asbestos--crocidolite and Myocardial-Ischemia

Our aim was to describe a vitamin A-based cancer prevention program for former asbestos workers and to check for possible harmful effects by comparing rates of disease and death in study subjects with subjects who chose not to join. All subjects had been occupationally exposed to crocidolite at Wittenoom Gorge between 1943 and 1966; 1,677 subjects indicated interest in the program and 1,203 joined between June 1990 and May 1995. Comparison subjects consisted of 996 former workers known to be alive in Western Australia in 1990 who did not join the program. Program subjects were provided with annual supplies of vitamin A (either synthetic beta-carotene or retinol), help in quitting smoking and dietary advice. The comparison group received only mail contact. Both groups were followed up to December 1994 for vital status and cancer information, and rates of cancer and death from various causes were compared. Mortality in both groups was higher than expected (standardised mortality ratio 1.23 in program subjects and 1.67 in comparison subjects). After adjustment for age, smoking and asbestos exposure, the relative rates in participants compared with non-participants was below I for all examined cancers and causes of death. For mesothelioma and lung cancer, group differences increased with time from entry, whereas other differences dissipated with time. No significant side effects were reported. In conclusion, program participants had significantly lower mortality than non-participants, but the rates of the 2 groups converged with time.

Topics: Adult; Aged; Aged, 80 and over; Anticarcinogenic Agents; Asbestos, Crocidolite; Female; Humans; Lung Neoplasms; Male; Mesothelioma; Middle Aged; Myocardial Ischemia; Occupational Exposure; Vitamin A

Former blue asbestos workers known to be at high risk of asbestos-related diseases, particularly malignant mesothelioma and lung cancer, were enrolled in a chemo-prevention program using vitamin A. Our aims were to compare rates of disease and death in subjects randomly assigned to beta-carotene or retinol. Subjects were assigned randomly to take 30 mg/day beta-carotene (512 subjects) or 25,000 IU/day retinol (512 subjects) and followed up through death and cancer registries from the start of the study in June 1990 till May 1995. Comparison between groups was by Cox regression in both intention-to-treat analyses and efficacy analyses based on treatment actually taken. Median follow-up time was 232 weeks. Four cases of lung cancer and 3 cases of mesothelioma were observed in subjects randomised to retinol and 6 cases of lung cancer and 12 cases of mesothelioma in subjects randomised to beta-carotene. The relative rate of mesothelioma (the most common single cause of death in our study) for those on retinol compared with those on beta-carotene was 0.24 (95% CI 0.07-0.86). In the retinol group, there was also a significantly lower rate for death from all causes but a higher rate of ischaemic heart disease mortality. Similar results were found with efficacy analyses. Our results confirm other findings of a lack of any benefit from administration of large doses of synthetic beta-carotene. The finding of significantly lower rates of mesothelioma among subjects assigned to retinol requires further investigation.

Topics: Adult; Aged; Aged, 80 and over; Anticarcinogenic Agents; Asbestos, Crocidolite; beta Carotene; Female; Humans; Incidence; Lung Neoplasms; Male; Mesothelioma; Middle Aged; Myocardial Ischemia; Occupational Exposure; Patient Compliance; Risk Factors; Smoking; Vitamin A