gms | German Medical Science

Objective: Until now, the Pignatti risk score has been used to guide treatment decisions after histological diagnosis of diffuse glioma WHO grade II. However, its prognostic value was derived from a historic cohort of gliomas that has been diagnosed by morphologic rather than molecular criteria. Thus, we sought to challenge the Pignatti score in a contemporary, molecularly characterized cohort.

Methods: From our institutional cohort of 422 diffuse gliomas WHO grade II, 202 patients were identified for whom IDH mutation status was known and either 1p/19q co-deletion or loss of ATRX expression unambiguously classified tumours into astrocytoma or oligodendroglioma. Patients with multifocal lesions, brainstem involvement, impossible follow-up or lack of pre-operative MRI were excluded. Potential prognostic factors including the individual items of the Pignatti score (astrocytoma; age ≥40 years; neurologic deficit; maximum tumour diameter ≥6cm; tumour crossing the midline) were correlated with progression-free survival (PFS) by univariate log-rank und multivariate Cox regression analysis.

Results: 174 patients with astrocytoma or oligodendroglioma were analysed of whom 114 (66%) had not received adjuvant radio- or chemotherapy. 99 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% of cases and did not differ in terms of potential prognostic factors (sex; resection vs. biopsy; tumour recurrence; IDH mutation status) other than the individual Pignatti score items. Diameter <6 cm (p<0.0001), no midline crossing (p<0.0001), “low-risk” Pignatti score (p<0.001), resection rather than biopsy (p=0.012) and presence of IDH mutation (p=0.003) significantly prolonged PFS in univariate analysis. Diameter <6 cm (HR 1.86; p=0.03), no midline crossing (HR 4.49; p=0.006), resection (HR 0.42; p=0.009) and IDH mutation (HR 0.36; p=0.041) were identified as independent prognostic factors of superior PFS in this cohort. Noteworthy, prognostic factors coincided when all patients (n=153) with a minimum follow-up of 24 months, regardless of adjuvant treatment, were analysed.

Conclusion: In molecularly characterized, untreated diffuse gliomas WHO grade II, the Pignatti risk score as a whole no longer seems to be of prognostic relevance. Instead, outcome seems to be determined by preoperative and postoperative tumour burden and IDH mutation status.