Experimental studies on metastases from an irradiated tumor

This study was carried out to determine the effect of irradiation of a tumor on the development of lung metastases. SANH, a spontaneous sarcoma, was isotransplanted in the right thighs of C3H mice which were either locally preirradiated (30 Gy: TBR) or non-irradiated. When the tumors had grown to 7 mm in diameter, they received 20-30 Gy of electron beams (RTx). The tumor-bearing legs were amputated at various tumor sizes, and the incidence of metastasis and number of lung nodules were compared in each treatment group. The incidences of metastases from 7 mm tumors in mice with regrowing tumors after RTx (30 Gy) and non-irradiated mice were 28% and 4%, respectively. When tumors grown in preirradiated legs were removed at 7 mm in diameter, the incidence of metastases (58%) was also enhanced by preirradiation of the tumor bed. Seven millimeter tumors that were growing in TBR legs and received RTx (20 Gy) developed a higher incidence (82%) and greater numbers of metastases than either the RTx or TBR groups. To determine the relationship between the interval of tumor bearing and development of metastases, tumors were removed at various intervals after tumor transplantation in 4 groups, namely, non-irradiated, TBR, RTx and TBR with 20 GyRTx. Lung metastases came later but increased steeply in mice given either TBR or RTx, compared with non-irradiated mice. Tumors growing in TBR and receiving RTx (20 Gy) developed many more metastases than any other group.(ABSTRACT TRUNCATED AT 250 WORDS)