[Epidemiology of multiple primary cancer].

A definition of MPC by IARC and SEER and new methods for determining independent clonality of each MPC were introduced. A trend in frequency of multiple primary cancer (MPC) has been increasing in the National Cancer Center Hospital during 1962-1989. Frequent sites to cause MPC were esophagus (8.4%), larynx (8.2%), bladder (7.9%), colon (7.0%), oro-pharynx (5.5%), and an overall incidence was 2,082/54,888 (3.8%). The association of MPC showed a downstream relationship along the alimentary canal. A common exposure to carcinogenic stimuli in the digestive system was suggested. Smoking tobacco was a risk of frequent oro-pharynx, larynx and lung MPC by a case-control study. Effects of chemotherapy, irradiation and other treatments to cause MPC were introduced. A risk of hormone treatment and immunosuppressive drugs after tissue transplantation was discussed.