Introduction: Recent studies suggest poor local control rates and increased risk of radiation necrosis following stereotactic radiosurgery (SRS) in patients with large intracranial metastases. Here, we reviewed our experience with the treatment of large metastatic brain lesions and post-operative cavities using a uniform frameless fractionated regimen (fSRS).
Methods: A retrospective analysis was performed for patients with large (>2.5 cm) intracranial metastatic lesions or post-surgical cavities treated with 5-fraction frameless SRS (30 Gy) using a Novalis linear accelerator over a 6-year period (2009-15). Patient outcomes, including survival, local control, distant failure, and rates of radiation necrosis were recorded.
Results: We reviewed 100 patients with 104 metastatic lesions. Of these, 51 (49%) were post-operative cavities with a median volume of 15.6 cc (IQR 11.3-26.7cc) and 53 (51%) were metastatic tumors with a median volume of 7.2 cc (IQR 5.7-13.9 cc). The most common primary pathologies were non-small cell lung cancer (50.0%), melanoma (15.4%), breast cancer (14.4%), renal cell carcinoma (6.7%), and colon cancer (4.8%). Median survival was 8 months (IQR 3-17), with improved survival in patients undergoing resection prior to fSRS (13 months (IQR 4-20) vs. 6 months (IQR 2.75-12)). Local tumor control was observed in 89.5% of lesions at 6 months post fSRS, and in 83.7% at 12 months. Distant failure was recorded in 24.0% of patients at 6 months and 34.6% of patients at 12 months. Notably, patients who underwent pre-fSRS resection more than twice as likely to develop distant failure (47.1% vs 22.6%; p=0.013). Finally, 9 patients (9.0%) developed symptomatic radiation necrosis with a median interval of 7 months from treatment.
Conclusions: The treatment of large metastatic tumors and surgical cavities with a uniform hypofractionation regimen of 30 Gy in 5-fractions achieves an excellent local control rate (>80% at 12 months) with low risk of radiation necrosis (<10%).
Patient Care: Our retrospective analysis may help support a standardized fractionation protocol for large cerebral metastases, and may further define the role of surgical resection in the treatment of these tumors.
Learning Objectives: By the conclusion of this session, participants should be able to 1) describe the primary challenges in the application of SRS to large metastatic intracranial lesions 2) understand the potential of hypofractionated regimens in the management these large lesions.