Lung Cancer

Pulmonary tumors may be primary or secondary and benign or
malignant. Their cause is unknown, but a statistical
relationship exists between cigarette-smoking and lung
cancer. Primary carcinoma of the lung is responsible for 5
to 10% of all deaths from cancer and the disease is
steadily increasing in frequency. It is more common in men
though the incidence is increasing in women. Most cases
occur between ages 40 to 70. 

The clinical presentation depends on the nature of the
tumor and its location. The patient may be asymptomatic if
the tumor is in a "silent" area; 90% of patents with
primary carcinoma of the bronchus complain of a cough and
in 50% it is the first symptom. In patients who already
have a chronic cough, an alteration in its character or
severity may cause suspicion. A localized wheeze indicates
partial obstruction of a bronchus. Obstruction of a large
broncus causes shrinkage of chest wall and diminution of
chest movement and breath sounds. Sputum is often scanty
and mucoid unless an infection (pneumonitis or lung
abscess) occurs . Sever, constant, nonpleuritic pain is a
peculiar and not infrequent manifestation. 

Not infrequently, an inapparent bronchogenic carcinoma may
first manifest itself in a remote metastasis, especially in
the brain. In advanced disease, the patient may present
with nonspecific symptoms such as weight loss, anorexia,
and weakness. Intrathoracic extension of the tumor may
produce pleuritis, often with pleural effusion: hoarseness
due to involvement of the recurrent laryngeal nerve. 

Diagnosis involves not only detection and classification of
the tumor but also determination of the extent of its
spread and its operability. Often the chest x-ray is the
only abnormality in an asymptomatic patient and thus it
provides the greatest likelihood of early diagnosis. In
addition to the tumor, the chest x-ray may show signs of
bronchial obstruction such as overinflation or infection,
elevation of the diaphragm. 

About 60 to 70% of cases of bronchogenic carcinoma can be
diagnosed from sputum cytology. The diagnosis is usually
established by bronchoscopy, either by direct visualization
and biopsy of the tumor or by examination of bronchial
washings. A thoracotomy and biopsy may be necessary to
establish the diagnosis in some cases. 

The average survival time of patents with untreated
carcinoma of the bronchus is 9 months. The overall 5-yr
survival rate is less than 10%.
 
Cigarette smoke contains more than 4,000 different
chemicals, many of which are carcinogens (may cause
cancer). The three of the most damaging toxins are
nicotine, tars, and carbon monoxide. Second-hand smoke
inhaled by both smokers and nonsmokers is another important
cause of lung cancer. Smoking is responsible for 90% of
lung cancer deaths among men, 79% among women. Also smoking
accounts for about 30% of all cancer deaths. Smokers that
inhale two or more packs of cigarettes a day, have a cancer
mortality rate 12-25 times greater than a nonsmokers. The
risk of lung cancer falls dramatically within a couple
years if smoking is stopped. 

Radon is the second leading cause of lung cancer. It is a
radioactive gas found in the earth's rocks and soil, formed
by the natural breakdown of radium. Excessive exposure of
radon in the home may increase the risk of lung cancer
especially in smokers. If the radon levels are found to be
to high, remedial actions should be taken.
 
Another cause of cancer is on the job exposure to
carcinogens. The best known carcinogen is asbestos. Others
include nickel, chromate, and vinyl chloride.