Stereotactic radiosurgery in the management of intracranial gliomas

Indications and Efficacy of Gamma Knife Stereotactic Radiosurgery for Recurrent Glioblastoma: 2 Decades of Institutional Experience

BACKGROUND

The role of stereotactic radiosurgery (SRS) for recurrent glioblastoma and the radionecrosis risk in this setting remain unclear.

OBJECTIVE

To perform a large retrospective study to help inform proper indications, efficacy, and anticipated complications of SRS for recurrent glioblastoma.

METHODS

We retrospectively analyzed patients who underwent Gamma Knife SRS between 1991 and 2013. We used the partitioning deletion/substitution/addition algorithm to identify potential predictor covariate cut points and Kaplan-Meier and proportional hazards modeling to identify factors associated with post-SRS and postdiagnosis survival.

RESULTS

One hundred seventy-four glioblastoma patients (median age, 54.1 years) underwent SRS a median of 8.7 months after initial diagnosis. Seventy-five percent had 1 treatment target (range, 1-6), and median target volume and prescriptions were 7.0 cm 3 (range, 0.3-39.0 cm 3 ) and 16.0 Gy (range, 10-22 Gy), respectively. Median overall survival was 10.6 months after SRS and 19.1 months after diagnosis. Kaplan-Meier and multivariable modeling revealed that younger age at SRS, higher prescription dose, and longer interval between original surgery and SRS are significantly associated with improved post-SRS survival. Forty-six patients (26%) underwent salvage craniotomy after SRS, with 63% showing radionecrosis or mixed tumor/necrosis vs 35% showing purely recurrent tumor. The necrosis/mixed group had lower mean isodose prescription compared with the tumor group (16.2 vs 17.8 Gy; P = .003) and larger mean treatment volume (10.0 vs 5.4 cm 3 ; P = .009).

CONCLUSION

Gamma Knife may benefit a subset of focally recurrent patients, particularly those who are younger with smaller recurrences. Higher prescriptions are associated with improved post-SRS survival and do not seem to have greater risk of symptomatic treatment effect.

CyberKnife Stereotactic Radiosurgery for Intracranial Neoplasms, with a Focus on Malignant Tumors

Stereotactic radiosurgery is well established as a means of managing intracranial tumors, both as an adjuvant to surgical resection, and also as a primary treatment modality for those tumors that are considered unresectable by conventional surgical means. Of particular concern during radiosurgery of brain tumors is the risk of radiation damage to otherwise healthy tissue, potentially resulting in cognitive impairment. The conformality and precise targeting of the CyberKnife radiation beam enables this risk to be minimized to a greater extent than hitherto possible, which may allow treatment to be completed in a small number of fractions, thereby improving the quality of life for patients. The CyberKnife has proven particularly valuable in the treatment of metastases, which represent the great majority of brain tumors, though its role in the management of malignant glial tumors remains a subject of controversy. This article reviews the published studies on the efficacy of CyberKnife radiosurgery for brain tumors of both glial and metastatic origin, and considers its future role in the management of such lesions.

Is there a place for radiotherapy in low-grade gliomas?

The optimal management of supratentorial low-grade glioma remains controversial, and only limited definitive data is available to guide recommendations. Treatment decisions have to take into account both the management of symptoms and of tumour control, and must balance the benefits against the potential for treatment-related complications. Overall outcome is more dependent on patient and tumour-related characteristics such as age, tumour grade, histology and neurological function than treatment. From the pooled analysis of 2 randomized EORTC trials a prognostic score has been derived, median survival is varying from 3.2 to 7.8 years. Radiation therapy is usually the primary treatment modality; however its benefit on initial tumour control may be outweighed by potential late toxicity. To date only 4 large randomized trials in patients with low-grade glioma have been reported. It allows concluding that early radiotherapy does not improve overall survival and supports an initially expectative approach. Similarly, higher radiation doses above 45-50 Gy (fractions of 1.8-2.0 Gy) do not confer a better outcome but may be associated with increased toxicity. The adjuvant use of PCV-chemotherapy in high-risk patients also failed to improve progression-free and overall survival. An ongoing large randomized EORTC/NCIC trial is investigating the primary treatment with temozolomide chemotherapy versus standard radiotherapy in patients "at need for treatment". Tumour material will be collected in all patients, which ultimately may allow identifying on a molecular basis patients for whom one or another treatment strategy may fit best. Irrespective of new chemotherapeutic agents, radiotherapy is also evolving. Highly conformal techniques based on modern imaging as co-registered MRI scans, limiting the amount of normal tissue irradiated without compromising tumour control, will be the future approach in order to reduce neurotoxicity.

Survival following stereotactic radiosurgery for newly diagnosed and recurrent glioblastoma multiforme: a multicenter experience

Despite decades of clinical trials investigating new treatment modalities for glioblastoma multiforme (GBM), there have been no significant treatment advances since the 1980s. Reported median survival times for patients with GBM treated with current modalities generally range from 9 to 19 months. The purpose of the current study is to retrospectively review the ability of CyberKnife (Accuray Incorporated, Sunnyvale, CA, USA) radiosurgery to provide local tumor control of newly diagnosed or recurrent GBM. Twenty patients (43.5%) underwent CyberKnife treatment at the time of the initial diagnosis and/or during the first 3 months of their initial clinical management. Twenty-six patients (56.5%) were treated at the time of tumor recurrence or progression. CyberKnife was performed in addition to the traditional therapy. The median survival from diagnosis for the patients treated with CyberKnife as an initial clinical therapy was 11.5 months (range, 2-33) compared to 21 months (range, 8-96) for the patients treated at the time of tumor recurrence/progression. This difference was statistically significant (Kaplan-Meier analysis, P = 0.0004). The median survival from the CyberKnife treatment was 9.5 months (range, 0.25-31 months) and 7 months (range, 1-34 months) for patients in the newly diagnosed and recurrent GBM groups (Kaplan-Meier analysis, P = 0.79), respectively. Cox proportional hazards survival regression analysis demonstrated that survival time did not correlate significantly with treatment parameters (Dmax, Dmin, number of fractions) or target volume. Survival time and recursive partitioning analysis class were not correlated (P = 0.07). Patients with more extensive surgical interventions survived longer (P = 0.008), especially those who underwent total tumor resection vs. biopsy (P = 0.004). There is no apparent survival advantage in using CyberKnife in initial management of glioblastoma patients, and it should be reserved for patients whose tumors recur or progress after conventional therapy.

Survival following CyberKnife radiosurgery and hypofractionated radiotherapy for newly diagnosed glioblastoma multiforme

Current therapeutic goals for treatment of Glioblastoma Multiforme (GBM) involve gross total resection followed by multifractionated focal external beam radiation therapy (EBRT). Patients treated with optimal therapy have a median survival of approximately 12-15 months. In the present study, we sought to determine whether a hypofractionated dosing schedule using CyberKnife is at least as effective as multifractionated focal EBRT. A retrospective analysis was conducted on 20 histopathologically confirmed GBM patients treated with CyberKnife at Okayama Kyokuto Hospital in Japan after gross total resection (n=11), subtotal resection (n=8), or biopsy (n=1). Eight patients also received adjuvant ACNU and Vincrisitine chemotherapy according to local protocol; however, no patient received any other form of radiation besides post surgical/biopsy CyberKnife treatment. The treated tumor volumes ranged from 9.62 cm(3)-185.81 cm(3) (mean: 86.08 cm(3)). The marginal dose (D90) ranged from 19.99 Gy-41.47 Gy (mean: 34.58 Gy) with a maximum mean dose of 43.99 Gy (range: 23.33 Gy-56.89 Gy). The prescribed isodose line ranged from 50.38%-85.68% with a mean of 79.25%. Treatment was delivered in 1-8 fractions (mean: 5.65). Patients were followed from 2-36 months (mean: 16.45 months). Overall median survival was 16 months with 55% of patients alive at 12 months and 34% of patients alive at 24 months. Median survival of patients in Recursive Partitioning Analysis (RPA) classes III or IV was 32 months versus 12 months for those in RPA class V. Median survival for patients who received gross total resection was 36 months versus 8 months for those who underwent subtotal resection or biopsy. The results of this study using CyberKnife stereotactic radiosurgery (SRS) and hypofractionated radiotherapy compared favorably to historic data using focal EBRT in newly diagnosed post surgical GBM patients. A larger prospective analysis that compares CyberKnife SRS and hypofractionated radiotherapy to focal EBRT is warranted.

Stereotactic radiosurgery: indications and results - part 2

Stereotactic radiosurgery and fractionated stereotactic radiotherapy represent an increasingly important option in the treatment of central nervous system disease. In this article, we discuss indications for stereotactic radiosurgery and review results reported in the medical literature.

Radiosurgery in the Treatment of Malignant Gliomas: The University of Florida Experience

OBJECTIVE:

To review a single-institution's 12-year experience of treating malignant gliomas with linear accelerator-based radiosurgery.

METHODS:

One hundred patients were treated for malignant gliomas at the University of Florida between May 1, 1989, and June 12, 2002. Patient variables were entered into a radiosurgery database in a prospective manner. The endpoint of the study was length of survival from the time of diagnosis. The minimum length of follow-up was 18 months or until death. In an attempt to control for selection bias, we used the Radiation Oncology Therapy Group's (RTOG) recursive partitioning categories to compare survival in our group of radiosurgically boosted patients with the RTOG historical database.

RESULTS:

Recursive partitioning analysis classification was significantly associated with survival. Compared with historical controls, this cohort of patients demonstrated a decreased survival for recursive partitioning analysis Class I and II patients, similar survival for Class III and IV patients, and increased median survival for Class V patients. Other variables demonstrating a statistically significant impact on survival were eloquent location and recurrent disease.

CONCLUSION:

The results of this study and those of RTOG 93-05 suggest that the reported benefit of upfront radiosurgical boost for malignant gliomas is the result of selection bias. The possibility remains that radiosurgical boost is of benefit in recurrent tumors, especially those in RTOG Class V.

Update of stereotactic radiosurgery for brain tumors

PURPOSE OF REVIEW

This paper will review the recent publications of stereotactic radiosurgery for brain tumors.

RECENT ADVANCES

Despite its controversial beginning, stereotactic radiosurgery has rapidly gained acceptance among neurosurgeons, radiation oncologists, and neuro-oncologists as a valuable treatment option for patients with certain benign and malignant brain tumors. Over the past year, a number of publications have confirmed the efficacy and safety of this treatment modality as the sole treatment modality or as part of the multimodality management of brain tumor patients. These publications ranged from the first multi-institutional phase III trial of radiosurgery for patients with brain metastases to numerous retrospective papers about treatment outcomes. Also, a number of these publications have explored the use of newer imaging modalities to improve treatment outcomes while others reported on the rare complication of radiation-associated second tumors.

SUMMARY

Recent publications of stereotactic radiosurgery have increased our understanding of the use of this technology. Future studies are needed to further improve outcomes, minimize toxicities and increase our understanding of this treatment modality.