gms | German Medical Science

Objective: Both, intraoperative MRI (iMRI) and 5-ALA fluorescence represent appropriate means to maximize extent of resection in brain tumor surgery. Our aim was to report on the surgical outcome of using both modalities in the surgical treatment of patients with suspected malignant gliomas.

Method: 50 patients with contrast enhancing lesions suspected to be a malignant glioma scheduled for microsurgical resection were prospectively included in this analysis. All patients received 20mg/kg bodyweight 5-ALA prior to surgery. Surgeries were conducted with the use of an intraoperative MRI. Tumor resections were performed under white light conditions until the surgeon was convinced to have resected the intended amount of tissue, before an intraoperative MRI scan was obtained and blue light subsequently turned on. All patients had detailed histopathological assessment of tumor specimens and received early postoperative MRI to determine the extent of resection. Complete resection was defined as absence of residual contrast enhancement. All patients had adjuvant treatment according to histology. Ethics committee approval was obtained for this study.

Results: Intraoperative MRI revealed residual contrast enhancing tissue in 20 cases (40%). Under blue light, residual fluorescent tissue was visible in 17 patients (34%). Complete tumor resection was achieved in 39 patients (78%). All additionally resected tissue specimens were positive for pathological tissue; both modalities were consistent in indicating presence or absence of residual tumor in only 11 (22%) and 13 (26%) cases, respectively. Histology revealed glioblastoma in 37 patients (74%), 13 patients (26%) suffered from other entities (e.g., WHO grade III gliomas or metastases). Kaplan Meier analysis rendered a median overall survival of 18.8 months for patients with glioblastomas, and 31.4 months for other patients. The rate of new neurological deficits was within acceptable limits (12%), and only 2 patients (4%) experienced severe deficits with long-term decline of KPS score.

Conclusions: 5-ALA fluorescence and iMRI represent valuable surgical tools that are not exclusive but supplementary in terms of detection of unintentionally remaining tissue. Given the fact that preoperative diagnostics cannot predict tumor histology, combined use of these modalities is justified for patients with contrast enhancing lesions, leading to best possible surgical results.