Preoperative Stereotactic Radiosurgery for Brain Metastases

Abstract

Stereotactic radiosurgery (SRS) is increasingly utilized to treat the resection cavity following resection of brain metastases and recent randomized trials have confirmed postoperative SRS as a standard of care. Postoperative SRS for resected brain metastases improves local control compared to observation, while also preserving neurocognitive function in comparison to whole brain radiation therapy (WBRT). However, even with surgery and SRS, rates of local recurrence at 1 year may be as high as 40%, especially for larger cavities, and there is also a known risk of leptomeningeal disease after surgery. Additional treatment strategies are needed to improve control while maintaining or decreasing the toxicity profile associated with treatment. Preoperative SRS is discussed here as one such approach. Preoperative SRS allows for contouring of an intact metastasis, as opposed to an irregularly shaped surgical cavity in the post-op setting. Delivering SRS prior to surgery may also allow for a “sterilizing” effect, with the potential to increase tumor control by decreasing intra-operative seeding of viable tumor cells beyond the treated cavity, and decreasing risk of leptomeningeal disease. Because there is no need to treat brain surrounding tumor in the preoperative setting, and since the majority of the high dose volume can then be resected at surgery, the rate of symptomatic radiation necrosis may also be reduced with preoperative SRS. In this mini review, we explore the potential benefits and risks of preoperative vs. postoperative SRS for brain metastases as well as the existing literature to date, including published outcomes with preoperative SRS.

Stereotactic radiosurgery in the era of novel systemic therapy for lung cancer brain metastases

“…Some concerns with post-SRS include radiation necrosis and leptomeningeal disease (LMD) recurrence. The hypothesis behind LMD recurrence is the intra-operative seeding of viable tumor cells, which is supported by a study where post-SRS demonstrated higher rates of LMD compared to adjuvant WBRT [15] . A new approach, pre-operative SRS (pre-SRS), is being evaluated as a potential method to decrease radiation necrosis and LMD.…”

“…Potential benefits of pre-SRS include: (1) better local tumor control through improved delineation when contouring an intact metastasis compared to an irregularly-shaped surgical cavity; (2) reduced risk of radiation necrosis, as there is no need to treat surrounding brain tissue and the majority of the treated BM will be resected; (3) reduced risk of LMD as a result of a potential sterilizing effect via the intraoperative seeding of treated tumor cells; and (4) the potential to treat more patients, as with post-SRS some patients are lost to follow-up. A potential disadvantage includes reduced wound healing [15] . Asher et al [16] evaluated pre-SRS in 47 patients, demonstrating its safety and efficacy with local control rates of 85.6% at 12 months.…”

Preoperative Radiosurgery in Management of Brain Metastases

“…With an end goal to positively enhance the adverse outcomes, the The important discoveries of the postoperative cavity SRS studies were the excessive rates of local recurrences (≤44%), radiation necrosis (≤49.4% in 24 months), LMD (≤31%, mostly in 1year of treatment), the considerable potential for higher neurotoxic events due to the necessity for planning target volume (PTV) margins, and target volume definition difficulties caused by the postoperative cavity dynamics [3,[43][44][45][46]. Therefore, taken together, these significant restrictions of the postoperative SRS soundly expanded the enthusiasm for PO-SRS as a theoretically valid alternative, likewise the many other tumor primaries, like rectal cancers.…”

“…However, as recently shown by Prabhu et al only 2 (1.7%) of 120 patients couldn't undergo the planned surgery, because of intercurrent illnesses [54]. On the other hand, contrasted with the typical 6 to 48 hours interval between the PO-SRS and surgery, the frame-based SRS is frequently performed 2 to 5 weeks of surgery leading to a prolonged time frame provision for development of postoperative complications which may defer or cancel the intended postoperative SRS due to numerous causes including the early tumor progression [3].…”

“…For notable instance, the incidence of BM is 20-fold higher than the most common adult brain tumor, namely the glioblastomamultiforme [2]. Regrettably, the incidence of BM typically tends to further increase in the near future due to the implementation of more frequent patient surveillance with dedicated imaging leading to more remarkable rates of detection and allowance of more extended times for BM occurrence in the presence of more effective locoregional and systemic treatments, which significantly enhanced overall survival (OS) times than ever before, particularly the targeted chemotherapies [3]. However, likewise the conventional systemic chemotherapeutics, strikingly contrasting with their excellence in locoregional and systemic tumor control, the potential disadvantage of such targeted agents in common is their inefficiency in penetration of the blood-brain-barrier (BBB) which adds to the increased BM rates.…”