Lutetium-177 dotatate (177Lu-dotatate; Lutathera) has shown promising activity in patients with surgery- or radiation-refractory grade 2/3 meningioma, according to data from a prospective phase 2 trial presented at the 2024 American Society for Radiation Oncology (ASTRO) Annual Meeting. The study highlights a potential new treatment option for a challenging patient population with limited alternatives.
The trial's findings revealed a median progression-free survival (PFS) of 11.5 months and a 2-year PFS rate of 26.7% (95% CI, 12%-58%). The median overall survival (OS) was 27.8 months. The 1-year OS rate was 88.9% (95% CI, 76%-100%), and at 2 years, it was 63.8% (95% CI, 44%-92%). The best response achieved was stable disease.
Meningioma and the Need for New Therapies
Meningioma is the most common type of brain tumor, with approximately 25,000 new cases diagnosed annually in the United States. World Health Organization (WHO) grades 2 and 3 meningiomas carry a higher risk of recurrence (40% to 80%) and mortality (2 to 3 times higher) compared to grade 1 tumors. Recurrent tumors often exhibit aggressive behavior, and treatment options are limited following surgery and radiation. Systemic therapies are currently used off-label and lack proven efficacy.
The Role of Somatostatin Receptor 2 (SSTR2)
According to Dr. Kenneth W. Merrell, a radiation oncologist at the Mayo Clinic Alix School of Medicine, somatostatin receptor 2 (SSTR2) is expressed in 80% to 100% of meningiomas across all grades. Peptide receptor radionuclide therapy, utilizing peptides linked to radionuclides like 177Lu-dotatate, can bind with high affinity to SSTR2. This allows for targeted radiation of refractory meningiomas with broad applicability.
Trial Design and Patient Characteristics
The Simon 2-stage designed trial enrolled patients with WHO grades 2 and 3 meningioma. Participants underwent gallium dotatate PET/MRI followed by four cycles of 177Lu-dotatate administered at 8-week intervals. Single-photon emission CT/CT dosimetry was performed after the first cycle, between 23 and 168 hours post-infusion. Active monitoring was conducted annually.
The study included 20 patients with a median age of 66.8 years. Thirty-five percent were female, and 55% had an ECOG performance status of 0. Sixty-five percent of patients presented with a neurological deficit, 60% had a seizure history, and 15% were receiving corticosteroids. Ninety-five percent of patients had a WHO grade of 2, and 55% had a Krenning score of 2 or more. All patients had previously undergone surgery, with a median of two prior radiotherapy courses; 15% had prior chemotherapy.
Clinical Outcomes and Safety
The study's clinical outcomes were benchmarked against the Response Assessment in Neuro-Oncology systematic review, which established a 6-month PFS (PFS-6) rate of 26% for WHO grades 2 and 3. Seventy percent of patients received all four infusions of 177Lu-dotatate. Among those receiving four or more cycles, 10% experienced adverse events (AEs), 10% had other medical problems, and 10% experienced disease progression. No AEs higher than grade 3 were attributed to 177Lu-dotatate. The rate of grade 3 nonhematologic AEs was 10%.
Conclusion
Dr. Merrell concluded that 177Lu-dotatate was well-tolerated and demonstrated clinically meaningful outcomes across a broad patient population, marking a significant milestone for refractory meningioma. "Considering limited alternative therapies, our results support 177Lu-dotatate as a rational therapeutic choice," he stated.
