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2755177 
Journal Article 
Incidence and Nature of Tumors Induced in Sprague-Dawley Rats by gamma-Irradiation 
Gross, L; Dreyfuss, Y; Faraggiana, T 
1988 
Yes 
Cancer Research
ISSN: 0008-5472
EISSN: 1538-7445 
NIOSH/00180327 
48 
9 
2451-2453 
Induction of tumors by gamma irradiation was studied in rats. Young adult Sprague-Dawley-rats were irradiated whole body with 150 rad gamma rays two to four times at weekly intervals. Rats were maintained until death. Tumor development was recorded, and tumors were examined histologically. Eighteen of 19 females irradiated twice developed tumors at an average age of 11.4 months. Seventeen were in the mammary gland area. Two were adenocarcinomas and one was a sarcoma. The other 15 were benign (14 fibroadenomas and one leiomyofibroma). Seven of 14 males irradiated twice developed tumors at an average age of 10.4 months. Three tumors were subcutaneous sarcomas and three carcinomas. One rat developed two benign fibroadenomas. In rats receiving three doses of radiation, 20 of 23 females and five of 13 males developed tumors at average ages of 9.1 and 7.5 months, respectively. Six of the tumors in the females were malignant, the rest benign. Four of the tumors that developed in the males were malignant. In rats receiving four doses of radiation, 17 of 19 females developed mammary tumors at an average age of 9.4 months. Four were malignant, the rest were benign fibroadenomas. Four of 12 males developed tumors at an average age of 10.5 months. Two were malignant. The histological characteristics of the tumors developing in the irradiated animals were similar to those developing spontaneously in the controls but the incidence of tumors was higher in the irradiated animals. The authors conclude that two consecutive whole body gamma irradiations of 150 rad are sufficient to induce tumors having latency periods of 3 to 18 months. Untreated rats of the same strain also develop similar tumors except that they are usually nonmalignant. The etiology of tumors developing spontaneously or as a result of radiation in rats is unknown.