Non-enhancing/minimally enhancing gliomas: can we identify low grade gliomas?

Abstract AIMS Gliomas are traditionally separated into low-grade (LGG) and high-grade (HGG). As LGG are slower growing and with pressures on operating capacity, there is an argument that surgery for these patients can wait. Pre- operatively, contrast enhancement on imaging is usually taken as the method of differentiating grade, with the belief that the absence of enhancement indicates LGG. We therefore assessed patients with minimal/non- enhancing tumours and compared factors at diagnosis with final histological outcome. METHOD We identified a cohort of patients over a 19-month period with a first presentation to the neurosurgical oncology clinic with minimal/patchy/scattered foci of enhancement (ME) or no areas of contrast enhancement (NE) on imaging, collecting factors at diagnosis and histological outcome using electronic patient records. RESULTS Of 60 patients identified, 53.3% were HGG, 35.0% LGG and 11.7% non-glioma. In NE tumours HGG and LGG rates were equal (43.3%), whereas in ME tumours HGG comprised 63.3% versus 26.7% LGG. HGG patients were older on average than LGG (median age 53 years versus 33 years) and more prevalent in males (62.95%) compared to females (45.45%). HGG formed the majority of patients presenting with seizure only (60%), neurological deterioration only (50%) or ≥2 symptoms (57.6%), whereas LGG was higher in presentations with headache only (66.7%) or none of the symptoms (66.7%). CONCLUSIONS It is not possible to differentiate between ‘high-grade’ and ‘low-grade’ gliomas based on imaging findings alone. Age is clearly a differentiating factor, but symptoms do not appear to be. We are working to develop methods to better differentiate these tumours pre-operatively.