Multicentric tumor manifestations of high grade gliomas: independent proliferation or hallmark of extensive disease?

OBJECTIVE Improvements in microneurosurgical techniques, radiotherapy and chemotherapy for the treatment of high grade gliomas resulted in better local tumor control and longer progression-free survival. Multicentric (MC) lesions located distant from the initial resection area contribute to treatment failure in a growing number of patients. These MC lesions may develop within the course of the disease (metachronous) or may already be present at the time of first tumor manifestation (synchronous). To look for mechanisms and regular patterns behind MC glioma manifestations and to investigate whether they are "a second primary tumor" or the result of continuous diffuse glioblastoma cell invasion, we retrospectively analyzed the initial and all follow-up MR studies of our high grade glioma (HGG) patients. PATIENTS AND METHODS MR studies of 247 consecutive patients treated for HGG at a single institution were analyzed. MC tumor manifestation was defined as more than one gadolinium enhancing lesion within the brain on MRI without a connecting signal alteration in T2 sequences and/or without a connecting hypointense mass in T1 sequences. The minimal distance to define two solitary lesions was set at >10 mm. According to these specifications 40 patients showed MC tumor manifestations in their MR studies on admission or during treatment of their disease. The MR studies of these cases were retrospectively analyzed for patterns in MC tumor manifestation and progression. Topographical specifications and delay in manifestation were used to explain possible pathways of development. Kaplan Meyer survival graphs for metachronous and synchronous MC disease were calculated. RESULTS 24 patients showed MC tumor manifestation at the time of admission. 16 cases developed MC manifestation within a follow-up period of 3-57 months. The location of all lesions could be categorized into one of three distinct patterns (white matter, subependymal, intraventricular). The patterns showed individual and location-specific time gaps to metachronous manifestation. Calculated from the time of first tumor diagnosis, the median survival was longer for patients with metachronous MC lesions (353 days, p<0.05) compared to patients with synchronous MC lesions (110 days) or patients without multicentricity (234 days). Patients with metachronous lesions showed a similar survival (72 days) as patients with synchronous MC lesions (110 days) once they developed MC disease. CONCLUSION The topographical patterns and temporal characteristics of MC disease suggest that all manifestations share common mechanisms such as an active migratory process. Our data therefore do not support the concept of an independent MC development of multiple gliomas.