The theory of angiogenesis originated from Judah Folkman, who in 1971 proposed that, once a nest of cancer cells reaches a certain size (1-2 mm in diameter), it must develop its own blood supply in order to grow larger. Diffusion is no longer adequate to supply the cells with oxygen and nutrients and to take away wastes.
A recent analysis of breast-cancer relapse patterns from two independent databases provides give reasons to believe that surgery to remove the primary tumor in fact initiate angiogenesis in previously sleeping metastases cancer cells. This may, as per this theory, account for a pattern of early relapse in younger women.
This provoking study was published in the online issue of International Journal of Surgery. The study comes from analysis 1,173 women who were included in three separate clinical trials and who had surgery for breast cancer, but no further treatment. The researchers have found two relapse peaks in these women: one at 18 months from surgery, and another at 5 years. Closer analysis showed that 20 percent of pre-menopausal, node-positive patients (whose cancer had spread to the lymph nodes) relapsed within the first 10 months after removal of the primary tumor.
The researchers, led by Michael Retsky, PhD, think that the early peak in recurrence is due to stimulation of dormant cells, by angiogenesis. The study did not look at biological mechanisms of relapse, but this argument is based on the fact that primary tumors have been shown to secrete angiogenesis inhibitors, which naturally inhibit the growth of metastases, so surgery to remove the primary tumor might eliminate this inhibition. Alternatively, surgery might spur release of angiogenesis promoters through a wound-healing mechanis. |
