WHAT IS SYSTEMIC THERAPY
Local therapies, such as surgery and radiation therapy treat the breast area only. Therapies called “systemic” treat your entire body.
Your MRIs, CTs, PET scans and blood tests came back “normal”, indicating that there are no obvious signs of tumor spread to other parts of your body. So why would you need any therapy in addition to the surgery?
The problem with cancer is that it can metastasize: as the tumor grows, cancer cells can break away and travel down blood vessels or lymph ducts to other parts of the body—much the same way as seeds from a weed are carried away by the wind, or float down a river, to sprout somewhere else.
In the very early stages, these groups of break-away cells, called micrometastases, are very small, and cannot be found by any test or method that exists today. But if one waits until these tiny cancerous clumps grow into larger tumors that can be confirmed by X-rays or CT scans, then successful treatment becomes difficult.
Because of this, many clinicians recommend treatment with adjuvant, or additional therapy such as chemotherapy or hormonal therapy, or both, whenever there is a reasonable chance that cancer cells have metastasized to other parts of the body. The reasoning is that while hormone therapy and chemotherapy may be unpleasant, cancer recurrences can be life-threatening. Therefore the benefits outweigh the side effects.