Comparison of Natural and Artificial Lung Metastases from a Murine Tumour of Spontaneous Origin

The metastatic potential of the non-immunogenic CBA SA F tumour was investigated. Eradication of subcutaneous tumours of different sizes with 80Gy of X-rays resulted in lung metastases incidence increasing from 0 to 100% as the primary tumour size increased from 2 to 10mm. The number of metastases also increased and the average survival time decreased with increasing primary tumour size at treatment. The survival times suggested slower growth in lungs compared with subcutaneous sites. A bioassay for circulating tumour cells indicated there were less than 30 cells per ml venous blood in mice with tumours less than 12mm in diameter.