Abstract
Objectives
The use of radiation therapy has largely widespread and becomes in many centers the preference modality of treatment for symptomatic patients who are old, medically unfit for surgical therapy, those who refuse surgery and in some recurrent or residual growing tumors.
The risk of radiotherapy failure in the treatment of vestibular schwannoma might be underestimated in the literature. The purpose of this study is to show the Gruppo Otologico experience with salvage surgery to better understand the surgical outcomes and difficulties in treating vestibular schwannoma after failed radiotherapy.
Study design
Retrospective chart review of patients who required salvage surgery of vestibular schwannoma after failed radiotherapy.
Settings
Quaternary referral otology and skull base center.
Results
Between 1987 and 2010, 2500 cases of VS underwent surgical treatment at the Gruppo Otologico. Nineteen patients had received stereotactic radiation therapy before the surgical treatment. The interval time between radiotherapy and surgical salvage ranged from 1 to 10 years.
In all the cases decision of surgery was taken following an increase in tumor size with or without new onset of symptoms. Complete tumor removal was achieved in 86.6% of the cases through a transotic, transcochlear or enlarged translabyrinthine approach with trans-apical extension.
Difficult dissection of the tumor was encountered in 93.3% the cases. The facial nerve was anatomically preserved in 93.3% but its function was worsened in 73.3% of patients after at least 6 months of follow up. Malignant transformation of the vestibular schwannoma was encountered in one patient.
Conclusion
Complete surgical resection of VS is more difficult after radiotherapy with relatively poor facial nerve outcomes and nearly impossible hearing preservation.
Patients who receive radiation therapy for the treatment of vestibular schwannoma should be made aware of its potential complications and risk of failure, especially in young patients and NF2 cases.
1
Introduction
Vestibular schwannoma (VS) is a tumor that arises from schwann cells of the vestibular nerve. The incidence ranges from 10 to 20 per million/year and it accounts for 75% of cerebellopontine angle tumors, 10% of intracranial tumors, and 5% of such tumors occur in patients with neurofibromatosis type 2 (NF2) .
The cornerstone treatment is complete surgical resection that requires an experienced surgical team. With the advances in microsurgical techniques and intraoperative monitoring tools, excellent outcomes have been achieved in terms of preservation of the facial nerve (FN) and whenever possible serviceable hearing.
In 1969 Leksell introduced the use of stereotactic radiation therapy for VS treatment . Since then the use of radiation therapy became largely widespread because it seems less invasive than surgery. In many centers it becomes the modality of treatment for symptomatic elderly patients, medically unfit for surgical therapy, patients who refuse surgery, tumors occurring in the only hearing ear and in some recurrent or residual growing tumors.
The main disadvantage of radiation therapy is the non-removal of the tumor that retains the risk of growth and thus requiring long term follow up.
In this paper we present the Gruppo Otologico experience with VS salvage surgery in patients who failed radiation therapy. A literature review and an analysis of the previous reported series were also performed.
2
Materials and methods
Between April 1983 and December 2010, two thousand three hundred eighty vestibular schwannoma were resected by the senior author (M.S.). After departmental and institutional review board approval, a retrospective chart review was conducted on all cases of VS surgically treated after having received radiation therapy at other centers.
Surgical resection following radiotherapy was performed in nineteen patients. Four patients were excluded from this study because they had previous surgery before radiation therapy. Fifteen patients were included; 6 males and 9 females.
The mean age at surgery was 52 ± 14.8 years [20–77 years]. Two patients had NF 2.
The most common symptoms before surgery were dizziness (60%), worsening of hearing loss (53.3%), facial nerve paralysis (26.6%) and facial numbness (13.3%). One patient presented with intracranial hypertension 1 year following radiotherapy; a VP shunt was inserted and the resection of the tumor was performed 3 weeks later ( Table 1 ).
| Patient | Age\Sex | Side | Size | Hearing Pre | New symptoms | FNG pre\post | Interval time between Rx and surgery | Approach | Total Resection | Plane of cleavage | Excessive Tumor adherence to | Complications and notes | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| FN | BS | Ce | Vth | ||||||||||||
| Solitary VS | 59\F | R | 3.4 cm | Dead ear | FP, ICH | 2\4 | 1y | TO | Y | N | Y | Y | N | Y | – |
| Solitary VS | 45\F | L | 3 cm | Dead ear | FP, FNumb | 3\3 | 2y | ETLA + TA | Y | Y | Y | N | N | Y | – |
| Solitary VS | 62\F | L | 3.2 | Dead ear | Dizziness FNumb | 1\3 | 1.5y | ETLA + TA | Y | N | Y | N | Y | Y | VCP |
| Solitary VS | 49\F | L | 3 cm | 30 DB | HL | 1\3 | 1.5y | ETLA | Y | N | Y | N | N | N | – |
| Solitary VS | 59\M | R | 3.5 | 15DB | Dizziness HL | 1\3 | 2y | ETLA + TA | Y | N | Y | Y | N | N | – |
| Solitary VS | 28\F | R | 4 cm | 20DB | Dizziness HL | 1\1 | 4y | ETLA + TA | Y | Y | N | N | N | N | – |
| Solitary VS | 52\F | R | 2 cm | 60DB | Dizziness HL | 1\3 | 8y | ETLA | Y | N | Y | Y | Y | N | – |
| Solitary VS | 68\F | L | 4 cm | Dead ear | DizzinessFP | 2\3 | 2y | ETLA + TA | Y | Y | Y | Y | N | N | – |
| Solitary VS | 77\M | R | 3.5 cm | 30DB | HL | 1\1 | 1.5y | ETLA | N | Y | Y | N | N | N | – |
| Solitary VS | 47\M | L | 3 cm | Dead ear | Dizziness | 1\3 | 4y | ETLA | Y | N | Y | Y | Y | N | – |
| Solitary VS | 64\M | R | 2.5 cm | Dead ear | Dizziness HL | 1\1 | 1.5y | ETLA | Y | Y | N | N | N | N | – |
| Solitary VS | 59\F | R | 3.2 cm | Dead ear | Dizziness HL | 1\6 | 10y | ETLA + TA | Y | N | Y | Y | Y | N | FN was cut and reconstructed with sural nerve graft that failed |
| Solitary VS | 51\M | L | 3.8 cm | Dead ear | Dizziness | 1\6 | 1.5 y | ETLA + TA | ? | N | Y | Y | Y | N | – |
| NF2 | 40\F | R | 2.4 cm | Dead ear | HL | 1\2 | 1.5y | ETLA + TAABI | Y | N | Y | Y | Y | N | – |
| NF2 | 20\M | L | 3 cm | 55 DB | FP | 4\6 | 5y | TC A + ABI | Y | N | Y | Y | Y | Y | Malignant VS |
The average size of the tumor preoperatively was 3.16 ± 0.57 cm. In all the cases decision of surgery was taken after an increase in tumor size of at least 5 mm with new onset of symptoms.
The methods of radiation therapy were single stage; Gamma Knife was performed in 14 cases and Cyberknife was performed in one case. The interval time between radiotherapy and surgical salvage ranged from 1 to 10 years with a mean of 2.9 years.
The approaches were chosen according to the tumor extension. Extended translabyrinthine approach with or without transapical extension was most commonly used followed by transcochlear type A and transotic approach . Two patients with NF2 underwent brainstem implantation after tumor removal.
The intraoperative findings, postoperative facial nerve outcomes and complications were reviewed. These data were compared with those from a control group who consisted of fifteen patients having vestibular schwannoma treated primarily by surgery during the same period at our institution. These patients were chosen randomly from our computer database in a way that they matched the same range of age, tumor size and surgical approaches of the first group.
To avoid a selection bias 2 patients from the control group having NF2 were selected. All the tumors were resected by the same surgeon (M.S).
The statistical comparisons between the two groups were achieved using the Pearson chi-square test for categorical variables and the Student t-test for continuous variables. Statistical significance was present if P < 0.05, two-tailed.
We performed also a detailed search in PubMed and Medline database with a complete review of all the English literature published until December 2010 regarding surgical salvage of vestibular schwannoma. Papers containing series of five or more patients who underwent surgical salvage of their tumor after failed radiation therapy (including our series) were selected for analysis.
Eight publications complied with our inclusion criteria .
2
Materials and methods
Between April 1983 and December 2010, two thousand three hundred eighty vestibular schwannoma were resected by the senior author (M.S.). After departmental and institutional review board approval, a retrospective chart review was conducted on all cases of VS surgically treated after having received radiation therapy at other centers.
Surgical resection following radiotherapy was performed in nineteen patients. Four patients were excluded from this study because they had previous surgery before radiation therapy. Fifteen patients were included; 6 males and 9 females.
The mean age at surgery was 52 ± 14.8 years [20–77 years]. Two patients had NF 2.
The most common symptoms before surgery were dizziness (60%), worsening of hearing loss (53.3%), facial nerve paralysis (26.6%) and facial numbness (13.3%). One patient presented with intracranial hypertension 1 year following radiotherapy; a VP shunt was inserted and the resection of the tumor was performed 3 weeks later ( Table 1 ).
| Patient | Age\Sex | Side | Size | Hearing Pre | New symptoms | FNG pre\post | Interval time between Rx and surgery | Approach | Total Resection | Plane of cleavage | Excessive Tumor adherence to | Complications and notes | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| FN | BS | Ce | Vth | ||||||||||||
| Solitary VS | 59\F | R | 3.4 cm | Dead ear | FP, ICH | 2\4 | 1y | TO | Y | N | Y | Y | N | Y | – |
| Solitary VS | 45\F | L | 3 cm | Dead ear | FP, FNumb | 3\3 | 2y | ETLA + TA | Y | Y | Y | N | N | Y | – |
| Solitary VS | 62\F | L | 3.2 | Dead ear | Dizziness FNumb | 1\3 | 1.5y | ETLA + TA | Y | N | Y | N | Y | Y | VCP |
| Solitary VS | 49\F | L | 3 cm | 30 DB | HL | 1\3 | 1.5y | ETLA | Y | N | Y | N | N | N | – |
| Solitary VS | 59\M | R | 3.5 | 15DB | Dizziness HL | 1\3 | 2y | ETLA + TA | Y | N | Y | Y | N | N | – |
| Solitary VS | 28\F | R | 4 cm | 20DB | Dizziness HL | 1\1 | 4y | ETLA + TA | Y | Y | N | N | N | N | – |
| Solitary VS | 52\F | R | 2 cm | 60DB | Dizziness HL | 1\3 | 8y | ETLA | Y | N | Y | Y | Y | N | – |
| Solitary VS | 68\F | L | 4 cm | Dead ear | DizzinessFP | 2\3 | 2y | ETLA + TA | Y | Y | Y | Y | N | N | – |
| Solitary VS | 77\M | R | 3.5 cm | 30DB | HL | 1\1 | 1.5y | ETLA | N | Y | Y | N | N | N | – |
| Solitary VS | 47\M | L | 3 cm | Dead ear | Dizziness | 1\3 | 4y | ETLA | Y | N | Y | Y | Y | N | – |
| Solitary VS | 64\M | R | 2.5 cm | Dead ear | Dizziness HL | 1\1 | 1.5y | ETLA | Y | Y | N | N | N | N | – |
| Solitary VS | 59\F | R | 3.2 cm | Dead ear | Dizziness HL | 1\6 | 10y | ETLA + TA | Y | N | Y | Y | Y | N | FN was cut and reconstructed with sural nerve graft that failed |
| Solitary VS | 51\M | L | 3.8 cm | Dead ear | Dizziness | 1\6 | 1.5 y | ETLA + TA | ? | N | Y | Y | Y | N | – |
| NF2 | 40\F | R | 2.4 cm | Dead ear | HL | 1\2 | 1.5y | ETLA + TAABI | Y | N | Y | Y | Y | N | – |
| NF2 | 20\M | L | 3 cm | 55 DB | FP | 4\6 | 5y | TC A + ABI | Y | N | Y | Y | Y | Y | Malignant VS |
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