Authors: Arthur Carminucci, MD; Sabrina Zeller, BS; Shabbar Danish, MD (Newark, NJ)

Introduction: Recurrence following Gamma Knife (GK) radiosurgery treatment of cerebral metastases is not uncommon. Recurrence can represent recurrent tumor or radiation necrosis. The radiographic response to GK treatment is variable with some tumors remaining stable, some decreasing in size, some increasing in size, while some may show a combination of all three. For recurrences, which demonstrate progression on MRI imaging, the question to intervene with additional surgical or radiation therapy and the timing of such intervention is debatable. In this this study, we retrospectively reviewed surveillance MRIs of post-GK cerebral metastases to determine if radiographic trends are a predictor of infield progression. Methods: Retrospective review of cerebral metastases treated with GK radiosurgery with atleast 2 consecutive post-GK MRI scans. Results: 297 cerebral metastases were treated with GK radiosurgery. Median length of follow-up was 21 months (3-105.2). Local control rate 82.5%. Sixty-nine metastasis demonstrated radiographic progression on 1 follow-up MRI scan. Of those 52 (75.4%) demonstrated continued progression and/or need for surgical intervention on follow-up imaging, while 17 (27.9%) stabilized or regressed. For post-GK metastases demonstrating progression on two consecutive MRI scans, 87.8% (n=36) of lesions continued to progress; whereas; only 12.2% (n=5) demonstrated stabilization or regression. 100% (n=28) of metastasis with radiographic progression on 3+ consecutive MRIs went on to need further intervention. Conclusion: Approximately, one third of post-gk metastasis demonstrating progression on the first surveillance MRI will stabilize or regress. However once radiographic progression is demonstrated on 2 consecutive scans, 87.8% will ultimately progress; suggesting need for further intervention at this time point. Early intervention before infield recurrence increases in size or patients require high-dose steroids maybe beneficial.
Leksell Radiosurgery Award