Patterns of radiological response to PC polychemotherapy in patients with oligodendroglioma
Sophie Katzendobler, Luis Kuschel, Nicola Zieger, Frederic Thiele, Michael Schmutzer-Sondergeld, Dragan Jankovic, Roman Stürzl, Patrick N Harter, Robert Stahl, Darius Kalasauskas, Asgeir S Jakola, Nathalie L Albert, Emilie Le Rhun, Michael Weller, Florian Ringel, Jonathan WellerAbstract
PURPOSE
To characterize the radiological response to procarbazine and CCNU (PC) polychemotherapy in patients with oligodendroglioma.
METHODS
In this retrospective single-centre cohort study, patients with CNS WHO grade 2 or 3 oligodendroglioma treated with PC between 2003 and 2019 were included. Tumor characteristics were assessed on magnetic resonance imaging (MRI) and [18F]Fluoroethyltyrosine positron emission tomography ([18F]FET PET). before and after completion of PC. The T1/T2 ratio was assessed to characterize diffuse versus sharply delineated MRI phenotype. Progression-free survival (PFS) and overall survival (OS) were analyzed.
RESULTS
Forty-six patients with a median follow-up of 118 months were identified. Median absolute T2 tumor volume was 52 cm³ (range 10–285) prior to PC and 29 cm³ (range 3–286) after. Median tumor volume decrease was −30% (range −96% to + 113%). In treatment-naïve patients, median tumor volume decrease was −41% (range −92% to + 14%) versus −7% (range −96% to + 113%) in pretreated patients (p < 0.01). Stratification according to CNS WHO grade (p = 0.89) or contrast enhancement (p = 0.07) did not yield significant differences. The T1/T2 ratio was lower after PC (0.69 vs 0.50, p = 0.04), and higher T1/T2 ratios were associated with shorter PFS (p = 0.04) in multivariate analysis. On [18F]FET PET, there was a trend towards lower maximum tumor-to-brain ratios (TBRmax) after PC (p = 0.07).
CONCLUSION
PC polychemotherapy induces substantial tumor volume reductions in subsets of patients with oligodendroglioma, particularly in treatment-naïve patients. The observations that circumscript oligodendrogliomas may be associated with earlier progression and that PC treatment may induce a shift toward a more diffuse phenotype require prospective validation.