Linear accelerator based stereotactic radiosurgery may be a promising therapeutic option for patients presenting with metastatic tumors in critical eloquent parts of the brain, according to a study presented at the 5th International Conference of the Novalis Circle held last month in Munich.
Surbhi Jain, MD, of the H. Lee Moffitt Cancer Center and the University of South Florida in Tampa, Fla., and colleagues retrospectively evaluated the effectiveness of linear accelerator based stereotactic radiosurgery in patients with brain metastases located in the eloquent brain.
The researchers reviewed the cases of 191 patients with 543 brain metastases presenting to the medical center between 2008 and 2009. Of the 543 tumors, 106 tumors were located in the eloquent brain and each patient underwent stereotactic radiosurgery.
Metastatic tumors were located in the primary somatosensory cortex of the brain in 50 patients, the brain stem in 28, speech in 10, basal ganglionic-capusloinsular area in seven, thalamo-ventricular in six and the visual pathways in five.
The average median tumor volume at the time of the treatment was 0.82 cm3, and the average prescribed radiation dose was 21 Gy to the 80 percent isodose line, said the authors, noting that the prescribed radiation dose was based on tumor volume, location in the eloquent brain and a predicted dose-response relationship of brain tissue necrosis.
The researchers selected local tumor control based on radiological response of serial follow-up imaging as the primary endpoint of their study, and the metastatic tumors were followed up with postradiosurgery MR imaging every two to three months after treatment. Due to short-term survival and patients lost to follow-up, imaging follow-up studies were not completed in 22 patients. An imaging follow-up evaluation at an average of 24 weeks was completed in the remaining 84 patients.
Twenty-five tumors disappeared at follow up, while 28 shrank, seven grew larger and 27 remained unchanged. The unchanged or reduced lesions and those that had disappeared were classified as under control by Jain and colleagues. Adverse neuroimaging changes resulting in the worsening of neurological functions occurred in 12 percent of metastatic tumors. Of this group, intratumor hemorrhage occurred in six tumors and radiation induced changes in four tumors.
Overall local tumor control rate was determined to be 95 percent with stereotactic radiosurgery for this patient cohort, and the risks associated with the treatment in an eloquent location were low, the authors wrote.
“We were extremely encouraged to find a non-invasive treatment that can produce a tumor control rate of 95 percent in an extremely sensitive part of the brain, which controls speech, motor function and senses. The data validate frameless radiosurgery as a safe, precise approach to treatment and make a strong case for increased use among clinicians,” concluded Jain.