Peripheral T-Cell Lymphoma, Not Otherwise Specified: A Clinicopathologic Study of 340 Cases from the International T-Cell Lymphoma Project.

Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), is an uncommon lymphoma in which the clinical and pathological features of prognostic importance are not well understood. Therefore, we collected 340 cases of PTCL-NOS from 21 centers in 13 countries around the world to study this entity. PTCL-NOS was the most common subtype of PTCL in the project (29.3%) and consisted mainly of PTCL unspecified (88.5%) and the lymphoepithelial type (8.2%). The median age of the patients was 60 years, 66% were males, and 69% had stage III/IV disease at diagnosis. Anthracycline-based chemotherapy was given in 80% and a complete response was obtained in 56% of the patients. However, the 5-year overall and failure-free survivals for the entire group were only 32% and 20%, respectively. The International Prognostic Index (IPI) was highly predictive of survival (p<0.001). Other clinical prognostic factors identified in multivariate analysis (MVA) included hypergammaglobulinemia (HR 0.5), mass >10 cm (HR 2.5), and platelets <150,000/mm³ (HR 2.2). Pathologic features predictive of survival included >70% transformed cells (HR 1.7) and <10% CD8+ background T-cells (HR 1.8). However, in final MVA, only the IPI and >70% transformed cells were predictive of survival. In conclusion, PTCL-NOS is an aggressive disease in which the IPI and the percentage of transformed cells could be used to select patients for risk-adapted therapies.