The conditional survival statistics for survivors with primary supratentorial astrocytic tumors

Relative survival rates can offer a general description of tumor outcome and, traditionally, are used for surveillance and comparison purposes. However, they are not informative for individual tumor survivors. Conditional survival estimates can calculate the probability of surviving next some years given survival to a specific period of time after craniotomy for individual tumor survivors. However, clinically, they have not been used for predicting the tumor outcome. We calculated conditional probabilities of survival within 6 years after craniotomy in 112 patients with primary supratentorial astrocytic tumors and evaluated factors affecting the survival time more than 2 years after craniotomy. Our data showed that the conditional probability of survival can predict yearly survival rate when patients survive for a specific period of time. The conditional survival rates within 6 years after craniotomy were always higher than those evaluated by relative survival rates. Overall, the longer the patients survived, the higher the conditional probabilities of surviving sixth year postoperatively were. Our study demonstrates the conditional probabilities of survival have good availability and are important estimates for individual tumor survivors.