Use of Apparent Diffusion Coefficients in Evaluating the Response of Acoustic Neuromas to Gamma Knife Surgery

Do Hoon Kwon1, Jeong Hoon Kim2, Won Hyoung Park3, Do Hee Lee3, Hyun Jung Kim3

1Seoul, Korea, Republic Of 2Asan Medical Center, College of Medicine, Univ. of Ulsan 3Asan Medical Center

Keywords: vestibular schwannoma, magnetic resonance imaging, gamma knife, Imaging, radiosurgery

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     Large cystic metastatic brain tumors can be treated with surgical resection, radiation therapy and stereotactic radiosurgery. However, single treatment modality is not effective to improve the quality of life for patients harboring these tumors. Stereotactic radiosurgery alone is also dangerous when tumor volume is large.
     Therefore, in the management of large cystic metastatic brain tumors, multimodality treatment, cyst aspiration and radiosurgery with the same stereotactic frame is one option.
     The study population consisted of 34 patients( 17 males, 17 females. Mean age, 58 years) with cystic metastatic brain tumors treated from January 2002 to January 2010.
      Most frequent primary focus was lung cancer ( non small cell lung cancer 17, small cell lung cancer 2 ). Stereotactic cyst aspiration and Gamma Knife Radiosurgery were performed with a single frame application on the same day with pre and post operative MR guidance. Preoperative cyst volume was 24.2 cc. Prescribed mean dose to the tumor margin was 20 Gy. After treatment, patients were evaluated by MRI every 2 or 3 months.
     Preoperative tumor volume( mean 24.2cc) decreased about 76% after aspiration( mean 5.6cc ). After radiosurgery, 17 (50%) patients demonstrated tumor control, 8 (23.5%) patients showed local tumor progression and 9 (26.5%) patients showed remote new metastasis, mean follow-up period was 13.1 months. During this periods, 27 patients died. Twenty four patients died from primary cancer progression or unrelated illness and 3 patient died from brain lesion. The overall mean survival after these procedure was 17.8 months in RPA class1, 10.9 months in RPA class 2 and 6.1 months in RPA class 3. There was no procedure related mortality or morbidity at the surgery and GKRS or during follow-up periods.
     This was a retrospective study.
     Cyst aspiration and stereotactic radiosurgery with a same stereotactic frame reduced tumor volume, relieving acute symptoms, increasing tumor control rates, decreasing complications and increasing median survival.
     These results support the usefulness and safety of stereotactic radiosurgery after cyst aspiration. This method is especially effective for the patients whose physical condition is poor for general anesthesia and those with metastatic brain tumors located in eloquent areas.


Project Roles:

D. Kwon (), J. Kim (), W. Park (), D. Lee (), H. Kim ()