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Complications of Radiosurgery to the Brain
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Complications of Radiosurgery to the Brain
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| The odds and timing to develop a cranial nerve palsy after radiation of an acoustic neuroma based on the maximum dose to the brain stem, from Foote data below using linac based radiosurgery |
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| The odds and timing to develop a cranial nerve palsy after radiation of an acoustic neuroma based on the prescription dose, from Foote data below using linac based radiosurgery |
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| Analysis of risk factors associated with radiosurgery
for vestibular schwannoma. Foote KD, Friedman WA, Buatti JM, Meeks SL, Bova FJ, Kubilis PS. Department of Neurosurgery, University of Florida, Gainesville, USA. J Neurosurg 2001 Sep;95(3):440-9 The aim of this study was to identify factors associated with delayed cranial neuropathy following radiosurgery for vestibular schwannoma (VS or acoustic neuroma) and to determine how such factors may be manipulated to minimize the incidence of radiosurgical complications while maintaining high rates of tumor control. METHODS: From July 1988 to June 1998, 149 cases of VS were treated using linear accelerator radiosurgery at the University of Florida. The overall 2-year actuarial incidences of facial and trigeminal neuropathies were 11.8% and 9.5%, respectively. In 41 patients treated before 1994, the incidences of facial and trigeminal neuropathies were both 29%, but in the 108 patients treated since January 1994, these rates declined to 5% and 2%, respectively. An evaluation of multiple risk factor models showed that maximum radiation dose to the brainstem, treatment era (pre-1994 compared with 1994 or later), and prior surgical resection were all simultaneously informative predictors of cranial neuropathy risk. The radiation dose prescribed to the tumor margin could be substituted for the maximum dose to the brainstem with a small loss in predictive strength. The pons-petrous tumor diameter was an additional statistically significant simultaneous predictor of trigeminal neuropathy risk, whereas the distance from the brainstem to the end of the tumor in the petrous bone was an additional marginally significant simultaneous predictor of facial neuropathy risk. The overall radiological tumor control rate was 93% (59% tumors regressed, 34% remained stable, and 7.5% enlarged), and the 5-year actuarial tumor control rate was 87% (95% confidence interval [CI] 76-98%). Analysis revealed that a radiation dose cutpoint of 10 Gy compared with more than 10 Gy prescribed to the tumor margin yielded the greatest relative difference in tumor growth risk (relative risk 2.4, 95% CI 0.6-9.3), although this difference was not statistically significant (p = 0.207). CONCLUSIONS: Five points must be noted. 1) Radiosurgery is a safe, effective treatment for small VSs. 2) Reduction in the radiation dose has played the most important role in reducing the complications associated with VS radiosurgery. 3) The dose to the brainstem is a more informative predictor of postradiosurgical cranial neuropathy than the length of the nerve that is irradiated. 4) Prior resection increases the risk of late cranial neuropathies after radiosurgery. 5) A prescription dose of 12.5 Gy to the tumor margin resulted in the best combination of maximum tumor control and minimum complications in this series. Analysis of related factors in complications of stereotactic radiosurgery in intracranial tumors. Liu Y, Xiao S, Liu M, Li G, Wang D, He J, Hu B, Zu D. Stereotact Funct Neurosurg 2000;75(2-3):129-32 Department of Radiotherapy, Beijing Hospital, Beijing, China. liuyuanzhao@china.com A retrospective review of 146 patients with intracranial tumors treated with stereotactic radiosurgery was conducted. Sixty-five patients received single-dose treatment and the rest received fractionated stereotactic radiosurgery. Ninety-five patients received conventional radiotherapy in the meantime. RESULTS: Follow-up period was 18-54 months. Follow-up rate was 92.5% and 39 patients (26.7%) had different complications. The Cox statistics showed that target volume, target peripheral dose, target maximal dose, and ratio of maximal dose to peripheral dose are related to the complications. Conversely, neither type of tumor disease, gender, radiation schedule with or without conventional radiotherapy, target minimal dose, nor ratio of target peripheral isodose volume to target volume were found to be related to complications. CONCLUSION: Target volume and dose are the major factors causing complications, and the optimization of the therapeutic planning can play a significant role in reducing them Dose conformity of gamma knife radiosurgery and risk factors for complications. Nakamura JL, Verhey LJ, Smith V, Petti PL, Lamborn KR, Larson DA, Wara WM, McDermott MW, Sneed PK. Department of Radiation Oncology, University of California, San Francisco, CA 94143-0226, USA. Int J Radiat Oncol Biol Phys 2001 Dec 1;51(5):1313-9 PURPOSE: To quantitatively evaluate dose conformity achieved using Gamma Knife radiosurgery, compare results with those reported in the literature, and evaluate risk factors for complications. METHODS AND MATERIALS: All lesions treated at our institution with Gamma Knife radiosurgery from May 1993 (when volume criteria were routinely recorded) through December 1998 were reviewed. Lesions were excluded from analysis for reasons listed below. Conformity index (the ratio of prescription volume to target volume) was calculated for all evaluable lesions and for lesions comparable to those reported in the literature on conformity of linac radiosurgery. Univariate Cox regression models were used to test for associations between treatment parameters and toxicity. RESULTS: Of 1612 targets treated in 874 patients, 274 were excluded, most commonly for unavailability of individual prescription volume data because two or more lesions were included within the same dose matrix (176 lesions), intentional partial coverage for staged treatment of large arteriovenous malformations (AVMs) (33 lesions), and missing target volume data (26 lesions). The median conformity indices were 1.67 for all 1338 evaluable lesions and 1.40-1.43 for lesions comparable to two linac radiosurgery series that reported conformity indices of 1.8 and 2.7, respectively. Among all 651 patients evaluable for complications, there were one Grade 5, eight Grade 4, and 27 Grade 3 complications. Increased risk of toxicity was associated with larger target volume, maximum lesion diameter, prescription volume, or volume of nontarget tissue within the prescription volume. CONCLUSIONS: Gamma Knife radiosurgery achieves much more conformal dose distributions than those reported for conventional linac radiosurgery and somewhat more conformal dose distributions than sophisticated linac radiosurgery techniques. Larger target, nontarget, or prescription volumes are associated with increased risk of toxicity. Dose reduction improves hearing preservation rates after intracanalicular acoustic tumor radiosurgery. Niranjan A, Lunsford LD, Flickinger JC, Maitz A, Kondziolka D. Neurosurgery 1999 Oct;45(4):753-62 Department of Neurological Surgery, University of Pittsburgh, Pennsylvania 15213, USA. OBJECTIVE: To assess the potential for long-term serviceable hearing preservation in intracanalicular acoustic tumor patients who underwent stereotactic radiosurgery. METHODS: Between August 1987 and December 1997, 29 patients with intracanalicular acoustic tumors underwent stereotactic radiosurgery at our center using the Leksell gamma knife (Elekta Instruments, Inc., Atlanta, GA). Fifteen assessable patients had serviceable preradiosurgery hearing (pure tone average, < or = 50 dB; speech discrimination score, > or = 50%). We retrospectively analyzed our hearing results and compared hearing preservation in patients who received a minimal tumor dose of 14 Gy or less versus those who received more than 14 Gy to the tumor margin. RESULTS: No perioperative patient morbidity or mortality was observed. Serviceable hearing was preserved in 11 (73%) of 15 assessable patients (actuarial rate, 65%). Long-term follow-up demonstrated serviceable hearing preservation in 10 (100%) of 10 patients who received marginal tumor doses of 14 Gy or less but in only one of five patients who received more than 14 Gy. Preradiosurgery Gardner-Robertson class was preserved in 49%, and testable hearing was present in 68% of patients who had any testable hearing at presentation. Five patients demonstrated improvement in hearing (three had serviceable and two had nonserviceable hearing before radiosurgery). No patient developed a facial or trigeminal neuropathy. Seven of 13 patients with preoperative tinnitus continued to experience tinnitus in follow-up. Episodic vertigo continued in 3 of the 11 patients who presented with vertigo. CONCLUSION: Gamma knife radiosurgery (using conformal dose planning, small-beam geometry, and < or = 14 Gy to the margin) prevents tumor growth and achieves excellent hearing preservation rates. Reduced-dose radiosurgery for vestibular schwannomas. Petit JH, Hudes RS, Chen TT, Eisenberg HM, Simard JM, Chin LS. Neurosurgery 2001 Dec;49(6):1299-306 Department of Neurological Surgery, University of Maryland Medical Center, Baltimore, Maryland 21201-1595, USA. jpetit001@maryland.edu Between December 1993 and January 2000, 47 patients with vestibular schwannomas were treated at our center with gamma knife radiosurgery. The marginal tumor doses ranged from 7.5 to 14.0 Gy (median, 12.0 Gy) for patients treated after microsurgery and from 10.0 to 15.0 Gy (median, 12.0 Gy) for patients in whom radiosurgery was the primary treatment. The median maximum tumor diameter was 18 mm (range, 3-50 mm). Evaluation included audiometry, neurological examination, and serial imaging tests. A survey was conducted at the time of analysis. RESULTS: Follow-up data were available for 45 patients and ranged from 1 to 7 years (median, 3.6 yr). In 43 patients (96%), tumor control (no radiographic progression or surgical resection) was observed. All 33 previously untreated patients had tumor control. Transient facial weakness, experienced in two patients (4%), had resolved completely within 6 months. No patient developed trigeminal neuropathy. Hearing was diminished from baseline in 12% of patients with useful hearing (Gardner-Robertson Class III). However, all patients with pretreatment hearing Gardner-Robertson Class I or II maintained testable hearing (Class I to III) at the most recent examination. CONCLUSION: Low-dose radiosurgery in this series provided comparable local control and decreased incidences of complications in relation to other reports. Additional follow-up will allow more definitive conclusions to be reached regarding the ultimate rates of tumor control and hearing preservation. Nevertheless, the current dose used for vestibular schwannomas at the University of Maryland Medical Center is 12.0 Gy to the tumor periphery. An integrated logistic formula for prediction of
complications from radiosurgery. Estimation of complications for linear accelerator radiosurgery with
the integrated logistic formula. |
