IELSG Prognostic Score for Primary CNS Lymphoma
The IELSG (International Extranodal Lymphoma Study Group) prognostic score is a validated five-factor scoring system that assigns 1 point for each adverse feature: age >60 years, ECOG performance status >1, elevated serum LDH, elevated CSF protein concentration, and involvement of deep brain structures (periventricular regions, basal ganglia, brainstem, or cerebellum). 1
Score Components and Point Assignment
The scoring system is straightforward—each variable receives either 0 (favorable) or 1 (unfavorable) point 2:
- Age >60 years = 1 point
- Performance status >1 = 1 point
- Elevated serum LDH = 1 point
- High CSF protein concentration = 1 point
- Deep brain structure involvement = 1 point
Total scores range from 0-5 points.
Risk Stratification and Survival Outcomes
The original IELSG validation demonstrated clear prognostic separation 2:
- Low risk (0-1 points): 2-year overall survival 80%
- Intermediate risk (2-3 points): 2-year overall survival 48%
- High risk (4-5 points): 2-year overall survival 15%
This stratification remained significant even when limited to patients receiving high-dose methotrexate-based chemotherapy (2-year OS: 85%, 57%, and 24% respectively) 2.
Current Clinical Context and Limitations
While the 2024 EHA-ESMO guidelines acknowledge the IELSG score alongside the Memorial Sloan Kettering Cancer Center score 1, recent evidence reveals important limitations in the era of intensified treatment regimens. The IELSG score's discriminatory power has been questioned in contemporary cohorts receiving modern therapy including consolidative high-dose chemotherapy with autologous stem cell transplantation 3, 4.
Key Caveats:
- The IELSG score may require dichotomization (scores <2 vs ≥2) rather than the original three-tier system to maintain prognostic value in some populations 3
- The three-factor (3F) score has demonstrated superior concordance (C-index 0.71) compared to IELSG (C-index 0.53) in patients receiving intensified regimens 4
- Modified IELSG scores with adjusted cutoffs (e.g., age ≥54 years, LDH/ULN >0.75) may improve performance in specific populations 5
Practical Application
Despite these limitations, the IELSG score remains clinically useful for initial risk assessment at diagnosis. However, age remains the dominant prognostic factor 1, and treatment stratification should not rely on age alone but incorporate performance status, organ function (creatinine clearance >50 mL/min, LVEF >45%), comorbidities, and frailty 1.
For immunodeficiency-associated PCNSL, the IELSG score performs poorly—a disease-specific model incorporating age, KPS <70, and EBV positivity provides superior stratification 6.
The IELSG score should be calculated at baseline for all immunocompetent PCNSL patients but interpreted cautiously in treatment planning, particularly for patients receiving modern intensive regimens where other factors may better predict outcomes.