Supralesional Ablation Volumes Are Feasible in the Posterior Fossa and May Provide Enhanced Symptomatic Relief

Abstract

BACKGROUND Laser interstitial thermal therapy (LITT) for posterior fossa lesions remains rare as the small size of the infratentorial compartment, proximity to the brainstem, and thickness/angulation of the occipital bone creates barriers to procedural success. Furthermore, evaluation of the effect of ablation volume on outcomes is limited. OBJECTIVE To analyze our institutional experience with LITT in the posterior fossa stratifying perioperative and long-term outcomes by ablation volumes. METHODS Seventeen patients with posterior fossa lesions treated with LITT from 2013 to 2020 were identified. Local progression-free survival (PFS), overall survival, steroid dependence, and edema reduction were evaluated with Kaplan-Meier analysis grouped by ablation volume. Preoperative, postoperative, and last known Karnofsky Performance Status (KPS) were compared using a matched paired t test. RESULTS No differences in pathology, preoperative KPS, or preoperative lesion volume were found between patients with total (100%-200% increase in pre-LITT lesion volume) versus radical (>200% increase in pre-LITT lesion volume) ablations. Patients who underwent radical ablation had a higher postoperative KPS (93 vs 82, P = .02) and higher KPS (94 vs 87, P = .04) and greater reduction in perilesional edema at last follow-up (P = .01). Median follow-up was 80.8 wk. CONCLUSION Despite obvious anatomical challenges, our results demonstrate that radical ablations are both feasible and safe in the posterior fossa. Furthermore, radical ablations may lead to greater decreases in perilesional edema and improved functional status both immediately after surgery and at last follow-up. Thus, LITT should be considered for patients with otherwise unresectable or radioresistant posterior fossa lesions.

Laser Interstitial Thermal Therapy for Posterior Fossa Lesions: A Systematic Review and Analysis of Multi-Institutional Outcomes

“…One study reported only the diameters of the lesions on posterior fossa and was also excluded in pre-LITT volume’s measurement [ 17 ]. Three studies reported pre- and postprocedural KPS scores, with a combined mean score of 90 pre-LITT and 80 post-LITT for 38 patients [ 12 , 14 , 15 ].…”

“…Morbidity and mortality data could be extracted for 131 of the 150 patients included in this study. Nine deaths (9/131) resulted from disease progression, treatment failure, or metastasis, and no death occurred from LITT treatment [ 11 , 25 ]; 103 patients had no procedural complications and showed stabilization of disease at the time of last follow-up, which ranged from 2 to 24 months [ 11 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 23 , 25 ]; and 19 patients developed intra- or postoperative complications, including transient and permanent neurologic deficits [ 11 , 12 , 14 , 21 , 23 , 25 ]. Procedure-related complications, usually including new neurologic deficits, occurred in approximately 14.5% (19/131) of the pooled sample.…”

“…Luther et al stated that radical ablations are both possible and safe in the posterior fossa. Immediately after surgery and at the time of the final follow-up, radical ablations may result in higher reductions in perilesional edema and an enhanced functional status [ 12 ].…”

“…According to our review, there were 6 records (6/131) of posterior fossa syndrome (PFS), including 2 cases of slurred speech [ 11 ], 1 case of scanning speech [ 11 ], 1 case of speech impairment [ 12 ], 1 case of dysarthria [ 23 ], and 1 case of dysarthria due to a new lesion [ 16 ]. Khan et al reported that 34% of their medulloblastoma patients who received surgical resection had PFS.…”

“…Various techniques, such as OsiriX MD (Pixmeo SARL, Geneva, Switzerland) [ 11 , 12 ] and iplan workstation (BrainLab, Munich, Germany) [ 13 , 14 , 15 ], were used in different studies to provide tumor dimensions and volumetric analyses.…”