A phase II study presented at the 2024 American Society for Radiation Oncology (ASTRO) Annual Meeting indicates that 177Lu-Dotatate (Lutathera) improves progression-free survival (PFS) in patients with recurrent grade II/III meningioma. The study, led by Dr. Kenneth W. Merrell from the Mayo Clinic Alix School of Medicine, suggests that 177Lu-Dotatate could be a rational therapeutic choice given the limited alternative therapies available for this patient population.
Study Design and Patient Population
The Simon 2-stage designed trial enrolled 20 patients with WHO grade 2/3 meningiomas refractory to surgery and radiation. The median age of patients was 66.8 years, with 35% being female. All patients had previously undergone surgery, with a median of two prior radiotherapy courses. Patients received four cycles of 177Lu-Dotatate at 8-week intervals, following Ga-Dotatate PET/MR imaging.
Efficacy Outcomes
The primary endpoint of the study, PFS, was met with a median PFS of 11.5 months. The 2-year PFS rate was 26.7% (95% CI, 0.12-0.58). The median overall survival (OS) was 27.8 months, with a 1-year OS rate of 88.9% (95% CI, 0.76-1.0) and a 2-year OS rate of 63.8% (95% CI, 0.44-0.92). The best response achieved was stable disease. According to Dr. Merrell, the 6-month PFS rate of 77.8% surpassed the historical benchmark of 26%.
Safety and Tolerability
177Lu-Dotatate was generally well-tolerated in this patient population. Seventy percent of patients received all four infusions. Among those who received four or more cycles, 10% experienced adverse effects (AEs), 10% had other medical problems, and 10% experienced progression. No AEs higher than grade 3 were attributed to 177Lu-Dotatate. The rate of grade 3 non-hematologic AEs was 10%.
Clinical Significance
Meningiomas are the most common type of brain tumor, with a high recurrence risk (40-80%) for WHO grades 2 and 3, leading to a 2 to 3 times higher mortality risk compared to grade 1. At recurrence, these tumors often behave aggressively, and post-surgery and radiation options are limited. Systemic therapy remains off-label with no proven efficacy.
Dr. Merrell noted that somatostatin receptors (SSTR2) are expressed in 80-100% of meningiomas across all grades, making peptide receptor radionuclide therapy a viable option. 177Lu-Dotatate binds with high affinity to SSTR2, allowing for specific and targeted radiation for refractory meningioma.
Expert Commentary
"Considering limited alternative therapies, our results support 177Lu-Dotatate as a rational therapeutic choice," said Dr. Merrell. He concluded that 177Lu-Dotatate demonstrated clinically meaningful outcomes across a broad patient population, marking a significant milestone for refractory meningioma.
Geoffrey B. Johnson, MD, PhD, the co-PI of the trial and a nuclear medicine physician at the Mayo Clinic, added, "With advanced PET imaging, the theranostic approach to treatment helps us to select those patients most likely to benefit from molecularly targeted radiation directly to their tumor cells."
