1 The death rate due to cancer of the lungs has increased more than800 percent in males and has more than doubled in females during the last 25years. It is considerably higher in urban and industrial areas than in ruraldistricts. There are many possible causes, but it is still controversial whichare most blameworthy. Those factors which have been mentioned most frequentlyare the presence of foreign particles and other irritants in the air (smokeparticles, smog, exhaust fumes), and the smoking of cigarettes and cigars.
2 Numerous studies have demonstrated a striking correlation betweenthe death rate from lung cancer and smoking habits. Among heavy smokers — 21 to 30 cigarettes per day — the mortality rate from lungcancer is nearly 17 times the rate from nonsmokers. It is expected the deathrate among women will increase as the present high rate of smoking among womenhas its effect.
3 Sometimes cases of lung cancer are discovered at the time an x-rayis taken for the purpose of detecting tuberculosis. Too often, however, acurrent emphasis upon the danger of exposure to radiation1 fromX-ray machines can frighten people away from routine chest X-rays and thusprevent an early diagnosis of lung cancer. Early detection is absolutelyessential if any possibility of cure is to be maintained2. ModernX-ray machines in competent hands pose such slight danger, at least to thoseover 40 years of age, that this would be much more than offset by theadvantages of discovering a tumor while it is small enough to be completelyremoved.3
4 A common form of lung cancer is bronchogenic carcinoma4，so-called because the malignancyoriginates in5 a bronchus. The tumor may grow until the bronchus isblocked, cutting off6 the supply of air to that lung. The lung thencollapses, and the secretions trapped in the lung spaces become infected, witha resulting pneumonia or the formation of a lung abscess. Such a lung cancercan also spread to cause secondary growths in the lymph nodes7 ofthe chest and neck as well as in the brain and other parts of the body. Theonly treatment that offers a possibility of cure, before secondary growths havehad time to form, is to remove the lung completely. This operation is calledpneumonectomy.
5 Malignant tumors of the stomach, the breast, the prostate gland8and other organs may spread to the lungs, causing secondary growths.
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