Identification of Cases for Analysis

This study was undertaken to determine the relation between radiographic and histological manifestations of pulmonary asbestosis (interstitial fibrosis) in insulation workers who had died of lung cancer. Of 450 confirmed deaths from lung cancer a chest radiograph suitable for determining evidence of pneumoconiosis was obtained in 219. Of these cases, 138 also had a tissue specimen submitted that was suitable for histological study to determine the extent of histological fibrosis. There was a significant albeit limited correlation between the radiographic and histological findings (r = 0 27, p < 0-0013). All 138 cases had histological evidence of parenchymal fibrosis; in 25 (18%), however, there was no radiographic evidence of parenchymal fibrosis. In 10 cases (7%) both parenchymal and pleural disease were undetectable on the radiograph. Thus a negative chest radiograph does not exclude the presence of interstitial fibrosis (asbestosis) in a substantial proportion of insulation workers previously exposed to asbestos who develop lung cancer. Cancer of the lung is a leading cause of death in workers exposed to asbestos.' 5 For example, it has been found to account for as much as one fifth (21 %) of deaths in a large prospective mortality study of asbestos insulation workers.6 In individuals with lung cancer there are many different ways to assess retrospectively whether or not they have had significant exposure to asbestos. In the clinical setting exposure is often inferred from the presence of non-malignant effects of asbestos exposure: pleural fibrosis and interstitial pulmonary fibrosis. Histopathologically, asbestosis includes diffuse interstitial pulmonary fibrosis developing as a consequence of inhaling asbestos fibres; it is usually associated with the presence of asbestos bodies, although these may vary in number and ease of demonstration.7 Clinical studies in man, however, often do not use histopathological criteria for the diagnosis of asbestosis but the more easily obtained and less invasive chest x ray (and clinical) data. Such radio*Present address: Department of Environmental and Community Medicine, UMDNJ-Rutgers Medical School, Piscataway, NJ 08854. Accepted 14 April 1986 logical and clinical evidence has been reported to be less sensitive to the presence of asbestosis (and other types of interstitial fibrosis) than histopathological examination.8 9 This study examines further the relation between the radiographic and histopathological evidence of asbestosis in a population of asbestos insulation workers with lung cancer. As part of a continuing cohort mortality study of 17 800 members of the insulation workers' union (International Association of Heat and Frost Insulators and Asbestos Workers, AFL-CIO, CLC), we examined deaths from lung cancer which occurred between January 1967 and September 1983.