Background Adult low-grade gliomas (LGG) are usually WHO grade II and have a propensity to transform into malignant gliomas at some point in their natural history. Prognostic factors for patients treated with radiotherapy include increasing age and tumour diameter, but may not be applicable to patients who have not received any oncological treatment. We have carried out a prospective multimodality imaging study of 47 untreated adult patients with supratentorial LGG to determine which factors are independently associated with a poor prognosis, using time to progression as the primary endpoint.

Methods Patients were recruited from the neuro-oncology clinic and followed up from January 1999 to December 2006. Baseline clinical and radiological data were collected and Kaplan–Meier, univariate and multivariate analysis using Cox proportional hazards regression model, were carried out.

Results 28 patients (60%) had progressed by the end of the study. Median progression-free survival was 35.4 (9.9–93.3) months. In univariate analysis, 6 out of 12 prognostic variables reached significance at the 10% level. Multivariate analysis showed that only baseline tumour volume as well as lead time between first seizure and first MRI study were significant at the 5% level.

Conclusions Tumour volume, measured with an easily reproducible method on standard MR sequences, is of prognostic value in predicting tumour progression in patients with untreated LGG.