Research on results and approach/method

[jeremy]

As promised (or threatened, if you like on my other thread in radiosurgery, here are links to studies I've found that talk about results from microsurgery, including some comparisons of the various approaches.

http://archotol.ama-assn.org/cgi/content/extract/129/8/903?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=schwannoma&searchid=1130218856628_1197&stored_search=&FIRSTINDEX=0&journalcode=archotol
Microsurgery vs Gamma Knife Radiosurgery for the Treatment of Vestibular Schwannomas (Aug 2003)
Bottom line: the cranial nerve preservation rates are essentially equal between surgery and gamma knife treatment.  However, tumor recurrence rates are significantly worse after radiation.  This may lead to an overall lower cranial nerve preservation rate.  The risk of radiation induced tumors is also a serious concern.  Elderly patients with small tumors and patients who are otherwise very poor surgical candidates are 2 groups for whom gamma knife radiation might be the preferred treatment.  For most patients, microsurgical resection should remain the treatment of choice
[But, note that they say “these gamma knife data were selected from reports where larger doses of radiation were prescribed than what is currently used�]
[This study also notes “Radiation carcinogenesis is not completely understood, but there seems to be a steep rise in incidence of tumors at low doses, such as those given for gamma knife radiotherapy�, citing Bradley, “radiation-induced tumors of the head and neck�, Curr Opin Otolaryngol Head Nec Surg. 2002; 10:97-103]

http://www.laryngoscope.com/pt/re/laryngoscope/abstract.00005537-200011000-00016.htm;jsessionid=DdPnHIMq8La82u2AH5mB0r5bA9UtKX1lg4G9zCNSqtFd2os0ums0!-352798717!-949856145!9001!-1
A Meta-analysis Comparing Outcomes of Microsurgery and Gamma Knife Radiosurgery
Laryngoscope. 110(11):1850-1856, November 2000.
Kaylie, David M. MD; Horgan, Michael J. MD; Delashaw, Johnny B. MD; McMenomey, Sean O. MD
Objectives/Hypothesis: Surgery has been the most common treatment for acoustic neuromas, but gamma knife radiosurgery has emerged as a safe and efficacious alternative to microsurgery. This meta-analysis compares the outcomes of the two modalities.
Study Design: A retrospective MEDLINE search was used to find all surgical and gamma knife studies published from 1990 to 1998 and strict inclusion criteria were applied.
Results: For tumors less than 4 cm in diameter, there is no difference in hearing preservation (P = .82) or facial nerve outcome (P = .2). Surgery on all sized tumors has a significantly lower complication rate than radiosurgery performed on tumors smaller than 4 cm (P = 3.2 x 10-14). Surgery also has a lower major morbidity rate than gamma knife radiosurgery (P = 2.4 x 10-14). Tumor control was defined as no tumor recurrence or no tumor re-growth. Surgery has superior tumor control when tumors are totally resected (P = 9.02 x 10-11). Assuming that all partially resected tumors will recur, surgery still retains a significant advantage over radiosurgery for tumor control (P = .028).
Conclusion: Data from these studies date back to the late 1960s and do not completely reflect outcomes using current imaging and procedures. A major difficulty encountered in this study is inconsistent data reporting. Future surgical and radiation reports should use standardized outcomes scales to allow valid statistical comparisons. In addition, long-term results from gamma knife radiosurgery using lower dosimetry have not been reported. Surgery should remain the therapy of choice for acoustic neuromas until tumor control rates can be established

http://www.acousticneuroma.neurosurgery.pitt.edu/docsurvey.html
A Survey of Neurosurgeons’ preferences: Radiosurgery, Resection, Fractionated or Observation? (2004)
A survey was mailed to members of the Congress of Neurological Surgeons in July 2002. Six hundred sixty-three surgeons responded to the survey (30%). The survey was mailed with four questions written on one page. Forty one percent of responders were between the ages of 40 and 50. Eighty percent of neurosurgeons surveyed had either performed radiosurgery on a patient with an acoustic neuroma or had referred a patient for neurosurgery (n=530).
Response to scenario #1: The majority of surgeons stated that they would choose stereotactic radiosurgery for management of their small acoustic tumor (n=283; 43%). Only 122 surgeons stated that they would choose surgical resection of their tumor (18%). Fractionated radiotherapy was chosen by 2% of responders. Interestingly, 240 surgeons stated that they would continue to observe their tumor (36%) rather than undergoing any specific treatment at the present time.
Response to scenario #2: In this scenario, the neurosurgeon had a medium size acoustic tumor that indented the middle cerebellar peduncle but without compression of the fourth ventricle. The tumor measured 22 mm in the maximum diameter. The minority of surgeons recommended continued observation for a tumor of this size (6%) (table 2). Surgical resection was recommended by 347 surgeons (52%), whereas radiosurgery was chosen by 261 surgeons (39%). Fractionated radiotherapy was only chosen by 3%.

http://archotol.ama-assn.org/cgi/content/full/129/4/429
Comparison of Facial Nerve Function Results After Translabyrinthine and Retrosigmoid Approach in Medium-Sized Tumors
Objective  To compare postoperative facial nerve function results according to surgical approach.
Study Design  Retrospective case review study.
Setting  All surgical procedures were conducted in collaboration with a neurosurgery team in teaching hospitals with an academic affiliation.
Patients  Patients with medium to large vestibular schwannomas, with the tumor size ranging from 2 to 3 cm. Ninety-eight patients were identified from an "Acoustic Neuroma Database" (date range of search, 1983-2000).
Main Outcome Measures  The House-Brackmann scale was used for grading facial function in the immediate postoperative period and 1 year after. Guidelines of the American Academy of Otolaryngology–Head and Neck Surgery were used for classification of hearing preservation.
Results  Of the 98 patients, 17 were operated on through a retrosigmoid approach and 81 through the translabyrinthine route. The mean ± SD ages of these 2 groups of patients were 46 ± 13 and 51 ± 14 years, respectively; mean ± SD tumor sizes were 2.5 ± 0.27 and 2.6 ± 0.28 cm, respectively. One year after tumor removal via retrosigmoid approach, 10 (59%) of the 17 patients had good (grade I-II) facial functions and 2 (12%) had poor (grade V-VI) function. In the translabyrinthine group, 54 (68%) of 79 patients (2 patients had subtotal total tumor removal) had good facial nerve function at the end of the 1-year follow-up, and 13 (17%) continued to have poor facial function. The difference between these groups was not statistically significant (P>.05). Hearing was preserved in 4 (24%) of the 17 patients in the retrosigmoid group.
Conclusion  Although the translabyrinthine approach may offer better long-term facial function compared with the retrosigmoid approach in patients with medium-sized tumors, the difference between these 2 groups was not significant enough to favor one approach over the other.

http://archotol.ama-assn.org/cgi/content/full/127/5/543
Facial Function in Hearing Preservation Acoustic Neuroma Surgery
Moisés A. Arriaga, MD; Douglas A. Chen, MD
Arch Otolaryngol Head Neck Surg. 2001;127:543-546.
Objective  To determine if facial function is worse after hearing preservation acoustic neuroma surgery (retrosigmoid and middle fossa) than in translabyrinthine surgery.
Design  Retrospective medical record review.
Setting  Private neuro-otology subspecialty practice of patients operated on in a tertiary care hospital.
Patients  This study evaluated 315 consecutive acoustic neuroma surgical procedures between April 1989 and July 1998. A total of 209 translabyrinthine procedures and 106 hearing preservation surgical procedures were performed. The hearing preservation procedures were equally divided between retrosigmoid (n = 48) and middle fossa (n = 58) procedures.
Methods  Medical records were reviewed and tabulated for tumor size, surgical approach, and House-Brackmann facial function grade at short-, intermediate-, and long-term intervals.
Results  Postoperative facial function in hearing preservation surgical procedures at short- and long-term follow-up was not worse than facial function after translabyrinthine surgical procedures in comparably sized tumors.
Conclusion  Concern about postoperative facial function should not be the deciding factor in selecting hearing preservation vs nonhearing preservation acoustic neuroma surgery.

[jeremy]

a few more...


http://www.otology-neurotology.org/ANS/files/2005Abstracts.pdf
American Neurotology Society annual meeting, May 2005, Boca Raton, FL

Small Acoustic Neuromas: Observation Versus Surgical Excision
Ted A. Meyer, MD, PhD, Paul A. Canty, MD Eric P. Wilkinson, MD, Marlan R. Hansen, MD Jay T. Rubinstein, MD, PhD (UW), Bruce J. Gantz, MD
Objective: Evaluate factors affecting outcomes of small acoustic neuroma (AN) removal via a middle cranial fossa (MCF) approach, and compare results to published data on observing AN.
Study design: Retrospective chart review.
Setting: Academic tertiary referral center.
Patients: 160 consecutive patients (ages 19-70) with unilateral AN (0.2-2.5 cm in largest dimension) removed through an MCF approach. 111 patients had preoperative word recognition scores (WRS) => 70%.
Outcome measures: Postoperative WRS. Facial nerve outcomes. Complications.
Hearing Results: Both tumor size and preop WRS were related to postop WRS (p<.01). Patients with tumors <= 1.0 cm (N=91) had a 72% chance of preserving some hearing. If the WRS was also =>70% (N=64), 58% maintained WRS => 70%, and 8 others improved to =>70%. When the tumor was 1.1-1.4 cm (N=34), the chance of preserving some hearing decreased to 41%. If the WRS was also =>70% (N=23), 39% maintained WRS => 70%, and 3 others improved to => 70%. When the tumor reached 1.5-2.5 cm (N=35), the hearing preservation rate was 43%. If the WRS was also => 70% (N=24), only 33% maintained WRS => 70%, and 1 other improved to => 70%.
Facial Function: Good facial nerve function (HB I-II) was achieved in 97% (86% HBI). When tumor size was <= 1.0 cm (N=91), good facial nerve function was obtained in 100% (93% HB I).
Complications: CSF leak - 9 (5.6%), Seizure - 2 (1.2%), Recurrence -1 (0.6%).
Conclusions: Our results suggest that removal of unilateral AN through an MCF approach when the tumor is small and hearing is good may provide the best hearing preservation and facial nerve function. Observation historically results in tumor growth in young and middle-age patients with subsequent hearing loss.

Hearing Preservation in Acoustic Neuroma Surgery: Technique and Results Using the Middle Cranial Fossa Approach
H. Alexander Arts, MD; Steven A. Telian, MD Hussam El-Kashlan, MD; B. Gregory Thompson, MD
Objective: To evaluate surgical results using the middle cranial fossa approach for hearing preservation acoustic neuroma surgery, and to describe modifications to this approach.
Study Design: Retrospective case review.
Setting: Tertiary referral center.
Patients: Sixty-six consecutive patients with acoustic neuroma operated on using our modifications of the middle cranial fossa approach between February 1999 and December 2003.
Interventions: The tumors were removed via the middle cranial fossa approach modified to improve exposure. Standard ABR and facial nerve monitoring were used.
Main outcome measures: Pre and postoperative hearing measures and facial nerve function; tumor size; postoperative complications. Hearing status was categorized into classes A, B, C, and D as described in the American Academy of Otolaryngology “Guidelines for the Evaluation of Hearing Preservation in Acoustic Neuroma,� 1995.
Results: 44 patients had class A hearing preoperatively. Of these, 30 (68%) remained in class A, 2 (5%) deteriorated to class B, and 12 (27%) deteriorated to class D postoperatively. 15 patients had class B hearing preoperatively. Of these, 1 (7%) improved to class A, 9 (66%) remained in class B, 1 (7%) deteriorated to class C, and 3 (20%) deteriorated to class D postoperatively. 1 of 4 patients presenting in class C improved to class B; 2 remained in class C, and one deteriorated to D postoperatively. 3 patients presented in class D and remained so postoperatively. Overall, 44 of 59 (75%) patients with A or B hearing preoperatively maintained A or B postoperatively. Of the 15 patients with class A or B hearing preoperatively and class D hearing postoperatively, 9 had tumors greater than 1.1 cm in greatest dimension. If these patients are excluded, 88% of patients with class A or B hearing preoperatively retained their hearing at A or B levels. At 6 months followup, facial nerve function was (House-Brackmann) grade I in 82%, II in 14%, III in 2%, and IV in 2%. No patients developed grade V or VI weakness. Of the 66 patients, 5 (8%) developed CSF leaks, all of which resolved with lumbar drainage.
Conclusion: With excellent exposure and meticulous surgical technique, hearing was preserved in 75% of cases with tumors less than 1.2cm in greatest dimension. Postoperative facial nerve function was grade I or II in 96%.

Transient Evoked Otoacoustic Emissions Pattern as a Prognostic Indictor for Hearing Preservation in Acoustic Neuroma Surgery
Ana H Kim, MD, Bruce M Edwards, AuD, Steven A. Telian, MD Paul Kileny, PhD, Alexander H Arts, MD
Objective: To determine whether preoperative transient otoacoustic emission (TEOAE) patterns are predictive of successful hearing preservation in acoustic neuroma surgery.
Study Design: Retrospective observational study.
Setting: Tertiary referral medical center
Patients: A convenience sample was identified in whom preoperative TEOAE data were available prior to undergoing acoustic neuroma surgery between 1993 to 2004. Ninety-three patients were identified who met this inclusion criterion.
Interventions: The subjects all underwent middle cranial fossa or retrosigmoid approaches for acoustic neuroma resection. Routine hearing measures were obtained postoperatively.
Main Outcome Measures: Pre and postoperative pure-tone and speech results were categorized into hearing classes A, B, C, and D as described in the American Academy of Otolaryngology guidelines (1995). Hearing preservation was defined by maintenance of the preoperative hearing class or downgrade to within one hearing class. Preoperative TEOAE results were divided into five frequency bands and described as positive if there was a response above the noise floor with > 50% reproducibility.
Results: Hearing was preserved in 51 patients (55%). Of these, 11 (22%) had positive TEOAE response to all five frequency bands tested (1, 1.5, 2, 3, 4 kHz), whereas 40 (78%) had positive TEOAE anywhere from 0 to 4 frequency bands. 42 patients failed to preserve their hearing. Of these, only 3 (7%) had positive TEOAE to all five frequency bands, and 39 (93%) had positive TEOAE anywhere from 0 to 4 out of the five frequency bands (p=0.05). Logistic regression was then used to compare the prognostic value ofTEOAE to other variables associated with hearing preservation such as tumor size, tumor location, preoperative hearing status, and ABR results. In our series, smaller tumor size and prolonged waves on ABR showed the highest significant correlation to hearing preservation (P<0.001).
Conclusions: A robust preoperative TEOAE frequency band pattern may be used as a favorable prognostic indicator to hearing preservation. The prognostic value may be enhanced when combined with other prognostic factors such as tumor size and preoperative ABR results.

http://jnnp.bmjjournals.com/cgi/content/full/75/3/453
Removal of large acoustic neurinomas (vestibular schwannomas) by the retrosigmoid approach with no mortality and minimal morbidity
I Yamakami1, Y Uchino1, E Kobayashi1, A Yamaura1 and N Oka2
Accepted 28 June 2003
Objective: To evaluate the safety and efficacy of removing large acoustic neurinomas ( 3 cm) by the retrosigmoid approach.
Methods: Large acoustic neurinomas (mean (SD), 4.1 (0.6) cm) were removed from 50 consecutive patients by the retrosigmoid suboccipital approach while monitoring the facial nerve using a facial stimulator-monitor. Excision began with the large extrameatal portion of the tumour, followed by removal of the intrameatal tumour, and then removal of the residual tumour in the extrameatal region just outside the porus acusticus. The last pieces of tumour were removed by sharp dissection from the facial nerve bidirectionally, and resected cautiously in a piecemeal fashion.
Results: There were no postoperative deaths. The tumour was removed completely in 43 of 50 patients (86%). The facial nerve was anatomically preserved in 92% of the patients and 84% had excellent facial nerve function (House-Brackmann grade 1/2). One patient recovered useful hearing after tumour removal. Cerebrospinal fluid leak occurred in 4%, but there were no cases of meningitis. All but two patients (96%) had a good functional outcome.
Conclusions: The method resulted in a high rate of functional facial nerve preservation, a low incidence of complications, and good functional outcomes, with no mortality and minimal morbidity. Very favourable results can be obtained using the retrosigmoid approach for the removal of large acoustic neurinomas.

http://www.ajnr.org/cgi/content/abstract/21/8/1540
Serial Follow-up MR Imaging after Gamma Knife Radiosurgery for Vestibular Schwannoma
American Journal of Neuroradiology 21:1540-1546 (8 2000)
Hiroyuki Nakamura,a, Hidefumi Jokuraa, Kou Takahashia, Nagatoshi Bokua, Atsuya Akabanea and Takashi Yoshimotoa
BACKGROUND AND PURPOSE: Gamma knife radiosurgery has become an important treatment option for vestibular schwannoma. The effect of treatment can be assessed only by neuroimaging. We analyzed the evolution of follow-up MR imaging findings after gamma knife radiosurgery to provide information for the clinical management of these tumors.
METHODS: Changes in tumor volume and enhancement were assessed visually on 341 follow-up MR studies obtained in 78 of 86 consecutive patients with unilateral vestibular schwannoma who underwent gamma knife radiosurgery.
RESULTS: Follow-up MR studies were obtained between 10 and 63 months (mean, 34 months) after treatment. Tumor control rate was 81%. Changes in tumor volume were classified as temporary enlargement (41%), no change or sustained regression (34%), alternating enlargement and regression (13%), or continuous enlargement (12%). Temporary enlargement occurred within 2 years after radiosurgery. Changes in tumor enhancement were classified as transient loss of enhancement (84%), continuous increase in enhancement (5%), or no change in enhancement (11%). There was no significant correlation between changes in tumor volume and tumor enhancement. Areas of T2 hyperintensity in adjacent brain tissue appeared in 31% of patients.
CONCLUSION: Dynamic changes in vestibular schwannoma are seen on serial follow-up MR studies obtained after gamma knife radiosurgery. An increase in tumor size up to 2 years after radiosurgery is likely to be followed by regression. Changes in contrast enhancement are not predictive of clinical outcome. Neuroimaging follow-up is recommended

http://www.laryngoscope.com/pt/re/laryngoscope/abstract.00005537-200408000-00026.htm;jsessionid=DdPnHIMq8La82u2AH5mB0r5bA9UtKX1lg4G9zCNSqtFd2os0ums0!-352798717!-949856145!9001!-1   
Retrosigmoid Versus Middle Fossa Surgery for Small Vestibular Schwannomas
Laryngoscope. 114(:1455-1461, August 2004.
Mangham, Charles A. Jr MD
Objectives/Hypothesis: The objective was to determine the effect of approach, middle fossa versus retrosigmoid, on the hearing and facial nerve outcome of surgery for small vestibular schwannomas.
Study Design: The study had two parts, a case study of patient data entered into a prospectively designed database at the author's institution, and a meta-analysis of similar published data.
Methods: There were 73 of the author's private practice patients who met the inclusion criteria of intracanalicular vestibular schwannoma and total tumor removal by a retrosigmoid approach. American Academy of Otolaryngology-Head and Neck Surgery standardized hearing and facial nerve classifications of these patients and similar data from 11 other institutions were used to compare results of the two surgical approaches.
Results: Median facial nerve results for all institutions were significantly better with the retrosigmoid approach (grade I: 95% for retrosigmoid and 81% for middle fossa). Median hearing results trended toward better outcome with the middle fossa approach (same preoperative hearing class: 48% for middle fossa and 39% for retrosigmoid). Individual institution had an equal or greater effect on outcome than the choice of surgical approach.
Conclusion: Surgical team accounted for more variability in hearing and facial nerve outcome than did approach. Retrosigmoid approach yielded significantly better facial nerve outcome. The trend toward better hearing outcome with the middle fossa approach may never achieve statistical significance across institutions because of high variability among surgical teams and small numbers of teams reporting results.

http://www.laryngoscope.com/pt/re/laryngoscope/abstract.00005537-200510000-00022.htm;jsessionid=DdPnHIMq8La82u2AH5mB0r5bA9UtKX1lg4G9zCNSqtFd2os0ums0!-352798717!-949856145!9001!-1
Surgical Salvage after Failed Irradiation for Vestibular Schwannoma
Laryngoscope. 115(10):1827-1832, October 2005.
Friedman, Rick A. MD, PhD; Brackmann, Derald E. MD; Hitselberger, William E. MD; Schwartz, Marc S. MD; Iqbal, Zarina MPH; Berliner, Karen I. PhD
Objectives/Hypothesis: Compare vestibular schwannoma (VS) surgical outcome between patients with prior irradiation and those not previously treated.
Study Design: Retrospective review with matched control group.
Methods: Review of tumor adherence to the facial nerve, facial nerve grade, and complications in 38 patients with radiotherapy as a primary procedure before VS surgical removal and a matched random sample of 38 patients with primary surgery. The majority of the irradiated group had gamma knife radiation therapy. Mean time from irradiation to surgical salvage was 3.3 years (SD = 3.2), with a minimum of 5.2 months and a maximum of 15.8 years. Most (89.5%) patients in each group underwent a translabyrinthine approach. Mean tumor size at surgery was 2.6 cm in each group.
Results: The irradiated group had more moderate to severe adherence of tumor than the controls (89% vs. 63%, P <= .01). They also had a lower rate of good facial function (House-Brackmann grade I/II) (37% vs. 70%) and a higher rate of poor function (grades V or VI) (50% vs. 18%) at follow-up (P <= .019). Results were similar when including only those with good preoperative function (50% vs. 72% and 32% vs. 15%) but did not achieve statistical significance. Surgical time and complications did not differ.
Conclusion: Patients who have undergone irradiation for VS and require surgical salvage may have a more difficult surgery and poorer outcomes than those not previously irradiated. When making their initial choice of treatment, patients should be counseled that surgery might be more difficult after failed stereotactic irradiation

[JHager]

Jeremy,

If you are not a researcher of some sort, you are missing your calling!

Thanks for all the great info, and for all the work putting it together.

Josh