Metabolic tumor volume as an independent prognostic factor in lymphoma

Abstract

6594 Background: In Hodgkin’s disease (HD) and aggressive non-Hodgkin’s lymphomas (NHL), well-established clinical and laboratory parameters–the international prognostic factors (IPF) for HD and international prognostic index (IPI) for NHL–have been shown to have important prognostic value. While unidimensional measures of tumor size have not been independently predictive in these analyses, tumor burden is of recognized clinical importance. Our aim was to determine whether total body metabolic tumor volume (MTV) on FDG-PET independently predicts the likelihood of relapse for HD and aggressive NHL. Methods: We retrospectively analyzed 98 patients treated over the past two years at our institution for classical HD (n=46) and aggressive NHL (n=52) who had initial staging PET-CT scans. Average post-treatment follow-up time was 12.3 months, with disease relapse as the endpoint (17/46 for HD, 21/52 for NHL). No patients were lost to follow-up. Potential predictor variables including age, gender, stage, and IPI or IPF were identified for each patient. We also measured pre-treatment total MTV in milliliters using our own semi-automated image analysis software. Continuous variables (age, MTV) were compared using the Student’s t test, and categoric variables (gender, stage, IPI and IPF) were compared using Fisher’s exact test. IPI was categorized as low (0–1), intermediate (2–3) and high (4–5) risk, and IPF as favorable (less than 3) or unfavorable (3 or more). A univariate logistic regression was performed for each potential predictive variable, yielding odds ratios for relapse vs. non-relapse. A stepwise multivariate logistic regression was then performed to identify true independent predictors of relapse. Results: In the univariate analysis, stage (OR=1.06, 95% CI = 1.00–1.10, p=0.045), IPI (OR=1.13, 95% CI = 1.07–1.18, p=0.032), IPF (OR=1.08, 95% CI = 1.02–1.12, p=0.040) and MTV (OR=1.09, 95% CI = 1.04–1.15, p=0.021) proved to be significant predictors of relapse, but not age or gender. In the multivariate analysis, only MTV, IPI and IPF were independently predictive of relapse. Conclusions: MTV appears to have prognostic significance for early relapse in both classical HD and aggressive NHL independent of the standard prognostic indices. No significant financial relationships to disclose.