Second primary cancer after treatment of invasive carcinoma of the uterine cervix, compared with those arising after treatment for in situ carcinomas. An effect of irradiation? A cancer registry study.

A cancer registry cohort of 16,704 cases of invasive carcinoma of the uterine cervix and 56,116 cases of in situ carcinomas of the uterine cervix was followed up and second new primary cancers were recorded. The invasive carcinomas contributed 127,118 woman-years at risk and the in situ carcinomas contributed 453,362 woman-years at risk. The main treatment for the invasive carcinomas had been radiotherapy and for the in situ carcinomas, conization and other types of surgical intervention. 767 new primaries occurred after treatment of invasive carcinoma of the uterine cervix, compared with 644.5 expected. O/E is 1.19. After the in situ carcinomas, 1,421 malignant tumors were observed, vs. 1,188.0 expected (O/E 1.19). If, however, cases of invasive carcinoma of the uterine cervix after in situ carcinomas are excluded, the ratio observed/expected is 1.10. For some sites the increased observed/expected ratios were found after both invasive and in situ carcinomas, which speaks for some common carcinogenic effect other than irradiation (for instance, in bronchus and trachea, pharynx, nose, sinus and larynx, but also in rectum, urinary bladder, other female genital organs, pancreas, lymphosarcoma, as well as acute and non-lymphatic leukemia). A lower risk than expected--after both in situ and invasive carcinoma of the uterine cervix--is observed for breast cancer, cancer of the corpus uteri and for multiple myeloma. However, analyses based on time since treatment provide evidence of a carcinogenic effect of irradiation, especially in intensively irradiated organs such as bladder, rectum, corpus uteri and ovary, and also for acute and non-lymphatic leukemia.