Clinical Study of Multiple Primary Cancer Involving the Lung

The incidence rate of multiple primary cancer involving the lung was 11.3% of all primary lung cancer resected at the Cancer Institute Hospital till 1984. Colorectal cancer was most frequently associated with lung cancer. As to the histological type of lung cancer, incidence of squamous cell carcinoma was more than that in single lung cancer. In 60 cases of multiple primary cancer, almost half of the cases were metachronous double cancers, one of which was subsequent lung cancer. In cases of metachronous double cancer, compared to cases of prior lung cancer, cases of subsequent lung cancer showed the following differences. (1) The interval between the first and second cancer is longer. (2) Histologically, adenocarcinoma is more frequent. (3) The stage of lung cancer is more advanced. (4) The cause of death is lung cancer in most cases. (5) Prognosis is poor. It is suggested that even cases of multiple primary cancer may obtain better prognosis by intensive follow up and resultant earlier diagnosis of the second cancer.