Etiological Factors

Cigarette:

The most common etiologic factor by far is the inhalation of cigarette smoke. While there has been an increase in all types of lung cancer since the introduction of cigarettes into the marketplace, there is much evidence to indicate that the incidence of small cell carcinoma is related to heavy smoking (greater than 1 1/2 packs per day).

Ionizing Radiation:

The role of ionizing radiation has been extensively studied in uranium miners and patients. Patients exposed to this have shown an increased incidence of lung cancer. Small cell carcinoma accounts for 70% of excess cases. Cigarette smoking is an additive risk factor in this group with men who were both heavy smokers and exposed to heavy radiation. They were report having 67 times more lung cancer than those who were not exposed to either.

Chlormethyl Ethers:

Chlormethyl ethers are the only chemical agents of the many postulated that have shown a definite link t the increased incidence of small cell carcinoma (5.4 times that is expected in several studies). No other chemicals have shown a clear association with small cell carcinoma.