Use of the international prognostic index and the tumor score to detect poor-risk patients with primary mediastinal large B-cell lymphoma: a study of 37 previously untreated patients.

We tested two prognostic models devised for intermediate-grade lymphomas, the age-adjusted international prognostic index and the tumor score, in 37 consecutive untreated patients treated for a diagnosis of primary mediastinal large B-cell lymphoma (PMLCL). Neither model selected for a group of patients with statistically significant differences in rates of complete response, failure-free survival (FFS) and overall survival (OS). Because the level of beta microglobulin (beta2m) is consistently low in the serum of patients with PMLCL despite bulky disease, we tested the median value of this continuous variable in the 37 patients and found it to be statistically significant for predicting FFS. A hypothetical tumor score model using the adjusted value for beta2m improved the prognostic accuracy for achievement of complete response (93% vs. 60%; P = 0.02), FFS (73% vs. 35%; P = 0.02), and OS (80% vs. 55%; P = 0.05). This hypothetical model merits further testing in a larger population of patients with PMLCL.