NCOG-25. REVISITING THE PIGNATTI RISK SCORE IN LOW-GRADE GLIOMA PATIENTS IN THE MOLECULAR ERA

Abstract

Abstract Until now, the Pignatti risk score has been used to guide treatment decisions after histological diagnosis of diffuse glioma WHO grade 2. However, its prognostic value was derived from a historic cohort that has been diagnosed by morphologic rather than molecular criteria. We re-challenged the Pignatti score in a contemporary, molecularly characterized cohort. From our institutional cohort of 422 diffuse gliomas WHO grade 2, 202 patients were identified for whom IDH mutation status was known and 1p/19q co-deletion or loss of ATRX expression unambiguously classified tumors into astrocytoma or oligodendroglioma. Patients with IDH wildtype astrocytoma (n=9), multifocal lesions or brainstem involvement were excluded. Potential prognostic factors including the individual items of the Pignatti score (astrocytoma; age ≥40 years; neurologic deficit; maximum tumor diameter ≥6cm; tumor crossing midline) were correlated with progression-free survival (PFS) by univariate log-rank und multivariate Cox regression analysis. 165 patients with astrocytoma or oligodendroglioma were analysed of whom 109 (66%) did not receive adjuvant radio- or chemotherapy. 94 untreated patients with a minimum follow-up of 24 months entered survival analysis. These patients were classified as “high-risk” (Pignatti 3-5) and “low-risk” (Pignatti 0-2) in 15% and 85% and did not differ with regard to potential prognostic factors (gender; resection vs. biopsy; tumor recurrence) other than the individual Pignatti score items. Diameter ≥6 cm (p=0.006; HR=2.18) and midline crossing (p=0.003; HR=3.54) were identified as independent prognostic factors of PFS. Noteworthy, prognostic factors coincided when all patients (n=144) with a minimum follow-up of 24 months, regardless of adjuvant treatment, were analysed. In IDH mutant, molecularly characterized diffuse gliomas WHO grade 2, the Pignatti risk score as a whole no longer seems to be of prognostic relevance. Instead, outcome seems to be determined by tumor burden.