Breast tumors may shed cancer cells from the outset, and some of these cells may infiltrate vital organs, including the bones, lungs, and brain. When a tumor is diagnosed and removed, chemotherapy is administered with the goal of eliminating these residual cancer cells. However, metastasis may still emerge in some patients and may take years or decades to occur, suggesting that these cells may not inherently possess - and need some time to acquire - all of the molecular characteristics needed to metastasize.

According to the study, nearly one-third of cases of breast cancer relapse emerge three or more years after diagnosis, with some cases developing decades later. At present, the major clinical benefits from postoperative drug therapies are observed in the first few years after treatment, which may mean that latent cancer cells are at least partially resistant to conventional therapy.

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