Clinical Symposia 3/1993 [antikvár]

Lung Cancer JAMES C. HARVEY, MD Attending Thoracic Surgeon Beth Israel Medical Center New York, New York Lung cancer is a disease of relatively modern times. Although the prevalence has increased over the last six decades, it was not until the 1950s that epidemiologic studies convincingly linked smoking-especially cigarette smoking- to the rising death rate attributed to lung cancer. In 1993, The American Cancer Society projects that about 170,000 new cases of lung cancer will be diagnosed, accounting for 18% of new cancers in men and 12% in women. The incidence of lung cancer has increased from 4 cases per 100,000 patient years in both men and women in 1930 to 74 cases in men and 27 cases in women in 1987. In men, the death rate recently seemed to reach a plateau, possibly because of a decrease in cigarette smoking that began in 1965 after the first Surgeon General's report linking smoking with lung cancer. However, the incidence continues to rise in women. These unhappy statistics can only be changed by prevention, early detection, and improved management. RISK FACTORS Case-control studies and pedigree analyses have identified somé families with increased rates of lung cancers; the familial component persists even after adjusting for smoking habits and environmental exposures. The fact that adenocarcinomas are more common in families with other cancers and inherited lung disorders suggests a genetic predisposition to this type of lung cancer. Behavioral scientists have demonstrated that somé people may have a genetic predisposition to continue smoking once the habit is acquired. Smoking By the turn of the century, cigarette smoking was replacing pipe smoking as the preferred mode of tobacco use. An increasing frequency of lung cancer observed during the 1930s and continuing into the 1990s is probably a result of this change in preference (Plate 1). As early as 1941, Ochsner and DeBakey called attention to the similarity between the rate of increase in cigarette sales in the United States and the rate of increase in lung cancer. In 1947, the Medical Research Council of Great Britain held a conference to determine if 2 EDWARD /. BEATTIE, MD Chief of Thoracic Surgery Beth Israel Medical Center New York, New York the dramatic increase in lung cancer deaths was real and to find a cause. A study was designed to investigate possible associations, including coal smoke and generál úrban atmospheric pollution, arsenicals (used in the treatment of syphilis), tobacco smoking, and other exposures thought to have increased during the previous 50 years. Neither of the investigators (Richárd Doll and A. Bradford Hill) suspected beforehand that cigarette smoking would be a major factor. General úrban atmospheric pollution was at the top of the list of probable causes. The initial skepticism regarding tobacco smoking may seem strange in retrospect because the association of pipe smoking with cancers of the lip and tongue was already known. However, these tumors were thought to be due to heat from the pipe stem. Doll and Hill's initial case-control study involved interviews with patients from 20 London hospitals who had suspected cancers of lung, stomach, and colon. The patients with lung cancer were matched for gender and age to a control group of patients who had diseases other than cancer. Many of the interviewed patients who were thought to have lung cancer, however, did not have it. In heavy smokers, the diagnosis of lung cancer was nearly always confirmed, whereas in nonsmokers, the diagnosis was frequently changed. The data for 650 men with lung cancer convinced Doll and Hill that there was a significant association between lung cancer and cigarette smoking. Other factors investigated in the study showed no significant association. Although the investigators believed that their study indicated a cause and effect relationship between smoking and lung cancer, they did not publish their findings until they could duplicate the results in other British cities. At the same time, Wynder and Graham published a paper suggesting that tobacco smoking was a possible etiologic factor in bronchogenic carcinoma. A few earlier small studies had alsó found an association between cigarette smoking and lung cancer, but the studies by Wynder and Graham and by Doll and Hill were larger and had especially high standards for case-control methodology. The studies evaluated a broad rangé of CLINICAL SYMPOSIA