[Epidemiological studies on multiple primary cancers--observations on the second primary cancers among cervical cancer and laryngeal cancer cases]

Two epidemiological studies on multiple primary cancers were conducted. The first one was 7-9 years' follow up among cervical cancer cases (1,767 radiotherapy and 1,377 non-radiotherapy cases) registered in the Osaka Cancer Registry. The number of observed second primaries was significantly higher than the expected numbers at the rectum, bladder, lung and all sites in the radiotherapy group only. The other was a 7 years' follow up study on 532 laryngeal cancer cases. Higher incidence than expected second primaries were observed at the mouth and pharynx, esophagus and lung and all sites. The factors associated with these results were analyzed in relation to radiotherapy and smoking. Through these studies, the authors proved the usefulness of the data accumulated in a population-based cancer registry, especially in finding the multiple primaries, surveying prognosis of subjects and controls, and calculating expected numbers using the incidence data from the general population.