Epidemiological and Clinico-Pathological Features of Systemic Peripheral T-Cell Lymphomas (PTCL): A Population-Based Analysis from the Danish Lymphoma Registry LYFO

PTCL are a heterogeneous group of uncommon lymphoid malignancies. Geographical differences have been reported, the NK/T-cell-derived nasal type being more common in Asia and the entheropathy-type more common in western countries. Except for the alk-positive anaplastic large cell lymphoma (ALCL) subtype, PTCL have generally a poorer outcome than their B-cell counterparts when treated with conventional therapeutic strategies. In recent years, as a result of an improved biologic understanding and definition of PTCL entities, an increasing number of PTCL-specific clinical trials have been initiated. The purpose of this analysis was to describe epidemiological and clinico-pathological features of the major subtypes in PTCL, as they occur in an unselected western population, in order to provide population-based data that may be useful for the design of future PTCL-specific studies. Although the LYFO registry was initiated in 1983, the present analysis only includes patients diagnosed in the 15-year period from 1990 (when immunhistochemistry was routinely applied to all biopsy specimen) to 2004. Within this 15 yr period, 485 PTCL cases were diagnosed. They had an age range of 16–92 yrs and a male to female ratio of 1.4 (59% male and 41% female cases). The most frequent histological subtypes were PTCL unspecified (PTCLu) (44%), non-cutaneous ALCL (alk-status not available) (35%) and angioimmunoblastic (AIL) (17%). The incidence trend for PTCL, taken as one group, did not show significant changes over the 15 years observation period. Approximately two thirds of the patients (65%) had disseminated disease (stage III–IV) at diagnosis, while half of the patients (49%) presented with B-symptoms. AIL had a higher frequency of cases with disseminated disease (93%, p<0.05), mainly due to bone marrow involvement, while ALCL had a significantly higher frequency of localized cases (46%, p<0.05). Surprisingly, the majority of PTCL patients (69%) were registered at diagnosis with a good performance score (WHO) of 0–1, with figures for PTCLu and ALCL of 65% and 69%, respectively, and slightly lower (52%, p>0.05) for AIL. All three major subtypes had predominantly nodal disease at presentation (PTCLu 56%, ALCL 57%, AIL 61%). Pre-therapeutic s-LDH was elevated in 40 % of all PTCL patients (PTCLu 44%, ALCL 39%). AIL cases presented more often with elevated s-LDH (61% of the cases, p<0.05). In line with these findings, AIL also had a higher frequency of cases with IPI ≥2, which translated into an inferior 5-yr overall survival value (25%, as opposed to 33% and 39% for PTCLu and ALCL, respectively). These survival values represent the comparative background on which the potential impact of the new PTCL trial program of our nordic collaborative group will be evaluated.