gms | German Medical Science

Objective: Microsurgical, circumferential stripping of cerebral metastases from the surrounding brain tissue often proves to be insufficient to prevent local recurrences. For malignant gliomas, 5-ALA derived fluorescence guided surgery (FGS) has drastically improved the rate of complete resections. Since 5-aminolevulinic acid (ALA)-derived fluorescence has been reported for various carcinomas outside the CNS, we analyzed 5-ALA-derived fluorescence of cerebral metastasis and the feasibility of this method in detecting residual tumor.

Methods: A retrospective analysis was performed for 36 patients who underwent 5-ALA-derived fluorescence-guided surgery for an assumed malignant glioma and in whom the intraoperative diagnosis was corrected to a cerebral metastasis. ALA-fluorescence was documented for all metastasis as well as for the tumor-bed and data were correlated to the results of the histopathological analysis and the postoperative MRI. Tumor bed was evaluated for residual fluorescence and biopsies were taken from normal appearing fluorescent positive adjacent tissue and suspected

Results: Intraoperatively, 26/36 metastases showed an ALA-derived fluorescence, whereas 10 were ALA-negative. Residual fluorescence of the normal appearing tumor bed was detected after “complete” white light resection for 14/36 patients. Here, presence of tumor was confirmed histopathologically in nearly 60%. Histopathologically, analysis of the tumor-brain interface (n=30) revealed a sharp delimitation in only 27% of metastases, whereas 41,6% expanded conically into the adjacent brain tissue and 14% demonstrated an infiltrative growth pattern. Determination of characteristic tumor markers and further tumor staging revealed the following primary tumors: non-small bronchial carcinoma (n=21), breast cancer (n=5), colorectal carcinomas, renal cancer (each n=3), malignant melanoma (n=2), esophageal- and ovarian carcinoma (n=1, respectively).

Conclusions: In most cases cerebral metastases were not sharply demarcated. Furthermore, the macroscopically normal appearing but fluorescent tumor bed showed histological evidence of residual tumor in more than 50%. Thus, ALA-fluorescent guided resection may facilitate a more complete resection of cerebral metastases. Further studies investigating the impact of fluorescence-guided resection of cerebral metastasis are needed.