Current dosing paradigm for stereotactic radiosurgery alone after surgical resection of brain metastases needs to be optimized for improved local control.
ABSTRACT To describe the use of radiosurgery (RS) alone to the resection cavity after resection of brain metastases as an alternative to adjuvant whole-brain radiotherapy (WBRT).
Sixty-two patients with 64 cavities were treated with linear accelerator-based RS alone to the resection cavity after surgical removal of brain metastases between March 2007 and August 2010. Fifty-two patients (81%) had a gross total resection. Median cavity volume was 8.5 cm(3). Forty-four patients (71%) had a single metastasis. Median marginal and maximum doses were 18 Gy and 20.4 Gy, respectively. Sixty-one cavities (95%) had gross tumor volume to planning target volume expansion of ≥1 mm.
Six-month and 1-year actuarial local recurrence rates were 14% and 22%, respectively, with a median follow-up period of 9.7 months. Six-month and 1-year actuarial distant brain recurrence, total intracranial recurrence, and freedom from WBRT rates were 31% and 51%, 41% and 63%, and 91% and 74%, respectively. The symptomatic cavity radiation necrosis rate was 8%, with 2 patients (3%) undergoing surgery. Of the 11 local failures, 8 were in-field, 1 was marginal, and 2 were both (defined as in-field if ≥90% of recurrence within the prescription isodose and marginal if ≥90% outside of the prescription isodose).
The high rate of in-field cavity failure suggests that geographic misses with highly conformal RS are not a major contributor to local recurrence. The current dosing regimen derived from Radiation Therapy Oncology Group protocol 90-05 should be optimized in this patient population before any direct comparison with WBRT.
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ABSTRACT: Purpose To investigate how millimeter-level margins beyond the gross tumor volume (GTV) impact peripheral normal brain tissue sparing for Gamma Knife radiosurgery. Methods and Materials A mathematical formula was derived to predict the peripheral isodose volume, such as the 12-Gy isodose volume, with increasing margins by millimeters. The empirical parameters of the formula were derived from a cohort of brain tumor and surgical tumor resection cavity cases (n=15) treated with the Gamma Knife Perfexion. This was done by first adding margins from 0.5 to 3.0 mm to each individual target and then creating for each expanded target a series of treatment plans of nearly identical quality as the original plan. Finally, the formula was integrated with a published logistic regression model to estimate the treatment-induced complication rate for stereotactic radiosurgery when millimeter-level margins are added. Results Confirmatory correlation between the nominal target radius (ie, RT) and commonly used maximum target size was found for the studied cases, except for a few outliers. The peripheral isodose volume such as the 12-Gy volume was found to increase exponentially with increasing Δ/RT, where Δ is the margin size. Such a curve fitted the data (logarithmic regression, R2 >0.99), and the 12-Gy isodose volume was shown to increase steeply with a 0.5- to 3.0-mm margin applied to a target. For example, a 2-mm margin on average resulted in an increase of 55% ± 16% in the 12-Gy volume; this corresponded to an increase in the symptomatic necrosis rate of 6% to 25%, depending on the Δ/RT values for the target. Conclusions Millimeter-level margins beyond the GTV significantly impact peripheral normal brain sparing and should be applied with caution. Our model provides a rapid estimate of such an effect, particularly for large and/or irregularly shaped targets.International journal of radiation oncology, biology, physics 01/2014; 89(1):206–213. · 4.59 Impact Factor
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ABSTRACT: Following surgical resection for brain metastases, fractionated stereotactic radiotherapy (FSRT) has been used as an alternative to single dose treatment for large cavities and to reduce risks of late toxicity. The purpose of this study was to evaluate the outcomes of patients treated with FSRT to the post-operative bed for both radioresistant and radiosensitive brain metastases. Between December 2009 and May 2013 a total of 65 patients with newly diagnosed brain metastases were treated with resection followed by FSRT. Patients were treated to a total dose of 20-30 Gy in five fractions. Median planning target volume (PTV) was 16.88 cm(3) (range 4.87-128.43 cm(3)). The median follow-up for all patients was 8.5 months (range 1.1-28.6 months) with a median of 12.9 months for living patients. One and two year Kaplan-Meier estimates of local control were 87.0 and 70.0 %, respectively. Local control at 1 year was 85.6 and 88.0 % for radioresistant and radiosensitive tumors, respectively (p = 0.44). A PTV ≥17 cm(3), was associated with local failure, HR 8.63 ((1.44-164.78); p = 0.02). One and two year distant control rates were 50.9 and 46.2 %, respectively with six patients (9.2 %) experiencing leptomeningeal disease. OS rates at 1 and 2 years were 65.2 and 47.5 %, respectively. Survival was significantly associated with recursive partitioning analysis class (p = 0.001) and graded prognostic assessment score (p = 0.005). One case of radionecrosis was noted on follow-up imaging. FSRT in five fractions offers excellent local control in both radiosensitive and radioresistant tumors with minimal toxicity.Journal of Neuro-Oncology 03/2014; · 3.12 Impact Factor
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ABSTRACT: Esophageal carcinoma rarely results in intracranial metastases but when it does, the patient prognosis is grim. Because of its rarity outcomes after stereotactic radiosurgery (SRS) are not known. We sought to evaluate the outcomes of SRS in the management of esophageal cancer that has spread to the brain. This single institution retrospective analysis reviewed our experience with esophageal metastasis from 1987 to 2013. Thirty patients (36 SRS procedures) with a median age of 59 (37-86 years) underwent Gamma knife(®) SRS. The esophageal origin was adenocarcinoma in 26 patients (87 %), squamous cell carcinoma in 3 patients (10 %), and mixed neuroendocrine carcinoma in 1 patient (3 %). Fifteen patients were treated for a single metastasis and 15 patients were treated for multiple metastases for a total of 87 tumors. The median tumor volume was 5.7 cm(3) (0.5-44 cm(3)) with a median marginal dose of 17 Gy (12-20 Gy). The median survival time from the diagnosis of brain metastasis was 8 months and the median survival from SRS was 4.2 months. This corresponded to a 6-month survival of 45 % and a 12-month survival of 19 % after SRS. A higher KPS at the time of procedure was associated with an increase in survival (p = 0.023). The local tumor control rate in this group was 92 %. Four patients had repeat SRS for new metastatic deposits. One patient developed a new neurological deficit after SRS. SRS proved an effective means of providing local control for esophageal metastases to the brain. Concomitant systemic disease progression at the time of brain metastasis resulted in poor long-term survival.Journal of Neuro-Oncology 04/2014; · 3.12 Impact Factor