A question that I am often asked is Do I Need Chemotherapy? Or why does anyone need chemotherapy? The answer is: Because chemotherapy kills cancer.
What is chemotherapy? Chemotherapy is medicine that kills cancer cells by disrupting their growth. Chemotherapy is not very specific. Chemotherapy also kills healthy cells and that is why there are many side effects, but chemotherapy can be effective. It works by attacking those breast cancer cells that have escaped the breast and are hiding out in the bones, the liver, or maybe the lungs and kills them before they can grow.
Since chemotherapy has some pretty nasty side effects, it would be helpful to identify those women who have low risk tumors and do not need chemotherapy from those who have a high risk tumor and need chemotherapy. Tumors larger than 2cm are at increased risk for having tumor cells that have escaped the breast as are tumors that have already spread to the axillary lymph nodes, i.e. “node positive” disease.
Still, the biology of the tumor is what really determines the need for chemotherapy. Those tumors with worse biology will be those that grow bigger and spread to the lymph nodes, and this is the reason the AJCC-TNM staging system is prognostic. But tumors with less aggressive biology can still grow large if given enough time and very aggressive tumors can be quite small if caught early. So, is there a way to identify the biology of the tumor without looking at the size and nodal status of the tumor? Yes. OncoType Dx is a test that can separate those tumors likely to respond to chemotherapy from those tumors least likely to respond to chemotherapy.
Do I need chemotherapy? Women with tumors greater than 2cm or with positive lymph nodes probably need chemotherapy. Women with tumors less than 1cm most likely do not need chemotherapy. And women with tumors between 1-2cm should have OncoTypeDx test performed to see if they need chemotherapy.