Magnetic Resonance Imaging-Guided Laser Interstitial Therapy for In-Field Recurrence After Stereotactic Radiosurgery: Is Complete Ablation Required for Local Control?

Background: Magnetic resonance imaging-guided laser interstitial therapy (MrLITT) presents a new valuable treatment alternative when the in-field recurrence (IFR) of metastatic brain tumors is difficult to safely access with open surgery or maximum radiation therapy has already been completed.

Objective: To examine the effects of MrLITT on longevity outcomes based on volume of ablation.

Methods: A retrospective study was carried out of 35 patients treated with MrLITT for IFR after radiosurgery for metastatic brain tumors at a single institution from 2010 to 2016. Overall survival (OS) and progression-free survival (PFS) were analyzed with Kaplan-Meier and Cox regression analyses according to ablation volume. Univariate and multivariate analyses further assessed risk factors based on ablation volume.

Results: Kaplan-Meier analyses showed no significant differences between total and subtotal ablation groups in OS (61.1 vs. 49.7 weeks) and PFS (45.1 and 42.7 weeks), respectively (P > 0.05). In the subtotal ablation group, independent risk factors included preoperative tumor volume (hazard ratio [HR], 1.24; P = 0.05) for OS and residual tumor volume (HR, 2.62; P = 0.01) for PFS. Multivariate Cox regressions suggested no significant differences in OS (HR, 1.03; P = 0.19) and PFS (HR, 1.02; P = 0.24) between total and subtotal ablation groups, whereas preoperative tumor volume remained a risk factor for decreased OS (HR, 1.23; P = 0.004).

Conclusions: MrLITT is an effective treatment option for IFR after radiosurgery for metastatic brain tumors. The benefits of more aggressive gross total ablations of deep targets near eloquent cortices are limited compared with effective subtotal ablations, but the amount of residual tumor volume left must be appropriately balanced.