THE VARIATION OF CELL-TYPE DISTRIBUTION IN LUNG-CANCER - A STUDY OF 10,910 CASES AT A MEDICAL-CENTER IN TAIWAN BETWEEN 1970 AND 1993

The rise in the incidence of lung cancer has been associated with shif ts in histologic distribution. A study was conducted to investigate ch anges in the cell type distribution in lung cancer in relation to age, sex, and smoking history, based on a retrospective analysis of 10,910 proven cases of lung cancer at the Veterans General Hospital-Taipei d uring the period from 1970 to 1993. The diagnosis in each case was sub stantiated by histologic samples from the original tumor site in the l ung. Detailed smoking histories were obtained by personal interview at the time of the first admission. Adenocarcinoma (38.3%) was the most common type of lung cancer, followed by squamous cell carcinoma (37.1% ) and small cell carcinoma (12.2%). Over the study period, the inciden ce of squamous cell carcinoma decreased from 46.4% to 36.2% in men (P< 0.005), adenocarcinoma increased from 30% to 36% in men (P=0.001) and 50.7% to 64.8% in women (P=0.008), and small cell carcinoma increased from 7% to 14% in men but showed no significant change in women. Adeno carcinoma exhibited a marked increase in both men and women, and surpa ssed squamous cell carcinoma as the most frequent type of lung cancer. Lung cancer among younger men, and among non-smoking older men and wo men, was more often adenocarcinoma. Small cell carcinoma showed a sign ificant increase among males, differing from the trend for squamous ce ll carcinoma in men, though both are strongly associated with smoking. These findings suggest factors other then cigarette smoking could inf luence the development and distribution of lung cancer.