Arrest and retention of circulating cancer cells in the lungs of animals with defined metastatic status.

The arrest and retention patterns in lung tissues of [125I]-5-iododeoxyuridine-labeled Lewis lung carcinoma cells injected into the systemic circulation of tumor-bearing (TB) mice with defined metastatic status and non-tumor-bearing mice were determined. The presence of overt lung metastases did not significantly alter the arrest or subsequent rates of release of cancer cells compared with non-tumor-bearing controls. However, the percentage of cancer cells retained in the 3-week TB animals was significantly greater than that in the 1-week TB mice. In 3-week TB animals, 4 times as many cancer cells were arrested in the "noninvolved" lung tissues than in the metastases. The relative vascularities of the metastases and lung tissues were assessed following injection of 51Cr-labeled erythrocytes, and from these and published data it is suggested that major factors determining the differential distribution of cancer cells are the relative areas of microvascular endothelium and blood flow per g in the lungs and metastases.