Development of Malignant Tumors following Irradiation for Preexisting Tumors:Study Based on Autopsy Cases of Double Cancer

Carcinogenesis is a significant matter among the late pathologic effects of therapeutic irradiation which is now used for malignant tumor. Accumulation and analysis of cancer cases following radiation therapy for malignant tumor seem necessary to search for ways to follow up such patients. For the purpose of screening secondary cancer cases following irradiation for a primary malignant tumor, we first selected 259 cases of double cancer from about 13,000 autopsied cases of Nagasaki University and its related hospitals, and reviewed probable cases of secondary carcinogenesis based on their clinical and autopsy records. The criteria used for selection of most probable cases were that 1) radiation therapy was performed for the first cancer, 2) the second cancer developed at the site of irradiation field, and 3) the interval from radiation therapy to detection or onset of the second cancer (latent period) was five years or more. We found 6 cases of most probable radiation induced cancer, all females. The first cancer was cervical cancer in 4 cases, thyroid cancer in 1 case and lymphosarcoma in 1 case. The radiation induced cancer was carcinoma in 4 cases, and sarcoma in 2 cases. The latent period ranged from 5 to 23 years, the mean being 13.3 years. The clinical and pathological features of these cases with special reference to radiation-carcinogenesis relationship are reported. Two A-bomb survivors were included among these 6 cases