Radiosurgery for brain tumours

A Systematic Review of Radiosurgery Versus Surgery for Neurofibromatosis Type 2 Vestibular Schwannomas

OBJECTIVE

Neurofibromatosis type 2 (NF2) is an autosomal dominant disease characterized by bilateral vestibular schwannomas (VSs). NF2-associated VSs (NF2-VSs) are routinely treated with microsurgery; however, stereotactic radiosurgery (SRS) has emerged as an effective alternative in recent decades. To elucidate the role of SRS in NF2-VSs, a systematic review of the literature was conducted to compare outcomes of SRS versus surgery.

METHODS

PubMed, Web of Science, Scopus, Embase, and Cochrane databases were queried using relevant search terms. Retrospective studies investigating outcomes of NF2-VS patients treated with either SRS or surgery were included. Single-patient case reports were excluded. Outcome measures between the SRS and surgery groups were compared using χ² 2-sample tests for equality of proportions on the pooled patient data.

RESULTS

A total of 974 patients (485 SRS, 489 surgery) were identified. The mean 5-year local control rate for SRS was 75.1%, and the mean recurrence rate for surgery was 8.1%. The mean hearing and facial nerve preservation rates were 40.1% and 92.3%, respectively, for SRS and 52.0% and 75.7%, respectively, for surgery. Rates of hearing preservation were higher after surgery than after SRS (P = 0.006), whereas rates of facial nerve preservation were higher after SRS than after surgery (P < 0.001).

CONCLUSIONS

SRS appears to be a safe and effective alternative to surgery for NF2-VS. Although rates of hearing preservation were higher in the surgery cohorts, SRS demonstrated high rates of local control and significantly lower facial nerve complications. Certain patients may therefore benefit more from SRS than surgery.

Intracranial osteosarcoma after radiosurgery--case report

A 56-year-old woman presented with an intracranial osteosarcoma at the site of previous radiosurgery, manifesting as sudden onset of headache and left hemiparesis with aphasia. She had a previous history of stereotactic radiosurgery for an intracranial tumor under a diagnosis of falx meningioma. Computed tomography showed intratumoral and peritumoral hemorrhage at the right parietofrontal region. Gross total resection of the tumor with hematoma was performed. The histological diagnosis was osteosarcoma. Sarcomatous change is a rare complication of radiotherapy. This case illustrates that osteosarcoma may develop years after radiosurgery for benign brain neoplasm.

Stereotactic radiosurgery in the management of intracranial gliomas

Glial neoplasms are the most common primary intracranial malignancies. Treatment of high-grade gliomas has been frustrating, with less than 5% of patients surviving 5 years after a diagnosis of glioblastoma multiforme (GBM). Stereotactic radiosurgery (SRS) and fractionated strereotactic radiotherapy (F-SRT) provide means to either escalate the dose in primary treatment or to palliate recurrences. Because of their lower alpha/beta ratios and more focal nature, low-grade gliomas (LGG) are more attractive targets for stereotactically focused radiation. Results of available phase I-II data are reviewed for both low and high-grade gliomas. In the case of high-grade gliomas disappointing preliminary phase III data from RTOG 93-05 are discussed. Toxicity of SRS is discussed. Acute treatment toxicity of significance is unusual and generally self-limited. Occasionally an exacerbation of existing symptoms occurs. Late complications attributable to SRS are usually defined as necrosis within the treatment volume. The rate of necrosis can be hard to define in high-grade gliomas as tumor cells are often present in surgical specimens. New strategies in the application of stereotactic radiation are touched upon, these include: changes in planning and fractionation, concurrent use of chemotherapy, use of radiation modifiers and biologic agents. After reviewing the current data for high-grade gliomas, it appears that any apparent improvement in outcome seen in phase I-II trials is attributable to patient selection. The best evidence available does not support the use of SRS for primary high-grade gliomas. The somewhat limited experience in LGG also indicates a lack of benefit for patients treated with stereotactic radiosurgery or F-SRT. For a very select group of patients with small recurrent lesions, F-SRT may represent a safe, reasonable treatment.

Radiosurgery/stereotactic external beam radiotherapy for malignant brain tumours: the Royal Marsden Hospital experience

SRT is a high-precision technique of radiotherapy which delivers focused irradiation to small target volumes. In the context of external beam radiotherapy it can be described as stereotactically guided conformal radiotherapy. As the technique originated from neurosurgical technology, it has initially been limited to single fraction treatment. However, with the use of relocatable fixation devices the way ahead particularly in its application in the treatment of brain tumours is in fractionated SRT. Currently, single fraction SRT/radiosurgery is of proven value only in the treatment of small inoperable arteriovenous malformations. It is being exploited in the management of brain tumours but so far remains as experimental treatment. We have demonstrated that fractionated SRT in patients with gliomas is a non-invasive equivalent to brachytherapy and in patients with solitary metastases a non-invasive alternative to surgical excision. However, the treatment is not without side effects, and the long-term effectiveness and toxicity of SRT, particularly with the use of unconventional fractionation, is not defined. The future use of SRT in the treatment of brain tumours should not be guided simply by the technical possibilities but by a rational appraisal of all treatment options to achieve the best disease control, survival and toxicity. Although there is potential for benefit in a number of small tumours, SRT cannot at present be recommended as the primary treatment in any tumour. In addition, its use should be discouraged in the treatment of unbiopsied brain lesions and as the major form of treatment of pineal germinomas. The technology of stereotactic radiotherapy is evolving, and it is likely that SRT will be integrated into conventional radiotherapy practice to become simply a high-precision technique of radiotherapy delivery in everyday use.