Since getting my AN diagnosis a couple weeks back, I've been spending a lot of time on the radiosurgery vs. microsurgery debate. I saw so many references to the danger and benefits of each approach that I decided to get my hands on as much of the research as I could. I figured I may as well share what I've found. So below are links and abstracts for the studies I've read. Very few of them are available in full text for free, alas, but I've included abstracts and other intersting snippets where possible. There's still enough meat here that it might even be worth spinning up a thread for each one of these studies to discuss issues, but in the interest of time, I'm sticking them all in here for now.  I'll post some additional research on micro-surgery over in that forum.
The main things I took away from all this (your mileage may vary):
- There is no clear concensus on radiosurgery yet. The comments that are published in these journals show some skepticism still about proven efficacy and safety.
- Neurosurgeons tend to have a much worse view of radiosurgery (no surprise there, eh?)
- It's hard to have a good long term study when the protocols keep changing -- very few of these places have used the same protocol for more than 5 years. While in most cases the protocol seems to improve in that they use lower doses, I saw one reference to a study by P. Bradley that potentially lower doses are more likely to cause malignancies, and that it in any case it really takes 10 years to judge the success of radiosurgery
- The meta-analysis by Kaylie towards the end, comparing surgery to radiosurgery results, is an interesting read.
anyhow, here they are:
http://www.otology-neurotology.org/ANS/files/2005Abstracts.pdfAmerican Neurotology Society annual meeting, May 2005, Boca Raton, FL
A Comparison of Growth Patterns of Acoustic Neuromas With and Without Radiosurgery
Alex S. Battaglia, MD, PhD; Bill Mastrodimas, MD; Fred DiTirro, MD; Roberto Cueva, MD
Objective: To compare the natural history of acoustic neuroma growth to the reported growth rate of acoustic neuromas after radiosurgical therapy.
Study Design: Retrospective review.
Setting: Tertiary referral center for 3 million patients.
Patients: 104 patients with an average age of 68 who chose to have their acoustic neuromas managed conservatively with at least 1 year follow-up.
Intervention: Patients underwent serial magnetic resonance imaging for assessment of tumor growth for an average period of 38 months.
Main outcome measure: Growth patterns of untreated and radiosurgically treated acoustic neuromas.
Results: The average growth rate of the untreated tumors was 0.4 mm/yr. 72% grew less than 1mm/yr while 23% grew equal to or more than 1 mm/yr. 10% grew more than 2mm/yr. with growth being noted an average of 2 years after diagnosis. This represents a 90% “control� rate if tumor control rate is defined as less than 2mm growth/yr. Tumor regression occurred in 5% of patients with an average negative growth of -0.74 mm/yr. Tumor control rates range in the radiosurgical literature from 88% to 100%. Average follow-up periods in the radiosurgical literature are generally less than or equal to 3 yrs. Tumor control is not uniformly defined.
Conclusions: It is difficult to establish a significant difference between growth patterns of untreated acoustic neuromas and those treated radiosurgically. In order to establish a significant difference, there need to be well-established criteria for reporting tumor sizes and tumor control rates, and there needs to be longer term follow-up with larger sample sizes.
Distortion of Magnetic Resonance Images Used in Gamma Knife Radiosurgery Treatment Planning: Implications for Acoustic Neuroma Outcomes
David M. Poetker, MD, Paul A. Jursinic, PhD Christina L. Runge-Samuelson, PhD P. Ashley Wackym, MD
Objective: To quantify the image distortion of our series of acoustic neuromas (AN) treated with gamma knife (GK) radiosurgery.
Study Design: Retrospective chart and digital radiographic file review.
Setting: Tertiary referral center.
Patients: Patients undergoing GK for the treatment of AN.
Intervention: Gamma knife radiosurgery.
Main Outcome measure: MR images containing GK treatment plans were reviewed at each axial, sagittal, and coronal slice. The length of the greatest displacement of the treatment plan was measured and the volume of the treatment plan that fell outside of the internal auditory canal (IAC) calculated. Known clinical measurements of audiometric,
vestibular, facial, and trigeminal nerve functions were then compared with current measurements of tumor size.
Results: Twenty-two of the 23 patients had measurable image shifts on the axial images. The range of the image shift was 0 to 5.8 mm, with a mean shift of 1.92 mm (SD±1.29 mm). Tumor volumes of the treatment plan that fell outside of the IAC ranged from 0 to 414 mm3, mean 90.5 mm3. The mean percentage of that fell outside of the IAC was 16.7% of total tumor volume (range 2.4% to 77.6%). We could not draw any consistent correlations between degree of image shift and tumor growth, or objective examination values.
Discussion: We have demonstrated a small, but potentially significant shift in the treatment plan of GK radiosurgery when based on MR images. Although the image shift does not seem to affect the growth of the AN, auditory or facial nerve function, longer-term follow-up is required to fully appreciate the true impact this image shift.
http://www.neurosurgery.pitt.edu/imageguided/papers/acoustic.htmlLong-Term Outcomes After Radiosurgery for Acoustic Neuromas
Douglas Kondziolka, MD, MSc, FRCS(C), L. Dade Lunsford, MD, Mark R. McLaughlin, MD, John C. Flickinger, MD (University of Pittsburgh)
Published in The New England Journal of Medicine 339(20): 1426-1433, 1998
To define outcomes after acoustic tumor radiosurgery, we studied all patients who had radiosurgery at a single center between 1987 and 1992. Five to ten year outcomes were determined through the use of serial imaging studies, physician-based evaluations, and a patient survey.
Results: The clinical tumor control rate (no resection required) was 98%. One hundred tumors (61.7%) were smaller, 53 remained unchanged in size (32.7%) and 9 were slightly larger (5.6%). Resection was performed in 4 patients (2.4%), all within four years. Normal facial function was preserved in 77% of patients (House-Brackmann Grade I) and normal trigeminal function in 73%. Fifty-one percent of patients had no change in hearing grade. No delayed neurologic deficits occurred beyond 28 months following radiosurgery. An outcomes survey was returned by 115 patients (77% of those still living). Fifty-four patients (47%) were employed at the time of radiosurgery and 37 (69%) remained so. Radiosurgery was believed "successful" by 30 of 30 patients who had undergone prior surgery and by 81 (96%) of those who had not had prior resection. At least one complication was described by 36 patients (31%), 56% of which resolved.
Conclusions: Five to ten years after radiosurgery, 97% of surveyed patients believed that radiosurgery provided a satisfactory outcome for their acoustic tumor. Overall, 98% of patients required no other tumor surgery. Morbidity in this early experience was usually transitory, and relatively mild. Radiosurgery provided long-term tumor control associated with high rates of neurologic function preservation and patient satisfaction.
Tumor control and imaging response after radiosurgery
The majority of irradiated acoustic tumors decreased in size over time. At the one year evaluation, the percent of tumors that were unchanged, decreased, or increased was 73.9%, 25.5%, and 0.7% respectively. At year 2 (48.4%, 46.9%, 4.7%) and year 3 (38.1%, 58.8%, and 3.1%), the proportion of patients with smaller tumors had increased substantially. During years one to three the proportion of patients with an increased tumor volume also was higher. This represented either true neoplastic tumor growth (n=4) or tumor death with an expansion of the tumor margins as the central portion of the tumor became necrotic. In the latter patients (n=5) subsequent imaging studies confirmed tumor volume regression. By the third year after radiosurgery, serial imaging studies had identified four patients with progressive tumor growth. These patients underwent resection. Resection of these tumors was described by the operating surgeon as no different from a non-irradiated tumor in three patients, and more difficult in one patient. Facial nerve function deteriorated in three patients.
No further increase in tumor volume was identified in any patient from years 4 to 10 after radiosurgery.
Long-term expectations after radiosurgery
Although longer-term results past 10 years will be necessary to substantiate the potentially curative effects of radiosurgery, we believe that the present analysis makes clear several points. First, radiosurgery is a well-tolerated surgical procedure for patients with acoustic tumors that meets most patients expectations. Second, the rate of tumor volume reduction is significant, and higher than previously believed. Early reports noted a 30-40% rate of tumor regression 10, whereas 72% of patients in this study imaged five or more years past radiosurgery had smaller tumors. With extended follow-up most patients have tumors that are regressed in size, not just merely unchanged. Third, when tumor growth does occur, it does so early after radiosurgery. Fourth, post-radiosurgery cranial neuropathy or other neurologic symptoms occur within the first three years, are usually transient, and are relatively mild. Fifth, older patients with larger (2 to 3 cm) tumors remain with a small risk (3%) for the development of hydrocephalus. This risk is similar to that observed with conservative management or after surgery.(2,7) Finally, over the long-term, the vast majority of patients describe radiosurgery as a successful treatment for their acoustic tumor and would recommend it to friends or family. Understanding the foundations of patient decision making is important as we determine methods to analyze results and make therapeutic recommendations.
http://www.neurosurgery.pitt.edu/imageguided/papers/abstracts/acoustic5y.htmlResults of Acoustic Neuroma Radiosurgery: An Analysis of Five Years' Experience Using Current Methods
John C. Flickinger, M.D., Douglas Kondziolka, M.D., M.Sc., FRCS(C), Ajay S. Niranjan, M.S. M.Ch., L. Dade Lunsford, M.D.
Published in Journal of Neurosurgery 94:1-6, 2001
Object: The goal of this study was to define tumor control and complications of radiosurgery encountered using current treatment methods for the initial management of patients with unilateral acoustic neuromas.
Methods: One hundred ninety patients with previously untreated unilateral acoustic neuromas (vestibular schwannomas) underwent gamma knife radiosurgery between 1992 and 1997. The median follow-up period of these patients was 30 months (maximum 85 months). The marginal radiation doses were 11 to 18 Gy (median 13 Gy), the maximum doses were 22 to 36 Gy (median 26 Gy), and the treatment volumes were 0.1 to 33 cm3 (median 2.7 cm3)
The actual 5-year clinical tumor-control rate (no requirement for surgical intervention) for the entire series was 97.1 ± 1.9%. Five-year actuarial rates for any new facial weakness, facial numbness, hearing-level preservation, and preservation of testable speech discrimination were 1.1 ± O.8%, 2.6 ± 1.2%, 71 ± 4.7%, and 91 ± 2.6%, respectively. Facial weakness did not develop in any patient who received a marginal dose of less than 15 Gy (163 patients). Hearing levels improved in 10 (7%) of 141 patients who exhibited decreased hearing (Gardner-Robertson Classes II-V) before undergoing radiosurgery. According to multivariate analysis, increasing marginal dose correlated with increased development of facial weakness (p = 0.034g) and decreased preservation of testable speech discrimination (p = 0.0122)
Conclusion: Radiosurgery for acoustic neuroma performed using current procedures is associated with a continued high rate of tumor control and lower rates of posttreatment morbidity than those published in earlier reports.
http://jnnp.bmjjournals.com/cgi/content/full/74/11/1536Gamma knife stereotactic radiosurgery for unilateral acoustic neuromas
J G Rowe, M W R Radatz, L Walton, A Hampshire, S Seaman and A A Kemeny
Department of Stereotactic Radiosurgery, Royal Hallamshire Hospital, Sheffield, UK
Accepted 15 February 2002
Objective:To evaluate the clinical results achievable using current techniques of gamma knife stereotactic radiosurgery to treat sporadic unilateral acoustic neuromas
Results:A tumour control rate in excess of 92% was achieved, with only 3% of patients undergoing surgery after radiosurgery. Results were less good for larger tumours, but control rates of 75% were achieved for 35–45 mm diameter lesions. Of patients with discernible hearing, Gardner-Robertson grades were unchanged in 75%. Facial nerve function was adversely affected in 4.5%, but fewer than 1% of patients had persistent weakness. Trigeminal symptoms improved in 3%, but developed in 5% of patients, being persistent in less than 1.5%. Transient non-specific vestibulo-cochlear symptoms were reported by 13% of patients.
Conclusions:Tumour control rates, while difficult to define, are comparable after radiosurgery with those experienced after surgery. The complications and morbidity after radiosurgery are far less frequent than those encountered after surgery. This, combined with its minimally invasive nature, may make radiosurgery increasingly the treatment of choice for small and medium sized acoustic neuromas.
a 2004 paper on GK success – 38 patients studied, but only 7 were still in this study 3 years later
http://www.mcw.edu/display/displayFile.asp?docid=6991&filename=/User/amonroe/ResearchGKAcousticNeuroma2004.pdfGamma Knife Radiosurgery for Acoustic Neuromas Performed by a Neurotologist: Early experiences and outcomes
Medical college of Wisconsin, 2004
Objective: to asses early outcomes after Gamma knife radiosurgery of acoustic neuromas and other skull base tumors
Resultss: from june 2000 until March 2004, 38 patients were treated, and these included 33 acoustice neruomas, two meningiomas, one glomus jugulare tumor, and two facial neuromas. Greater than 36 monh follow-up was available in 7 patients, > 24 months in 24, <12 monthis in 31, and > 6 months in 34 patients. Statistically significant reduction in tumor size was seen over time, and tumor control was achieved in all but two patients. Various patterns of changes in auditory function, both in threshold and speech discrimination were observed in either positive or negative directions.
Conclusions: Preliminary experience with Gamma knife radio-surgery indicates that this treatment method represents another option for neruo-otologists to use in managing patients with skull base tumors
