Squamous cell carcinoma growth in irradiated tissue: a murine model for quantitative assessment of treatment

Locoregional recurrent and distant metastases from squamous cell carcinomas, despite multimodality therapy, remain troublesome clinical realities. Discrepancies in success rates of various surgery and radiation treatment regimens dealing with these problems are confusing to the clinician attempting to recommend the most beneficial treatments. There is a need for an experimental model to assess therapeutic effectiveness quantitatively from which guidelines for developing clinical trials may be suggested. In this study, we provide such a model. We injected DBA-2 mice with defined numbers of KLN-205 squamous carcinoma cells to obtain baseline growth characteristics; 216 animals had no previous irradiation. The remaining 131 received 30 Gy irradiation to the right leg 50 days before injection of the tumor cells. Tumor incidence, growth and number, and location of tumor metastasis were determined in both previously irradiated and nonirradiated groups. The data demonstrate a growth-retardant effect on tumor groups by the previous irradiation (tumor bed effect). The data also show that the incidence of hematogenously spread metastases was more frequent in mice in which tumors developed in previously irradiated tissue than in mice with tumors in nonirradiated tissue.