PROGNOSTIC FACTORS (PFs) IN PRIMARY MEDIASTINAL LARGE B‐CELL LYMPHOMA (PMLBCL) TREATED WITH RITUXIMAB‐CHOP (RCHOP) ± RADIOTHERAPY (RT)

Introduction: RCHOP provides satisfactory results in PMLBCL, minimizing failure rates, but PFs have not been sufficiently evaluated, since only 2 moderately-sized studies have appeared so far including 96 and 123 patients (pts) from British Columbia and Japan, respectively. In the presence of R-da-EPOCH, a potentially better but also more toxic regimen compared to RCHOP, a reliable prognostic classification of PMLBCL is urgently needed, in order to define subgroups of pts at high- or very low-risk for treatment failure and death. Aims: The identification of PFs for the outcome of pts with PMLBCL treated with RCHOP±RT. Methods: 325 pts with PMLBCL ≤65 years old were treated with RCHOP±RT (usually 6-8 cycles) in a multicenter setting in Greece and Cyprus. The following potential PFs were evaluated: Age (median 32; range 16-65), gender (female 65%), B-symptoms (32%), stage III/IV (14%), infradiaphragmatic disease (10%), any extranodal involvement (E/IV, 37%), any serositis (45%), bulky disease (≥10 cm; 63%), performance status (PS) ≥2 (14%), LDH levels (elevated 83%; ≥2x, 27%), anemia (38%), leukocytosis ≥10x109/L (26%), ESR ≥50 mm/h (39%), albumin <4 g/dL (46%), age-adjusted IPI (aaIPI; ≥2 in 22%). Results: At amedian follow-up of 64 months (2-198), 68 failures and 34 deaths were recorded (including 2 unrelated deaths) for a 5-yearfreedom from progression (FFP) of78% and both 5-year overall survival (OS) and lymphoma specific survival (LSS) of 89%. The aaIPI was moderately predictive with 5-year FFP of 82% vs. 71% for aaIPI 0-1 vs 2-3 (p = 0.04). On univariate analysis, extranodal involvement (E/IV), bulky disease, and low albumin were significantly associated with both inferior FFP and LSS, infradiaphragmatic disease and LDH ≥2x only with FFP, while any serositis and anemia only with LSS. The results of multivariate analysis and the respective prognostic models are shown in the table. Conclusions: In the largest pt series with PMLBCL reported so far, RCHOP±RT provided long-term disease control and LSS rates of 78% and 89%. The combination of any extranodal involvement (E/IV) with either bulky disease or LDH ≥2x defined high-risk subgroups (13-27% of pts) with ~20-23% mortality. More importantly, their absence defined subgroups comprising ~1/4 or 1/2 of the pts, with 10-11% risk of failure and only 1.5% or 3.5% 5-year mortality, who might not benefit from intensified treatment as R-da-EPOCH. Keywords: primary mediastinal large B-cell lymphoma (PMLBCL); prognostic indices.