What is 5-year survival?

Why has that become a significant number? It has become a benchmark to measure a treatment’s success. When someone undergoes curative treatment, for various reasons addressed earlier, a fraction of those will eventually relapse. “Adjuvant” treatments are designed to decrease the relapse rate, and hence, increase the cure rate.

But, how can you measure the success of a treatment, when there is no measurable tumor left? This 5-year survival number can measure that. If more patients are alive after 5 years with treatment X versus treatment Y, then X is a better treatment. 5 years was probably picked, because it was a reasonable length of time that patients could be closely monitored for disease recurrence. And if the disease had not relapsed by 5 years, it would be reasonable to consider that it would not, in the future.

In fact, in some cancers, once you get past the 2-year point, the odds start getting dramatically better. In some others, there is a tail that extends to the 7-10 year point.

After curative treatment, patients wonder, at what point can they  consider themselves to be cancer free? I like to think that they are cancer free after they finish their initial treatment. There is no disease to measure. So, let us consider it gone.