall mortality among nurses was seen for degenerative heart disease and for cerebrovascular accidents. Significantly elevated PMR values were observed for cancer of the breast and ovary in nurses of age 20-65 years. PMRs were significantly elevated for cancer of the pancreas and leukemia among those age 20 years and older. Elevated values were also observed for motor vehicle accidents and suicide among nurses in both age groups. Lower than expected mortality from degenerative heart disease and cerebrovascular accidents was seen in working age teachers (age 20-65 years). However, elevated PMRs were detected for carcinoma of the colon, breast, endometrium, brain, and melanoma. Among those 20 years and over, significantly elevated PMRs were also observed for cancers of the ovary and other digestive organs. Elevated PMRs were found for motor vehicle and aircraft accidents. Mortality from cirrhosis of the liver was lower than anticipated in both teachers and nurses. A number of significant PMRs declined when deaths of "homemakers" were withdrawn from the comparison group used to generate PMR values, suggesting that risk of death from various causes among women working outside the home differ from those seen in women who are predominantly in the home.

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.

History of lactation and breast cancer risk

A self-administered questionnaire was completed by 1,018 women diagnosed with breast cancer during 1988-1989 identified through the British Columbia Cancer Registry and by 1,025 controls selected at random from the Provincial Voters List. Parous premenopausal women who had never nursed (odds ratio (OR) = 1.3, 95% confidence interval (CI) 0.9-2.0) or who had lactated for 1 month or less (OR = 1.8, 95% CI 1.3-2.5) had an increased risk of breast cancer adjusted for age and parity, compared with women who had breast-fed 2 months or longer. The risk was particularly elevated (OR = 3.0, 95% CI 1.6-5.4) among women who reported having tried to nurse, but who were unsuccessful. Among women who nursed for at least 2 months, there was an indication of decreasing risk with increasing duration of nursing. Among postmenopausal parous women, no relation between lactation history and breast cancer risk was evident.

Rate of death from cervical cancer among native Indian women in British Columbia

OBJECTIVE

To compare the rates of death from cervical cancer among native Indian women and non-native women in British Columbia from 1953 to 1984.

DESIGN

Retrospective analysis of data retrieved from the British Columbia Division of Vital Statistics.

MAIN OUTCOME MEASURES

Age-standardized death rate and relative rate.

RESULTS

The rate of death from cervical cancer was significantly higher among the native women than among the non-native women throughout the study period. No deaths from cervical cancer were recorded in women under 20 years of age. Among those 20 to 64 the relative rate increased from 3.83 in 1953-62 to 6.53 in 1973-84; among those 65 or more it decreased slightly. For the entire study period the relative rate for women 20 to 64 years old was 5.95 and for those 65 or older 2.98.

CONCLUSION

The rate of death from cervical cancer among native women in British Columbia is unacceptably high, probably because the provincial screening program does not reach as many native women as it does non-native women.

The evaluation of analgesic effects in cancer patients as exemplified by a double-blind, crossover study of immediate-release versus controlled-release morphine

We compared the effects of controlled-release and immediate-release morphine preparations in adult patients with moderate-to-severe cancer pain and report methodologic approaches to pain evaluation. The study consisted of a two-phase randomized crossover trial preceded by a titration phase; all phases were conducted under double-blind conditions. To evaluate pain intensity, a visual analogue scale (VAS) and the Present Pain Intensity scale of the McGill Pain Questionnaire were used. Additional morphine solution for breakthrough pain was used as an outcome measure. Pain was evaluated nine times daily, which permitted correlation of pain scores with the pharmacokinetic patterns of the test drugs. Side effects were rated once daily, using a scale from 0 to 3. To assess the relative importance of side effects, a toxicity index was designed based on both the intensity and duration of each side effect. The overall VAS pain scores during treatment with controlled-release and immediate-release morphine were 1.3 (SD = 0.1) and 1.4 (SD = 0.2), respectively. Use of supplemental morphine solution for breakthrough pain expressed as the percentage of the daily dose of the test drug was 5.5% for the controlled-release drug and 10.9% for the immediate-release drug. Differences in pain scores, side effects, and supplemental morphine requirement between the two groups were not significant. We discuss methodologic issues in double-blind clinical trials of analgesics, in particular the validity of "Patient Preference" as an outcome measure and problems related to the titration phase.

Noncontraceptive hormone use and risk of breast cancer

All British Columbia (Canada) women under 75 years of age who were diagnosed with breast cancer during 1988-89 were asked to complete a postal questionnaire which included detailed information on menopausal estrogen use. Controls were drawn from the Provincial Voters List, matched by five-year age category to the cases. The present analysis consists of 699 cases and 685 controls who were postmenopausal due to natural causes or to a hysterectomy. There was no overall increase in risk of breast cancer associated with ever-use of unopposed estrogen (odds ratio [OR] = 1.0, 95 percent confidence interval [CI] = 0.8-1.3). For estrogen use of 10 years or longer, the relative risk [RR] was 1.6 (CI = 1.1-2.5). The risk estimate for current users was somewhat elevated (OR = 1.4, CI = 1.0-2.0). Compared with women who never used hormone preparations, women who had used estrogen plus progestogen had an RR of 1.2 (CI = 0.6-2.2). Our results suggest that ever-use of estrogen, with or without progestogen, does not appreciably increase the risk of breast cancer. However, long-term and recent use of unopposed estrogen may be associated with a moderately increased risk.

Efficacy of weekly cisplatin-based chemotherapy in recurrent and metastatic head and neck cancer

After disease recurrence or dissemination, patients who had been treated previously with radiation with or without surgery for cancer of the head and neck were given either cisplatin (16 patients), cisplatin/etoposide (15 patients), or cisplatin/etoposide/5-fluorouracil (5-FU) (19 patients) in an ambulatory care clinic. Intravenous (i.v.) cisplatin 25 mg/m2 was given weekly, while etoposide was given i.v. (80 mg/m2) on day 1 and orally (160 mg/m2) on day 2 of every odd-numbered week. In the three-drug regimen, 5-FU 500 mg/m2 i.v. was given every even-numbered week. Patients in all three groups received daily oral prednisone to decrease myelosuppression and oral co-trimoxazole and ketoconazole to prevent infection. The supportive drugs were given to all groups to keep these variables constant. As expected, myelosuppression did not occur in the cisplatin group, while the rates of severe neutropenia (less than 1.0 x 10(9)/L) in the two- and three-drug groups were 26% and 74%, respectively. The incidence of infection requiring hospitalization was low (2.5%). The response rate (complete plus partial) was lowest in the cisplatin group (6%) and higher in the cisplatin/etoposide (47%) and cisplatin/etoposide/5-FU (53%) groups. Because of the low response rate and the short time to progression (5 weeks) in the cisplatin group, 9 of these 16 patients were treated subsequently with cisplatin/etoposide. Time to progression and response duration were similar in the cisplatin/etoposide and cisplatin/etoposide/5-FU groups--12 and 14 weeks, and 12 and 9 weeks, respectively. Median survival times of the cisplatin and cisplatin/etoposide/5-FU groups were 36 and 34 weeks, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of recurrent and metastatic head and neck cancer with cisplatin/etoposide/bleomycin

Cisplatin/etoposide/bleomycin (DEB) was given as an outpatient regimen in a novel weekly schedule to 27 patients with recurrent and/or widely metastatic cancer of the head and neck region. Six of these patients also received mitomycin (DEB/M) when their disease failed to respond after at least three weekly DEB doses. All but three patients had been treated previously with radiotherapy directed to the primary site and regional nodal disease; four had also received chemotherapy with cisplatin or carboplatin. Before treatment with DEB, 19 patients had distant metastases. Of an intended 12 doses per patient, a mean of 8.2 was achieved. Myelosuppression was the major toxicity, with neutropenia in 45% of patients and significant anemia in 26%. The overall response rate to DEB in 27 patients was 59%, increasing to 70% after the addition of mitomycin. There were two complete and 17 partial responses. The median duration of response was 12 weeks and median survival was 6 months, with 20% of patients surviving 1 year. We conclude that the relatively short survival time together with the significant toxicity of the DEB/M regimen does not warrant its routine use in clinical practice. However, this regimen, or one patterned on it, should be evaluated in combination with radiotherapy as the initial treatment for selected patients with previously untreated head and neck cancer.

Mortality patterns in female domestic workers

To investigate mortality patterns for domestic workers, proportional mortality ratios (PMRs) were calculated for the 1,382 female domestic workers who died in British Columbia at age 20 years or over between 1950 and 1984. This group experienced fewer deaths than expected from cerebrovascular accidents (PMR = 84) and hypertension (PMR = 39). The proportion of deaths from cirrhosis was higher than expected (PMR = 152). An excess of observed deaths was also noted for all accidents (PMR = 126), accidents due to environmental factors (PMR = 439), and homicide (PMR = 235). Mortality from pneumonia was elevated for domestic workers aged 20 to 65 (PMR = 180). Further studies using more sophisticated epidemiologic methods are necessary to evaluate whether these deaths are a result of occupational exposures or of poor socioeconomic conditions.

Mortality and cancer incidence in aluminum reduction plant workers

An historical cohort study was conducted among 4,213 men who worked for 5 or more years at a Soderberg aluminum reduction plant in British Columbia (BC), Canada. Standardized mortality and incidence ratios were used to compare the mortality and cancer incidence of the cohort with that of the BC population and to examine risk by cumulative exposure to coal-tar pitch volatiles (CTPV) and electromagnetic fields. Significantly elevated rates were observed for bladder cancer incidence (standardized incidence ratio [SIR] = 1.69) and brain cancer mortality (standardized mortality ratio = 2.17). The risk of bladder cancer was strongly related to cumulative exposure to CTPV (P less than .01). The risk for non-Hodgkin's lymphoma also increased with increasing exposure (P less than .05), although the overall rate was similar to that of the general population (SIR = 1.06). The lung cancer rate was as expected (SIR = 0.97), but showed a weak association with CTPV exposure that was not statistically significant. No individual cause of death or incident cancer site was related to exposure to electromagnetic fields. Analysis of the joint effect of smoking and CTPV exposure on lung and bladder cancer showed the exposure response relationships to be independent of smoking.

Mortality among British Columbia pilots

We studied the mortality experience of all pilots who died in the province of British Columbia between 1950 and 1984, using proportional mortality ratios (PMR) and proportional cancer mortality ratios (PCMR). There were 341 deaths during that time in males whose usual occupation was listed as pilot. The PMR for aircraft accidents was significantly elevated (PMR = 3196, 95% C.I. 2810, 3634), and the PMR for atherosclerotic heart disease was significantly depressed (PMR = 47, 95% C.I. 30, 70). Although based on small numbers of deaths, and not statistically significant, elevated PCMRs were seen for cancers of the colon, brain, and nervous system, as well as for Hodgkin's disease. These findings suggest the need for further epidemiologic studies of commercial airline pilots.

A hierarchical coding system for occupational exposure

A 10-digit hierarchical method for coding occupationally encountered chemicals offering significant advantages over existing chemical coding systems has been developed and tested. With this unique system, substances are categorized and coded according to their composition and physical natures. Consequently, compounds of similar structure may be distinguished, and classes of similar compounds (for example, all halogenated organic compounds, all inorganic sulfates) can be readily retrieved. This novel coding system was developed to assist primarily in the identification of potential carcinogens in occupational studies using job exposure matrices. However, the system has wider applications as it can be employed by industry to facilitate data management and monitoring programs in the workplace.

Occupational associations among British Columbia male cancer patients

In a study of 6,389 male cancer patients diagnosed and treated at the Cancer Control Agency of British Columbia from 1950-1975, several associations were detected between occupation and specific cancers. Elevated risks for lung cancer were seen in miners, metal processors and machinists, while a reduced risk was seen in farmers. Lip cancer excesses were detected in individuals involved in several outdoor occupations, and melanoma excesses were seen for three groups of predominantly indoor workers. These results confirm previous findings in the literature, whereas the following associations have not been previously reported. Fishermen were found to have an excess of Hodgkin's Disease (RR = 3.0, 95% C.I. = 1.4,6.5), engineers are at an elevated risk of cancer of the pancreas (RR = 4.2, C.I. = 1.8,9.9), and forestry workers have an elevated risk of bladder cancer (RR = 1.7, C.I. = 1.1,2.6). Further studies will be needed to replicate the new associations detected here.

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.

Diet and histologic types of benign breast disease defined by subsequent risk of breast cancer

The authors investigated the relation between diet and histologic types of benign breast disease defined by subsequent risk of breast cancer in a case-control study of volunteers who entered the Vancouver Center of the Canadian National Breast Screening Study between 1983 and 1985. Proliferative benign breast disease (n = 124) was inversely associated with vitamin A supplementation (vitamin A user vs. nonuser, odds ratio (OR) = 0.5) and frequent green vegetable consumption (frequent vs. rare consumption, OR = 0.3), whereas severe atypias and borderline carcinoma in situ (n = 32) were directly associated with frequent meat fats consumption (frequent vs. rare consumption, OR = 3.2) with no association with vitamin A or vegetable consumption. No dietary relations were found for histologic types of benign breast disease at no increased risk for subsequent breast cancer (n = 274). The implications of these findings in relation to the etiology of breast cancer are 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.

Differences in incidence rates of cancers of the respiratory tract by anatomic subsite and histologic type: an etiologic implication

Data from nine population-based cancer registries participating in the Surveillance, Epidemiology, and End Results Program (1973-1982) were analyzed to determine whether the incidence of different histologic types of respiratory tract cancers varies by anatomic location. The variation in cancer incidence among respiratory tract subsites was remarkable for squamous cell carcinoma, but the variation was less prominent for adenocarcinoma. The rates of squamous cell carcinoma and adenocarcinoma along the airways correspond closely with the deposition pattern of large and small smoke particles, respectively. Also, the rates of adenocarcinoma parallel the distribution of surface glandular cells of the respiratory tract. Our results support the hypothesis that anatomy and physiology, in conjunction with size of particles in inhaled cigarette smoke, play an important role in the genesis of specific histologic types of respiratory tract cancers.

Retinoid chemoprevention timing and dose intensity

The concept of chemoprevention is generating increasing attention among oncologists. This article discusses the issue of dose of chemopreventive agents in relation to the stages of tumor development. Vitamin A-deficient animals have an increased susceptibility to cancer development, and epidemiologic studies have shown an inverse relationship between intake of food rich in vitamin A and/or beta-carotene and cancer risk. These data suggest that physiologic levels of these natural substances exert a protective effect against cancer development. In the presence of precursor lesions, however, this protective effect has been overwhelmed and pharmacologic doses of chemopreventive agents are required to induce regression or to arrest the progression of these lesions. Phase I pharmacologic and toxicologic studies, and Phase II dose-intensity investigation of chemopreventive agents in patients having precancerous lesions need to be carried out. Such studies would enable to select the least toxic effective chemopreventive dose for intervention trials in high-risk populations, which could then be undertaken based on evidence of activity.

Influence of estrogen receptor status on dietary risk factors for breast cancer

It has been suggested that the relation between diet and breast cancer may depend on estrogen receptor (ER) status. We examined the responses to a self-administered questionnaire on frequency of consumption of various foods by 493 women with breast cancer (160 with ER-negative tumours and 333 with ER-positive tumours) and 527 controls whose menopausal status was known. Analysis of the reported consumption of foods selected for their fat or carotene content showed no clear distinction in dietary factors between the ER-negative and ER-positive groups. Frequent consumption of meat fats generally increased the risk of both ER-negative and ER-positive tumours; there were no clear trends in risk associated with vegetable consumption for either ER group. Fish was the only item affecting the risk for ER-negative and ER-positive tumours differently, frequent consumption reducing the risk for the former (p = 0.02). The results do not support the hypothesis that ER status influences the relation between dietary fat consumption and risk of breast cancer.

Occupation and risk of cutaneous melanoma

Occupational mortality from cutaneous malignant melanoma was evaluated for deaths occurring in British Columbia from 1950-1978 by using age standardised proportional mortality ratios (PMR). For males, significantly elevated PMRs for melanoma were seen in managers and owners, accountants, architects, chemical engineers, and gardeners and nursery workers. Female school teachers were also at elevated risk of death from cutaneous melanoma.

Cancer mortality experience of woodworkers, loggers, fishermen, farmers, and miners in British Columbia

To evaluate occupational cancer mortality in British Columbia, we calculated the age-standardized proportional mortality ratios (PMR) and proportional cancer mortality ratios (PCMR) for 4,091 woodworkers, 5,457 loggers, 2,020 fishermen, 4,066 farmers, and 1,912 miners. Woodworkers 20-65 years old had significantly elevated risks of death from stomach cancer (PCMR = 128, P less than .01) and non-Hodgkin's lymphoma (PCMR = 140, P less than .05). Loggers appear to have an elevated risk of death from nasal sinus tumors (PCMR = 364, P less than .05). Fishermen had an elevated risk of stomach cancer (PCMR = 168, P less than .01). Farmers in British Columbia appeared to have excess risks of stomach (PCMR = 136, P less than .01) and liver cancer (PCMR = 173, P less than .05), but decreased risk from lung cancer (PCMR = 76, P less than .01). Miners had an elevated risk of death from lung cancer (PCMR = 127, P less than .05) and primary eye tumors (PCMR = 569, P less than .05).

Reproductive variables as possible confounders in occupational studies of breast and ovarian cancer in females

In a study of occupational mortality among all females dying at age 20 years or over in British Columbia during the period 1950 through 1978, significantly elevated proportional mortality ratios (PMRs) were seen for breast and/or ovarian cancer among teachers, nurses, office clerks, and sales clerks. Approximately 91% of the female deaths were recorded as occurring among "homemakers." When the PMRs were recalculated for "working women" only (ie., excluding homemakers), most of the excesses in risks for breast and ovarian cancer observed among the four occupational groups disappeared. The authors suggest that the differences in PMR values between all women and working women are due to protective higher parity and lower maternal age at first birth among homemakers as opposed to working women in general. In occupational studies of hormone-related tumors among women, every effort should be made to control for parity level and maternal age at first birth.

Occupational mortality patterns among British Columbia farm workers

To examine mortality risks for farm laborers proportional mortality ratios (PMRs) were calculated for 2,328 British Columbia farm workers who died at age 20 years or over during the period 1950 through 1978. Significantly fewer deaths than expected from degenerative heart disease (PMR = 91, p less than .01) and from all cancers combined (PMR = 78, p less than .001) were observed. Deaths from bronchitis and emphysema (PMR = 70, p less than .05) were also fewer than anticipated. Elevated risks of death were found for accidents (PMR = 129, p less than .001), for homicide (PMR = 242, p less than .01), and for pneumonia (PMR = 146, p less than .001).

Recent trends in incidence rates of pleural mesothelioma in British Columbia

A total of 64 cases of pleural mesothelioma were reported in British Columbia between 1973 and 1980, 54 in males and 10 in females. There was a significant (p less than 0.05) increase in the incidence among males. The overall incidence rates were 4.9 and 0.9 per million person-years for males and females respectively. The age distribution of the cases was roughly exponential up to age 70 years. Almost all of the cases were clustered in Cowichan Valley, Capital and Greater Vancouver counties, where there was a high level of shipbuilding activity 30 to 40 years ago. The increased incidence in males may be related to this activity, which involved exposure to asbestos.

Treatment of benign breast disease with vitamin A

Twelve patients with benign breast disease (BBD) were treated with 150,000 IU of vitamin A daily taken orally. All patients were symptomatic and had measurable or evaluable breast masses. At 3 months of treatment, complete or partial responses were observed in five patients, and marked pain reduction in nine was observed. Side effects were generally mild in nature, consisting mostly of skin and mucosal changes, and were rapidly reversible upon discontinuation of the drug. Treatment was interrupted or discontinued in only two patients, and the dosage of vitamin A was reduced in one on account of toxicity. No hepatotoxicity was observed. Investigation of the chemopreventive role of either vitamin A or retinoids in patients with BBD who are at high risk of developing breast cancer is suggested.

Cancer and aplastic anemia in British Columbia farmers

For evaluation of occupational mortality in agriculture, age-standardized proportional mortality ratios (PMR) were calculated for 28,032 male farmers with the use of British Columbia (B.C.) death registrations collected from 1950 to 1978. Farmers had significantly elevated risks of death from cancer of the lip (PMR = 191, P = .05), stomach (PMR = 119, P less than .0001), and prostate gland (PMR = 113, P less than .001). In addition, leukemia was higher than expected (PMR = 122, P less than .01), as was aplastic anemia (PMR = 174, P less than .01). The elevated risks were fairly consistent over the 29-year period for stomach, prostate gland, and lip cancer, as well as for leukemia. The PMR for aplastic anemia was highest for the years 1950-59 and declined over the next 19 years. Farmers also showed significant mortality deficits for several important cancer sites, including esophagus (PMR = 59, P less than .0001), colon (PMR = 84, P less than .001), larynx (PMR = 62, P less than .01), and lung (PMR = 66, P less than .0001) for the period 1950-78. More detailed studies in B.C. will be necessary to confirm and extend these cancer-agriculture associations.

Multiple myeloma, leukemia, and cancer of the ovary in cosmetologists and hairdressers

In order to evaluate occupational mortality, age standardized proportional mortality ratios (PMR) were calculated for 160 female cosmetologists and hairdressers and 1,001 male barbers and hairdressers utilizing cause of death and occupation statements from British Columbia death registrations collected from 1950 to 1978. Female cosmetologists had elevated risks of death from multiple myeloma (PMR = 619, p = .03) and ovarian cancer (PMR = 204, p = .09). Male barbers and hairdressers had no corresponding elevated risk of myeloma but had a significantly high risk of death from leukemia (PMR = 188, p = .05). Further detailed studies of these occupations would be worthwhile to confirm and extend these findings.

Pharmacokinetics of Lonidamine after oral administration in cancer patients

The pharmacokinetics of Lonidamine has been studied in cancer patients after single and chronic oral administrations. After single administration the plasma kinetics are highly variable, while the dose eliminated in the urine is over 70% in all subjects. This suggests an active but interindividually variable first-pass effect. After repeated administrations, both the residual plasma concentration before administration (C infinity min) and that obtained after drug intake (C infinity max) have been studied. The C infinity max values range from 4.5 to 25 micrograms/ml and C infinity min values from 0.4 to 7 micrograms/ml. In patients where a therapeutic response was noted, a mean value of 2.98 micrograms/ml for C infinity min was measured. In patients unresponsive to drug therapy the mean C infinity min was 1.5 micrograms/ml.

Phase I toxicologic study of Lonidamine in cancer patients

15 patients with metastatic cancer were treated with Lonidamine, a substituted indazole carboxylic acid active against the Lewis lung and Sarcoma 180 tumors. Single doses of 600 mg (350-400 mg/m2) mostly induced somnolence and gastro-intestinal side effects. Toxicity occurring during chronic administration of Lonidamine at doses ranging between 45 and 275 mg/m2 twice daily, mainly consisted of somnolence, myalgias, hyperesthesia and mild hair loss. Myalgias and hyperesthesias were markedly relieved with prednisone 5 mg twice daily. No laboratory abnormalities were seen. In 1 patient with breast cancer resistant to standard chemotherapeutic agents, a 30% reduction of measurable tumor masses was seen. In view of the lack of overlapping toxicity between Lonidamine and other chemotherapeutic drugs, and of its potential activity, it is suggested that phase II studies of Lonidamine be initiated at a dose of 135 mg/m2 twice daily.