TUMOR SEEDING FOLLOWING STEREOTAXIC BIOPSY OF BRAIN METASTASES - REPORT OF 2 CASES

In a series of 22 patients heated with gamma knife surgery for brain m etastasis in whom biopsy specimens were obtained via stereotactically guided procedures before the radiosurgical treatment was administered, two cases with evidence of tumor seeding were observed on subsequent follow-up examination. These findings contradict the opinion that the risk for tumor spread after a biopsy is negligible. This evidence may be explained by the fact that radiosurgery leaves the surrounding tiss ue unaffected by the treatment, which results in preserved anatomy aro und the tumor. This allows the surgeon to define the previous biopsy c hannel and, consequently, whether a distant tumor recurrence may have resulted from tumor seeding related to the biopsy procedure. Additiona lly, radiosurgical treatment leaves tumor cells that may have been spr ead as a result of the biopsy unaffected, giving them the potential to divide and develop into a new tumor. In contrast to this, microsurgic al removal of the tumor will affect the surrounding tissue, making it impossible to detect whether new metastases are resulting from seeding . Furthermore, conventional fractionated radiation therapy will steril ize tumor cells that may have spread, thus making it impossible for th ese cells to regrow. The authors conclude that the risk for tumor seed ing following a stereotactically guided biopsy may be higher than prev iously assumed.