Conditional survival of patients with diffuse large B-cell lymphoma.

BACKGROUND: Prognosis of lymphoma patients is usually estimated at the time of diagnosis and the estimates are guided by the International Prognostic Index (IPI). However, conditional survival estimates are more informative clinically, as they consider those patients only who have already survived a period of time after treatment. Conditional survival data have not been reported for lymphoma patients.
METHODS: Conditional survival was estimated for 1209 patients with diffuse large B-cell lymphoma (DLBCL) from the population-based LYFO registry of the Danish Lymphoma Group. The Kaplan-Meier method was used to estimate conditional survival at 0-5 years after diagnosis.
RESULTS: The probability of surviving 5 years increases with each year survived for the first 3 years after diagnosis, after which the increase is minimal. The median survival increases from 38 months for all patients to between 108 and 120 months, conditioned on survival for at least 3-5 years. The prognostic capacity of the IPI and the age-adjusted IPI was high at diagnosis, but the significance gradually declined in the first years after diagnosis. Furthermore, the prognostic impact of the individual clinical variables of the IPI was also significant at diagnosis, but 2 years after diagnosis only age had prognostic impact. Multivariate analysis of patients who survived > or = 3 years identified only age as a prognostic factor.
CONCLUSION: For patients with DLBCL who have survived more than 1 year after diagnosis, the conditional survival probability provides more accurate prognostic information than the conventional survival rate estimated from the time of diagnosis. Copyright 2006 American Cancer Society