A promising new approach combining laser therapy with immunotherapy is showing significant improvements in survival rates for patients battling recurrent high-grade astrocytoma (rHGA), an aggressive and often fatal form of brain cancer. The treatment, detailed in a Phase 1/randomized Phase 2b clinical trial published in Nature, offers a potential lifeline for individuals with limited treatment options.
rHGA, a cancer that returns after initial treatment, has historically proven resistant to immune checkpoint inhibitors (ICIs), a class of drugs that boost the body’s natural defenses against cancer. This new strategy, however, appears to overcome that resistance by first using laser interstitial thermal therapy (LITT) to directly target and destroy tumor cells, potentially priming the immune system to respond more effectively to subsequent immunotherapy. The combination therapy—LITT followed by the immunotherapy drug pembrolizumab—demonstrated a substantial benefit compared to a control group receiving surgery followed by pembrolizumab.
The trial involved 39 patients who underwent treatment according to protocol. Researchers found that the median overall survival for patients receiving LITT plus pembrolizumab was 11.8 months, compared to just 5.2 months for those who received non-LITT surgery followed by pembrolizumab. Perhaps even more striking, 42% of patients in the LITT plus pembrolizumab group were still alive at 18 months, compared to none in the control group. The hazard ratio for overall survival favored the LITT combination at 0.17 (95% confidence interval, 0.06–0.49. P=0.0002), indicating a significant reduction in the risk of death. Progression-free survival was also significantly longer in the LITT plus pembrolizumab group (4.5 months versus 1.6 months; hazard ratio 0.21; 95% CI, 0.08–0.56; P=0.0006). These findings suggest a meaningful clinical benefit for patients with this devastating diagnosis.
How the Two-Part Therapy Works
LITT is a minimally invasive procedure that uses focused laser energy to heat and destroy cancerous tissue within the brain. It allows surgeons to target tumors with precision, minimizing damage to surrounding healthy brain tissue. Following LITT, patients received pembrolizumab, an anti-PD-1 immunotherapy drug. Pembrolizumab works by blocking the PD-1 protein on immune cells, allowing them to recognize and attack cancer cells more effectively. The researchers hypothesized that LITT would release tumor antigens, essentially signaling the immune system to recognize the cancer as a threat, thereby enhancing the effectiveness of pembrolizumab. The trial results appear to validate this hypothesis.
Trial Design and Early Results Prompted a Shift
The initial Phase 2b study was designed to randomize up to 45 patients in a 1:1 ratio to either LITT plus pembrolizumab or non-LITT surgery plus pembrolizumab. However, after reviewing accumulating efficacy data from the first 21 patients, an independent Data and Safety Monitoring Committee recommended halting randomization. The committee observed limited benefit from the non-LITT surgery plus pembrolizumab arm, leading researchers to enroll the remaining 24 patients in the LITT plus pembrolizumab group. This adaptive design allowed the trial to focus on the treatment arm demonstrating the most promise.
Safety and Tolerability
Importantly, the combination therapy was well-tolerated by patients. The Phase 1 dose-escalation lead-in study, involving nine patients, revealed no dose-limiting toxicities, leading to the selection of 200mg of pembrolizumab every three weeks as the recommended Phase 2 dose. Whereas further research is needed to fully assess long-term safety, the initial findings suggest that this treatment approach is reasonably safe for patients with rHGA. Medical Xpress reports that treatment was well tolerated.
What So for Brain Cancer Patients
The results of this trial represent a significant step forward in the treatment of recurrent high-grade astrocytoma. While not a cure, the combination of LITT and pembrolizumab offers a substantial improvement in survival compared to current standard-of-care treatments. The findings suggest that a targeted, localized approach like LITT can effectively prime the immune system, making it more receptive to immunotherapy. This strategy could potentially be applied to other types of brain tumors as well. Researchers are continuing to investigate the mechanisms underlying this response and explore ways to further optimize the treatment regimen.
The study’s authors note that further research is needed to confirm these findings in larger, multi-center trials. They are also investigating biomarkers that could support identify patients who are most likely to benefit from this combination therapy. The ultimate goal is to develop personalized treatment strategies that maximize the chances of survival for individuals with this challenging disease.
The next steps involve continued follow-up of patients enrolled in the trial and the initiation of larger, confirmatory studies. Researchers are also exploring the potential of combining LITT and pembrolizumab with other immunotherapies or targeted therapies to further enhance treatment efficacy. Patients and caregivers seeking more information about clinical trials and treatment options for rHGA are encouraged to consult with their healthcare providers and visit the National Institutes of Health’s ClinicalTrials.gov website.
If you or someone you know is affected by brain cancer, resources are available. The National Brain Tumor Society (https://braintumor.org/) provides information, support and advocacy for patients and families. The American Cancer Society (https://www.cancer.org/) also offers comprehensive resources and support services.
Do you have thoughts on this promising new treatment? Share your comments below.
Related reading
