VITAMIN-A AND CANCER PREVENTION I - OBSERVATIONS IN WORKERS PREVIOUSLY EXPOSED TO ASBESTOS AT WITTENOOM, WESTERN-AUSTRALIA

Our aim was to describe a vitamin A-based cancer prevention program fo r 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 lune 1990 a nd 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 (ei ther 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 co mpared, Mortality in both groups was higher than expected (standardise d mortality ratio 1.23 in program subjects and 1.67 in comparison subj ects). After adjustment for age, smoking and asbestos exposure, the re lative rates in participants compared with non-participants was below 1 for all examined cancers and causes of death, For mesothelioma and l ung cancer, group differences increased with time from entry, whereas other differences dissipated with time. No significant side effects we re reported, In conclusion, program participants had significantly low er mortality than non-participants, but the rates of the 2 groups conv erged with time. (C) 1998 Wiley-Liss, Inc.