Kidney Cancer Journal 77 SAbR for CNS RCC Metastases Gamma knife surgery (GKS) for metastatic brain tumors from RCC has a long history since stereotaxis initially was invented and designed for intracranial lesions, beginning with the first report published more than 20 years ago. Recent studies, however, are not only building on the previous track record of successful results but elucidating additional benefits that may accrue from such radiosurgery, including improved tumor reduction and long-term survival. These reports are exploring some of the underappreciated nuances of GKS in this setting. To what extent is GSK effective for growth control of metastatic tumors and what effect can it have on peritumoral edema control? This question was addressed in a retrospective report by Shuto et al studying 280 metastatic brain tumors—80 from RCC and others involving breast and lung. In addition, the authors included 11 patients with metastatic brain tumors from RCC who had direct surgery. After compiling the data, Shuto et al17 present a treatment algorithm with a recommended strategy depending on tumor size, toleration of general anesthesia, presence of symptomatic peritumoral edema, and number of tumors. The retrospective findings suggested “The application of SAbR is currently the standard of care for CNS and spine metastases from RCC where surgery is difficult and morbid. Additional indications currently under investigation include SAbR for oligometastatic and oligoprogressive mRCC and neoadjuvant treatment for IVC a tumor growth control rate of 84.3%. The key findings: The primary site (renal or not renal) and the delivered marginal dose (25 Gy or more) were significantly correlated with control of peritumoral edema; although peritumoral edema was extensive, it disappeared within 1-3 months. All tumors treated with direct surgery were 2 cm in maximum diameter. Significant total tumor volume reduction at an early treatment seems to result in long-term survival, according to Kim et al, who proposed prognostic factors worth considering in determining outcomes. The median survival time for 46 patients in a study spanning 12 years was 18 months in the good response group, significantly longer than that observed in the poor response group (9 months. P=0.025). After treatment, local tumor control was achieved in 84.7% of the 85 tumors assessed. Classification in the “good-response” group was the only independent prognostic factor for longer survival. Although the study did not specifically address the effect of total tumor volume reduction on quality of life, the authors suggest that such reduction can lead to improved neurologic symptoms and patients may be better able to undergo systemic therapy. Spine Radiosurgery: Emerging Issues, Guidelines Spine radiosurgery is an effective tool in manag ing patients with RCC. Although RT has little role in the treatment of primary disease, SRS does play an important role in the treatment of patients with spinal metastases, particularly those who received prior RT or instrumentation according to Taunk et al.37 It is known from multiple series that spine SRS for RCC has extremely high rates of durable local control and palliation. However, it demands high quality control, precision guidance, and careful patient selection in multi-modality consultations to be safely and effectively implemented. SAbR requires several special techniques to de liver ablative RT safely and effectively, including (1) use of multiple conformal beams with intensity-modulation, (2) accuracy within millimeters, (3) im age guidance with each treatment, and (4) custom immobilization. Multiple beams allow for shaping of highly conformal dose, particularly sparing the spinal cord, which is usually within millimeters of the target volume. Custom immobilization requires comfortable, reproducible patient positioning while se- curely immobilizing the shoulders, neck, abdomen, or pelvis, as needed. Image guidance uses daily on-board imaging, ideally with pretreatment conebeam CT.38 Between 2004 and 2010, MSKCC treated 105 RCC metastases (59 spine lesions) with single-dose SRS or hypofractionated SRS. The overall 3-year ac tuarial local progression-free survival rate was 44%. In patients with disease treated in a single fraction and with a dose of 24 Gy or greater, the 3-year local progressionfree survival rate was 88%. In contrast, patients receiving hypofractionated treatment in 3 or 5 fractions had a 3- year local control rate of 17%. Treatment delivered in a single fraction and with a dose of 24 Gy or greater significantly improved local control in multivariate analysis.20 The authors’ practice is to recommend SRS alone in patients with oligometastatic disease and mechanically stable spines. Operating in the NOMS (Neurologic, Oncologic, Mechanical instability, and Systemic disease) clinical framework, patients with spine lesions are assessed in a multidisciplinary clinic at MSKCC by a radiation oncologist, spine neurosurgeon, and neurointerventional radiologist. Careful patient selection is critical to identify those who may benefit the most from treatment, includ ing patients for whom prior radiation treatment failed. Indicated procedures are performed for stabilization using implanted hardware or kyphoplasty before ra diation. Patients with RCC who present with high-grade spinal cord compression often require surgical decompression and stabilization to separate the tu mor from the spinal cord and facilitate delivery of SRS while remaining within spinal cord tolerance. Stereotactic Radiotherapy for Extra-CNS Oligometastases Although the evidence is relatively sparse compared to other treatment settings, data are growing and suggest compelling results for the use of SAbR in RCC extracranial tumor thrombus.”
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