Integra Foundation Award - Management of Intermediately Sized Brain Metastases of the Primary Motor Gyrus: A Case-Controlled Study

Introduction: Local treatment for dominant or symptomatic brain metastases requires balancing benefits and risks of adding surgical resection to stereotactic radiosurgery/therapy (SRS/SRT). Primary motor cortex (PMC) lesions are perceived to have increased neurologic risks of surgery. Previous literature supporting safe surgical resection of metastatic lesions within the PMC is controversial due to treatment selection bias. Although treatment strategies for large tumors (Surgery+SRS/SRT) and small tumors (SRS/SRT-alone) are generally accepted, optimal management for intermediately sized (1-3cm diameter) tumors is unclear.

Methods: This case-controlled matched study compared neurologic and oncologic outcomes of SRS/SRT-alone versus Surg+SRS/SRT for intermediate-sized PMC metastases. Patients were matched by tumor diameter, primary malignancy radiosensitivity and recursive partitioning analysis (RPA) score. Demographic, tumor characteristics, treatment details, and neurologic outcomes were analyzed.

Results: Among 242 patients with intermediate-sized PMC metastases, 60 (24.8%) underwent Surg+SRS and 182 (75.2%) had SRS/SRT-alone. One-to-one case-controlled matching yielded 30 exact matches. Baseline demographics, preoperative neurological status and preoperative clinical performance status were similar between groups. After treatment, the SRS/SRT-alone patients had a higher frequency of new or persistent motor deficit (80% versus 47%, p=0.007) and lower median overall strength grade (4 [range 3-4] versus 5 [range 4-5], p=0.003) compared to Surg+SRS patients with a mean 14.4±16.0 months follow-up. Conversely, the Surg+SRS group had higher likelihood of improvement in motor function by at least 1 point post-treatment (56% versus 4.8%, p< 0.001) and were more likely to improve to or maintain a post-treatment strength grade 5 (53.3% versus 16.7%, p=0.003) compared to SRS/SRT-alone patients. A decline in motor function by at least 1 point occurred only in SRS/SRT-alone patients (26.7% vs 0%, p=0.009).

Conclusion : In this case-controlled matched analysis, Surg+SRS for intermediate-sized PMC metastases demonstrated greater degree of strength improvement, higher overall motor scores and reduced risk of new neurologic deficits compared to SRS/SRT-alone.