Dynamic prognostication using conditional survival estimates
Measures of prognosis are typically estimated from the time of diagnosis. However, these estimates become less relevant as the time from diagnosis increases for a patient. Conditional survival measures the probability that a cancer patient will survive some additional number of years, given that the patient has already survived for a certain number of years. In the current study, the authors analyzed data regarding patients with stage III melanoma to demonstrate that survival estimates from the time of diagnosis underestimate long-term survival as the patient is followed over time. The probability of surviving to year 5 for patients at the time of presentation compared with patients who had already survived for 4 years increased from 72% to 95%, 48% to 90%, and 29% to 86%, respectively, for patients with substage IIIA, IIIB, and IIIC disease. Considering the major role played by survival estimates during follow-up in patient counseling and the development of survivorship programs, the authors strongly recommend the routine use of conditional survival estimates.