How do doctors determine what stage cancer is in and how long a patient has to live?
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This varies based on the particular type of cancer.
Melanoma, for instance, is staged based on its depth of invasion. Breast cancer, on the other hand, has a number of factors that we take into consideration.
Generally though it’s based on the “TNM classification” system
* **T** for tumor (how big it is)
* **N** for nodes (whether it’s spread to nodes and, if so, how many nodes or which ones)
* **M** for metastasis (whether it’s spread to other organs). M1 = yes; M0 = no.
A cancer may be written as T1N0M0. For breast cancer, that would mean a cancerous tumor that’s less than 2 cm, which hasn’t spread to any nodes or any other part of the body. This would be considered stage 1. If it has spread to other parts of the body, a cancer is virtually always considered stage 4. But every cancer is staged a little differently. We have charts that we can use to convert TNM definitions to stage.
Stage is mostly important for giving a prognosis (e.g., survival likelihood) and it only loosely relates to treatment. How we treat the patient is based on the size of the tumor, whether it’s spread to nodes, and whether there’s metastasis. One breast cancer could be really small (< 1 cm), but if it’s in the lymph nodes, we always use chemo as part of treatment. But another breast cancer could be large (3 cm+) but if it hasn’t spread to nodes or organs, we can typically just do surgery and radiation.
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