Lung cancer in individuals less than 50 years of age.

The aim of this study was to compare the epidemiologic, clinical, and laboratory characteristics and survival rates of younger and older patients with lung cancer. We studied 1340 patients who were histopathologically diagnosed as having lung cancer from 1990 to 2005. Based on prior reports, we defined "younger" as individuals less than 50 years old. The patients were classified into two groups: <50 years (the younger group) and >/=50 years (the older group). Of the 1340 patients, 179 (13.4%) were in the younger group and 1161 were in the older group. In the younger group, exposure to occupational risk factors was a risk factor for lung cancer, while in the older group, smoking was a risk factor. At the time of diagnosis, chest pain was more common in the younger group, while in the older group, cough, dyspnea, and hilar enlargement on chest X-ray were more frequent. The incidence of adenocarcinoma and small-cell carcinoma was greater in the younger group, while squamous cell carcinoma was more common in the older group. Metastasis rates were significantly different between the two age groups: 52.0% of the younger group presented with stage IV disease compared with 43.5% of the older group. Although fewer younger than older patients were not able to receive or rejected anticancer therapy, the overall survival was similar in both groups. These data indicate that lung cancer had different etiopathogenetic characteristics in younger patients, which may have clinical implications. By planning preventive measures based on these characteristics, more efficient use of resources can be achieved.