Modern Neurosurgery of Meningiomas and Pituitary Adenomas (Acta Neurochirurgica Supplement)
As we continue to accrue long-term follow up for patients treated with radiation in conjunction with, or as an alternative to surgery, it is apparent that radiation therapy represents a valuable tool in the treatment of the various presentations of WHO grade I meningioma. Multiple treatment techniques including stereotactic radiosurgery SRS , fractionated external beam radiation therapy, and particle therapy using protons have been used successfully for the treatment of these tumors.
The use of radiation for the treatment of WHO grade I meningiomas will be reviewed here. Simpson grading depends on intraoperative observations and categorizes resection quality along a scale from 1—5. A Simpson 1 resection removes all tumor, associated dural attachments and involved bone, whereas a Simpson 5 resection is simple decompression only.
In most studies, a Simpson grade 1—3 resection is considered a GTR 5 , 6. Successfully achieving GTR has been an important prognostic factor in patients with all grades of meningioma 6 , with STR resulting in increased risk of recurrence 7 , 8. There remains controversy regarding whether patients with meningioma after STR should undergo active surveillance or radiation therapy. Some studies have suggested that small amounts of residual tumor can be observed with high PFS rates.
For example, a analysis by Sughrue et al.
Thus, patients with advanced age or multiple comorbidities and small residual tumor may not recur, or perhaps more importantly, may not grow enough to cause symptoms. However, others argue that especially in young patients with tumor locations that are likely to become symptomatic, adjuvant radiation therapy is indicated. Multiple observational studies have demonstrated the benefit of fractionated EBRT in the adjuvant setting following STR of benign meningioma.
Furthermore, certain series suggest that there may be a survival benefit to adjuvant radiation therapy after STR. Condra and colleagues noted that STR significantly affected cause specific survival CSS in patients with benign meningioma. Of note, this work likely included patients that would now be categorized as WHO grade II, thus potentially overestimating the true benefit of radiation in the lowest risk patients. The median age in this series was 56 years and median follow up was 75 months Though most of the early series utilized standard external beam radiation therapy with margins added, more recent series have used improved imaging and targeting capabilities with stereotactic localization to successfully treat skull base tumors with higher precision.
Patients in these studies were generally treated using fractions of 1. Radiation therapy has emerged as a viable alternative when the patient has a surgically inaccessible tumor, is medically inoperable, or prefers radiation therapy over surgical intervention. Initially, radiation therapy was used in tumors that were not surgically accessible.
For instance, though initially surgical resection was pursued for optic nerve sheath meningiomas, high rates of blindness were associated with optic nerve infarction during surgery 33 , Thus, standard fractionated external beam radiation therapy to 50—54 Gy was utilized. Similarly, surgical resection of cavernous sinus meningioma was often associated with cranial neuropathies and thus multiple series outline good outcomes after radiation therapy alone, either standard fractionated external beam radiation therapy or stereotactic radiosurgery 28 , 38 - These experiences led to the successful treatment of meningioma with radiation therapy in other locations and for patients who were medically inoperable or preferred radiation therapy over surgical resection.
The increase in use of SRS has also been influenced by the increase in the number of radiographically detected, clinically occult lesions being discovered in the era of widespread medical imaging 5 , Many of these asymptomatic lesions are small enough for active surveillance or treatment with SRS.http://convecon.xtage.com.br/15077-donde-conocer-mujeres.php
Modern Neurosurgery of Meningiomas and Pituitary Adenomas - Semantic Scholar
Statistically, most of these incidental lesions are be WHO grade I meningiomas, and success in treating imaging-defined meningioma suggests that radiotherapy may be effective in a majority of cases. Given the slow growth of these tumors and the possibility of late recurrence, longer term follow-up is warranted, but the evidence supporting the use of primary radiotherapy in imaging defined meningioma is accumulating. One of the largest studies published is a retrospective analysis of more than 4, patients with a median follow-up of 63 months.
It included approximately imaging-defined meningiomas treated with radiosurgery alone and tumor control, defined as a reduction in volume or stable size, was Though initial experience with radiation therapy included standard external beam radiation therapy, in an effort to minimize toxicity including long-term effects clinicians began using more precisely targeted approaches. This was facilitated by advances in imaging including the more prevalent use of magnetic resonance imaging MRI and in stereotactic delivery including cobalt machines, linear accelerators, robotic linear accelerators, and proton therapy.
Throughout the s, reports on standard external beam radiation therapy for meningioma were published. Typically SRS is reserved for tumors that are less than 3 cm in diameter or about 10 cm 3 in volume. Multiple studies have suggested that efficacy is based on tumor size. For instance, DiBiase and colleagues reported a 5-year disease free survival of In addition, toxicity is quite dependent on size.
Pollack and colleagues reported on a year experience with SRS for presumed meningioma, with complication rates of 4. For larger tumors or those that are close to dose limiting normal structures such as the optic nerves and chiasm, fractionated radiation therapy has been most used.
However, there are increasing reports of multisession stereotactic radiation therapy utilizing many of the same platforms used for SRS 53 , 60 - These studies demonstrate comparable local control compared to single fraction treatment and its proponents argue that side effects may be fewer. The median dose for SRS was 15 Gy and the usual regimen was 25 Gy in 5 fractions for multisession stereotactic radiation therapy.
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Modern Neurosurgery of Meningiomas and Pituitary Adenomas
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Alfieri A, Jho HD. Endoscopic endonasal approaches to the cavernous sinus: Surgical approaches. Endoscopic extradural subtemporal approach to lateral and central skull base: A cadaveric study.
World Neurosurg ; Users Online: Review of surgical anatomy of the tumors involving cavernous sinus. Asian J Neurosurg ; Figure 1: Cavernous sinus tumors can be divided into three types: a Type-I: The tumor originating from the cavernous sinus area, b Type-II: From the lateral wall of cavernous sinus, c and d Type-III: Extraneous origin and compressing the cavernous sinus, and d invading the cavernous sinus wall Click here to view. Figure 2: a-c T1-weighted magnetic resonance imaging demonstrating the cavernous hemangioma in cavernous sinus Type-I , d T1-weighted magnetic resonance imaging demonstrating the trigeminal neurinoma extending to and between the lateral wall of cavernous sinus Type-II , e sphenoid wing meningioma extending to the lateral cavernous sinus wall Type-III , f nasopharyngeal carcinoma invading the cavernous sinus Type-III Click here to view.
Figure 4: a Intraoperative view of the meningioma from the right petrous apex, compressing cavernous sinus, without invading the wall of cavernous sinus Type-III ; b Intraoperative view of chordoma invading the cavernous sinus through posterior cavernous sinus wall Type-III ; c intraoperative view showing the tumor after opening outer cavernous sinus wall; VII-Cranial nerve VII. Related articles Anatomy cavernous sinus meningioma tumors.