San Antonio, October 20, 2015—Patients with intermediate meningiomas treated with radiation therapy (RT) after surgery experienced a 96 percent three-year progression-free survival rate and had minimal adverse events, according to research presented today at the American Society for Radiation Oncology's (ASTRO's) 57th Annual Meeting.

Meningioma, the most common type of central nervous system tumor, nearly always forms on the meninges—the membranes that surround the brain and spinal cord. Most meningiomas, approximately 75 percent, are benign (noncancerous), and may not require immediate treatment. However, many need to be removed because of proximity to or impingement of critical structures, tumor growth, or because they are not benign (in other words, they are atypical or anaplastic). Treatment decisions for patients with meningioma depend on many factors, with the more advanced meningiomas often requiring a combination of surgery and RT.

RTOG 0539, the first successfully completed cooperative group meningioma trial, enrolled 244 patients from sites throughout the U.S. and Canada. The study's aim was to estimate patients' three-year progression-free survival (PFS) rates in each of the study's assigned patient groups. PFS indicates the length of time during and after the treatment of a disease that a patient lives with the disease but it does not get worse. The pathology and imaging reports of patients in the trial were all centrally reviewed and patients were assigned to three different groups depending on prognosis and management strategies, which were based upon tumor grade, recurrence status of the tumors and the extent of the surgical removal.
In this first analysis of RTOG 0539, researcherslooked at the three-year PFS and adverse events for the intermediate-risk group of patients (defined as Group 2). Patients in Group 2 had either a newly diagnosed grade II meningioma (atypical, meaning neither frankly malignant nor benign), with gross total resection (GTR, Simpson I-III), or a recurrent grade I (benign) meningioma, meaning that it had been previously treated with surgery but had subsequently progressed. Any degree of surgical resection was permitted for patients with a recurrent grade I tumor. The phase II study compared the patients to a predefined historical control group of intermediate-risk meningiomas.

Of the 56 original patients classified to Group 2, 52 patients received protocol treatment (three were ineligible and one did not receive RT). Of these 52 patients, 36 (69.2 percent) were classified as having WHO grade II tumors with GTR; while 16 patients (30.8 percent) had recurrent grade I tumors. The patients received RT of 54 Gy in 30 fractions post-surgically. While 3-D CRT was permitted within the study guidelines, the majority of patients (84.6 percent) received intensity-modulated radiation therapy (IMRT). This was the first RTOG brain trial with protocol-specific IMRT parameters. Four of the 52 patients withdrew (without recurrence), so 48 patients were evaluable for the primary endpoint of three-year PFS.

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