2ND PRIMARY-CANCER FOLLOWING LARYNGEAL-CANCER WITH SPECIAL REFERENCE TO SMOKING-HABITS

The risk of developing a second primary cancer following laryngeal cancer was estimated by following-up 472 male laryngeal cancer patients for an average of 8.6 years by means of record linkage to the Osaka Cancer Registry. Of these patients, 115 developed a second cancer other than laryngeal cancer, whereas the expected number derived from the incidence rates among Osaka residents was 51.4 (relative risk (RR) = 2.2, 95% confidence interval = 1.85-2.69). Cumulative risk of developing a second primary cancer was estimated to be 31.1% at 15 years after laryngeal cancer. By site, the risks were significantly increased for tobacco-related cancers, RR = 24.5, 6.1 and 2.3 for cancers of the oral cavity & pharynx, esophagus and lung, respectively. Also, the risks were higher among heavy smokers for cancer of the oral cavity & pharynx and esophagus than among light smokers. No adverse effects of radiotherapy for laryngeal cancer on the development of thyroid cancer, lymphoma and leukemia were observed. The present study suggests the necessity of following-up laryngeal cancer patients over a long period in order to enable the early detection of tobacco-related cancer.