Evolution of sub-clinical metastases in breast cancer

12024 Some early stage breast cancer patients bear sub-clinical nodal and/or distant metastases. After primary extirpation, the proportion of failure is lower than would be expected in non-dissected axilla patients and in bone marrow biopsy positive patients. This meant that only some sub-clinical metastases progressed. Since tumor cells continually immigrate into distant or regional sites, but this stops after surgery, progression vs. extinction depends on the unlimited self renewal capability of the resident cells. In turn, this suggested a role for stem cells, specifically their number and character. The number of stem cells in a sub-clinical metastatic focus (regional or distant) can vary considerably from as few as single digits to a hundred thousand. The variation depended on both the size of the tumor at the time of metastatic transformation vs. time of surgery and on the self renewal probability of resident stem cells (Psr). The extinction probability of a single stem cell (E) depends on its Psr. ...