Realistically, the only way is to wait for 20 years and make sure the tumor does not come back. Obviously, this is not practical. Instead, certain factors that put a patient at high risk can be estimated and the probability of cure determined. The appearance of the tumor under the microscope is the next best predictor. However, one cannot be completely certain whether an individual patient has been cured or not.
Tumors can appear again, which is called recurrence.
Most of the recurrences are seen during the first three years. After three years, the rate of recurrence per year can be determined, and this is called a hazard rate. This is how physicians predict that women are probably cured. Yet one cannot be certain, because some women may have a relapse, even after 13 years. Similar considerations are used to predict the possibility of cure in women with larger tumors and with lymph node involvement.