To the Editor.—
The essay by Krishnamurthy et al (237:2504-2506, 1977) demonstrates the importance of total body imaging for detection of metastatic bone disease. The authors' findings also verify variations in routes of metastasis that depend on sites of the primary tumors.For example, primary neoplasms of the breast and prostate metastasized preponderantly to axial bones because these tumors frequently pass via the vertebral venous system (235:2524, 1976). In contrast, metastases from lung cancer involved appendicular and axial bones with about equal frequency because lung tumors gain access to the general arterial circulation by invading the pulmonary veins. (Malignant neoplasms rarely penetrate arterial walls.) Distribution of metastases by way of the arterial circulation would not be expected to favor one set of bones over the other.