Vitamin A and cancer prevention I: Observations in workers previously exposed to asbestos at Wittenoom, Western Australia

Abstract

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 β‐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 1 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. Int. J. Cancer 75:355–361, 1998. © 1998 Wiley‐Liss, Inc.

Cancer incidence among women and girls environmentally and occupationally exposed to blue asbestos at Wittenoom, Western Australia

“…We have used various means to reduce our loss to follow up; tracing on the electoral roll (voting is compulsory in Australia and the electoral roll is carefully maintained), searches of the electronic white pages and participation in a cancer prevention program. 16 Italian migrants to Wittenoom who subsequently returned to Italy have been traced in Italy, but this information relates to male ABA workers and not their wives or families. 29 Twenty two percent of the women were defined as lost to follow up most from the time they left Wittenoom.…”

“…All women from both cohorts without a death record and who were not attending a cancer prevention program, 16 were searched for in the Marriage Register of WA to determine if a change of surname had occurred. The search commenced from the year they were last known to be alive.…”

Fruit, vegetable, vitamin A intakes, and prostate cancer risk

“…14,15 In July 1990 all surviving members of the Wittenoom workers cohort who could be traced (n ¼ 2373) were invited to take part in a cancer prevention programme to examine the efficacy of b-carotene (synthetic all-trans) and retinol (retinyl palmitate) supplements (hereafter referred to as vitamin A supplements) in reducing the risk of malignant mesothelioma, lung cancer and other cancers. 16 The programme was subsequently opened to members of the Wittenoom residents cohort and persons who had experienced an equivalent of at least 3 months of full time occupational exposure to crocidolite elsewhere (that is, not at Wittenoom), for example, carpenters, waterside workers, plumbers. These two groups were not actively recruited.…”

Serum levels of folate, lycopene, β-carotene, retinol and vitamin E and prostate cancer risk

“…This was a chemoprevention programme commenced in 1990, which examined the efficacy of vitamin supplements in reducing the risk of malignant mesothelioma, lung cancer and other cancers (Musk et al, 1998). We conducted a prospective nested case -control study of serum folate, lycopene, b-carotene, vitamin A and vitamin E concentrations and prostate cancer risk among those suffering with subsequent incident prostate cancer and randomly selected age-matched controls.…”