Vitamin A and cancer prevention II: Comparison of the effects of retinol and β-carotene

Abstract

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 β‐carotene or retinol. Subjects were assigned randomly to take 30 mg/day β‐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 β‐carotene. The relative rate of mesothelioma (the most common single cause of death in our study) for those on retinol compared with those on β‐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 β‐carotene. The finding of significantly lower rates of mesothelioma among subjects assigned to retinol requires further investigation. Int. J. Cancer 75:362–367, 1998. © 1998 Wiley‐Liss, Inc.

Gynecologic and Breast Cancers in Women After Exposure to Blue Asbestos at Wittenoom

“…For the residents' cohort, the following public records were searched (with the percentage of people they identified in parentheses): state primary school records (22%), general practitioner and Wittenoom hospital records (20%), the state Electoral Roll for the Pilbara region (12%), questionnaires sent to former Australian Blue Asbestos workers (14%), and participants in a cancer prevention program (18%; refs. 24,25). Table 1 shows in detail the establishment of the residents' cohort.…”

“…All former residents traced to an address in Australia (n = 3,244, 64%) were sent a questionnaire in 1993, except 641 (13%), who were participating in the cancer prevention program and on whom the information was already available (24,25). The questionnaire ascertained their asbestos exposure experience including place and dates of residence at Wittenoom, whether they lived with and/or washed the clothes of an Australian Blue Asbestos worker, as well as demographic characteristics.…”

Agreement between a brief food frequency questionnaire and diet records using two statistical methods

“…A reliability study was conducted within a randomized clinical trial (the Vitamin A Program) which was designed to examine the efficacy of beta carotene and retinol (preformed vitamin A) supplements in reducing the risk of lung cancer, mesothelioma and possibly other malignancies after asbestos exposure 11 . Participants for the Vitamin A Program n 2769 were recruited from two large cohorts of former workers and residents of an asbestos mining and milling town in Western Australia 12 .…”

Serum Levels of Alpha-Tocopherol, Vitamin C, Beta-Carotene, and Retinol in Malignant Pleural Mesothelioma

“…In Australian study where 1,024 asbestos workers were enrolled in, the subjects were randomized to either β-carotene or retinol groups (De Klerk et al, 1998). After the follow-up period, no difference in lung cancer incidence was found, but the authors found that daily retinol was associated with lower rate of mesothelioma in crocidolite-exposed individuals, compared with daily β-carotene, which seemed to have no significant effect.…”