Occurrence of second primary cancers among patients with cervical cancer in Osaka, Japan.

Using the data accumulated in the Osaka Cancer Registry, we conducted a study on the effect of radiotherapy for cervical cancer in causing second primary cancers. Two groups of patients with cervical cancer, 1,767 who were given radiotherapy and 1,377 who were not, were followed for 7-9 years on average. In the radiotherapy group, 79 women had second primaries, and in the nonradiotherapy group, 23 did. These figures were compared with the expected cancer incidence for all sites. In the radiotherapy group, a significantly high observed-to-expected ratio was noted in cancers of the rectum, lung, and bladder. The nonradiotherapy group showed no site with a significantly high observed-to-expected ratio. Factors causing the increased level of lung cancer were studied. Some evidence indicated the excess was probably not related to smoking but to radiation, although the mechanism is unknown.