Leuthardt, Eric C.

Abstract Immune checkpoint inhibitors (ICIs) have limited benefit in recurrent high-grade astrocytoma (rHGA), largely because the blood–brain barrier and a profoundly immunosuppressive tumor microenvironment prevent T cells from infiltrating. Laser interstitial thermal therapy (LITT) is a minimally invasive, cytoreductive procedure that can “heat up” these otherwise “cold” tumors and sensitize them to ICIs. In this tri-institutional Phase 1/randomized Phase 2 trial (NCT02311582), bevacizumab- and immunotherapy-naïve rHGA patients were initially randomized 1:1 to either LITT followed by pembrolizumab (LITT+PEM) or non-LITT surgery (biopsy or resection) followed by pembrolizumab (NLS+PEM). Phase 2 participants enrolled at a second recurrence—with several already at a third recurrence—underscoring the advanced disease stage of this cohort. After 21 patients, randomization was halted when contemporaneous evidence showed limited benefit from adjuvant ICIs alone, and the remaining 24 patients received only LITT+PEM. In the 21-patient intent-to-treat cohort, LITT+PEM extended median OS to 21.3 months with 54% alive at 18 months (OS18) versus 6.7 months with 12.5% OS18 with NLS+PEM (HR 0.29; 95% CI, 0.01–0.88; p=0.021). Median PFS was 7.8 versus 2.2 months (HR 0.3; 95% CI, 0.10–0.87; p=0.020). Among 39 per-protocol patients, LITT+PEM yielded a median OS of 11.8 months with 42% OS18 versus 5.2 months with 0% OS18 for NLS+PEM (HR 0.17; 95% CI, 0.06–0.49; p=0.0002), and a median PFS of 4.5 versus 1.6 months (HR 0.21; 95% CI, 0.08–0.56; p=0.0006). The combination was well tolerated. Immune profiling revealed that LITT triggers early activation of non-classical monocytes—a change associated with improved survival—while subsequent pembrolizumab unleashes robust CD8⁺ T cell proliferation and clonal expansion. Long-term LITT+PEM survivors developed coordinated memory T-cell responses, whereas shorter-surviving patients exhibited stagnant memory pools and exhausted phenotypes. Together, these results demonstrate that LITT plus pembrolizumab is safe, overcomes rHGA’s immunosuppressive barrier, and mobilizes robust anti-tumor immunity.

Abstract Treatment options for glioblastoma remain limited, particularly for those who are not eligible for traditional resection, whether due to lesion location or inability to tolerate open craniotomy. Maximal-safe resection followed by radiation with concurrent and adjuvant temozolomide offers the best outcomes for patients. Unfortunately, not all tumors are amenable to conventional surgical resection at the time of diagnosis with only about 1/3 of patients able to receive a gross-total resection and 15-25% of patients receiving biopsy only, thus reducing their projected overall survival to 9 months. Laser interstitial thermal therapy (LITT) is a minimally invasive, cytoreductive tool, that has demonstrated safety as a surgical approach to treat primary brain tumors. METHODS Data from LAANTERN prospective multicenter registry (NCT02392078) was analyzed to determine clinical outcomes for patients with new and recurrent IDH wild-type glioblastoma (N=89). Demographics, intraprocedural data, adverse events, KPS, health-economics, and survival data were prospectively collected then analyzed separately for newly diagnosed GBM (N=29) and recurrent GBM (N=60). RESULTS Median overall-survival was 9.73 months (95% CI: 5.16, 15.91) for newly diagnosed patients and median post-procedure survival was 8.97 (6.94, 12.36) months for recurrent patients. Median overall-survival for newly diagnosed patients receiving post-LITT chemoradiotherapy was 16.14 months (6.11, not reached). The median length of hospital stay was 50 hours and 80% of patients were discharged to home. CONCLUSIONS LITT offers an effective cytoreductive approach for patients with newly diagnosed and recurrent IDH wild-type glioblastoma. Importantly, its use in newly diagnosed patients who receive post-LITT chemoradiotherapy leads to a median OS similar to that of patients treated with conventional surgical resection. LITT remains an important alternative for patients with inoperable tumors or those not amenable to resection. Enrollment in LAANTERN is ongoing and these cohorts will be revisited as data continues to mature. Benefits beyond cytoreduction are also being actively explored.

Abstract Background Treatment options for unresectable new and recurrent glioblastoma remain limited. Laser ablation has demonstrated safety as a surgical approach to treating primary brain tumors. The LAANTERN prospective multicenter registry (NCT02392078) data were analyzed to determine clinical outcomes for patients with new and recurrent IDH wild-type glioblastoma. Methods Demographics, intraprocedural data, adverse events, KPS, health economics, and survival data were prospectively collected and then analyzed on IDH wild-type newly diagnosed and recurrent glioblastoma patients who were treated with laser ablation at 14 US centers between January 2016 and May 2019. Data were monitored for accuracy. Statistical analysis included individual variable summaries, multivariable differences in survival, and median survival numbers. Results A total of 29 new and 60 recurrent IDH wild-type WHO grade 4 glioblastoma patients were treated. Positive MGMT promoter methylation status was present in 5/29 of new and 23/60 of recurrent patients. Median physician-estimated extent of ablation was 91%-99%. Median overall survival (OS) was 9.73 months (95% confidence interval: 5.16, 15.91) for newly diagnosed patients and median post-procedure survival was 8.97 months (6.94, 12.36) for recurrent patients. Median OS for newly diagnosed patients receiving post-LITT chemo/radiation was 16.14 months (6.11, not reached). Factors associated with improved survival were MGMT promoter methylation, adjuvant chemotherapy within 12 weeks, and tumor volume <3 cc. Conclusions Laser ablation is a viable option for patients with new and recurrent glioblastoma. Median OS for IDH wild-type newly diagnosed glioblastoma is comparable to outcomes observed in other tumor resection studies when those patients undergo radiation and chemotherapy following LITT.