One hundred forty-four heavy-smoker (125 males, 19 females) volunteers with at least 15 packet-year of smoking experience (number of daily packets of cigarettes X number of years of smoking) underwent bronchoscopy with systematic biopsies in ten sites of the bronchial tree. No morbidity was related to the fibroscopy procedure. Each biopsy was cut into ten sections and an index of metaplasia (IM) was calculated: IM = number of sections with epidermoid metaplasia/number of sections examined X 100. A highly significant statistical correlation was observed (P = 10(-4)) between the IM and the amount of cigarettes smoked (slope of the curve: 0.23). Sex appeared to play an important role in the incidence of metaplasia, since 84% of the examined females had an IM less than 15% versus 48% of the males (P adjusted for individual tobacco consumption in packet-years less than 0.01). Early study of HLA phenotype (locus A) failed to detect a link between HLA and risk of tobacco-induced epidermoid metaplasia.

Vitamin A and its derivatives, so-called retinoids, can prevent squamous metaplasia induced not only by vitamin A deficiency but also by carcinogenic hydrocarbons. An aromatic retinoid, such as ET1, has been shown to prevent chemically induced papillomas in mice and to amplify certain immunologic reactions. Heavy smokers, 106 volunteers, were submitted to fibrobronchoscopy with bronchial biopsies. An index of metaplasia (IM) was calculated on the basis of microscopical examination of a total of 9,633 sections of 1,010 biopsies. Despite the subjectivity of the estimates of cigarette consumption, this was significantly (P less than 0.02) and positively correlated to the IM. Eighty-five percent of the women had a low IM as compared to only 42% of the men (P less than 0.01), although there was no significant difference in the reported cigarette consumption. Fifty-two subjects had an IM greater than 15% and were given 25 mg ET1 orally daily for 6 months. The bronchoscopy was repeated in 30 patients following completion of the 6-month treatment. The IM was significantly (P less than 0.01) reduced after treatment.

70 volunteers who had had at least 15 packetyears of smoking experience underwent bronchoscopy and bronchial biopsy. The degree of metaplasia (IM, index of metaplasia) was calculated for each of them. The 34 who had an IM of >15% were given a 6-month course of a retinoid, etretinate. 12 have completed the course, and their IM scores have dropped significantly.