Single-fraction Radiosurgery Research Articles

Hypofractionated radiosurgery for intact or resected brain metastases: defining the optimal dose and fractionation

BackgroundHypofractionated Radiosurgery (HR) is a therapeutic option for delivering partial brain radiotherapy (RT) to large brain metastases or resection cavities otherwise not amenable to single fraction radiosurgery (SRS). The use, safety and efficacy of HR for brain metastases is not well characterized and the optimal RT dose-fractionation schedule is undefined.MethodsForty-two patients treated with HR in 3-5 fractions for 20 (48%) intact and 22 (52%) resected brain metastases with a median maximum dimension of 3.9 cm (0.8-6.4 cm) between May 2008 and August 2011 were reviewed. Twenty-two patients (52%) had received prior radiation therapy. Local (LC), intracranial progression free survival (PFS) and overall survival (OS) are reported and analyzed for relationship to multiple RT variables through Cox-regression analysis.ResultsThe most common dose-fractionation schedules were 21 Gy in 3 fractions (67%), 24 Gy in 4 fractions (14%) and 30 Gy in 5 fractions (12%). After a median follow-up time of 15 months (range 2-41), local failure occurred in 13 patients (29%) and was a first site of failure in 6 patients (14%). Kaplan-Meier estimates of 1 year LC, intracranial PFS, and OS are: 61% (95% CI 0.53 – 0.70), 55% (95% CI 0.47 – 0.63), and 73% (95% CI 0.65 – 0.79), respectively. Local tumor control was negatively associated with PTV volume (p = 0.007) and was a significant predictor of OS (HR 0.57, 95% CI 0.33 - 0.98, p = 0.04). Symptomatic radiation necrosis occurred in 3 patients (7%).ConclusionsHR is well tolerated in both new and recurrent, previously irradiated intact or resected brain metastases. Local control is negatively associated with PTV volume and a significant predictor of overall survival, suggesting a need for dose escalation when using HR for large intracranial lesions.

Single fraction radiosurgery using RapidArc® for the treatment of intracranial metastases

Single fraction radiosurgery using RapidArc® for the treatment of intracranial metastases

Five Fraction Image-Guided Radiosurgery for Primary and Recurrent Meningiomas

Purpose: Benign tumors that arise from the meninges can be difficult to treat due to their potentially large size and proximity to critical structures such as cranial nerves and sinuses. Single fraction radiosurgery may increase the risk of symptomatic peritumoral edema. In this study, we report our results on the efficacy and safety of five fraction image-guided radiosurgery for benign meningiomas.Materials/Methods: Clinical and radiographic data from 38 patients treated with five fraction radiosurgery were reviewed retrospectively. Mean tumor volume was 3.83 mm3 (range, 1.08–20.79 mm3). Radiation was delivered using the CyberKnife, a frameless robotic image-guided radiosurgery system with a median total dose of 25 Gy (range, 25–35 Gy).Results: The median follow-up was 20 months. Acute toxicity was minimal with eight patients (21%) requiring a short course of steroids for headache at the end of treatment. Pre-treatment neurological symptoms were present in 24 patients (63.2%). Post treatment, neurological symptoms resolved completely in 14 patients (58.3%), and were persistent in eight patients (33.3%). There were no local failures, 24 tumors remained stable (64%) and 14 regressed (36%). Pre-treatment peritumoral edema was observed in five patients (13.2%). Post-treatment asymptomatic peritumoral edema developed in five additional patients (13.2%). On multivariate analysis, pre-treatment peritumoral edema and location adjacent to a large vein were significant risk factors for radiographic post-treatment edema (p = 0.001 and p = 0.026 respectively).Conclusion: These results suggest that five fraction image-guided radiosurgery is well tolerated with a response rate for neurologic symptoms that is similar to other standard treatment options. Rates of peritumoral edema and new cranial nerve deficits following five fraction radiosurgery were low. Longer follow-up is required to validate the safety and long-term effectiveness of this treatment approach.

Visual acuity after Gamma-Knife radiosurgery of choroidal melanomas

Background/aimsTo report on conservation of visual acuity after Gamma-Knife radiosurgery of choroidal melanoma.MethodsA total of 189 patients with choroidal melanoma were treated with Gamma-Knife stereotactic single-fraction radiosurgery at a single...

Cone Beam CT (CBCT) Evaluation of Inter- and Intra-Fraction Motion for Patients Undergoing Brain Radiotherapy Immobilized using a Commercial Thermoplastic Mask on a Robotic Couch

Patients receiving fractionated intensity-modulated radiation therapy (IMRT) for brain tumors are often immobilized with a thermoplastic mask; however, masks do not perfectly re-orient the patient due to factors including the maximum pressure which can be applied to the face, deformations of the mask assembly, patient compliance, etc. Consequently, ~3-5mm PTV margins (beyond the CTV) are often recommended. We aimed to determine if smaller PTV margins are feasible using mask immobilization coupled with 1) a gantry mounted CBCT image guidance system and 2) position corrections provided by a full six-degree of freedom (6-DOF) robotic couch. A cohort of 34 brain tumor patients was treated with fractionated IMRT. After the mask set-up, an initial CBCT was obtained and registered to the planning CT. The robotic couch corrected the misalignments in all 6-DOF and a pre-treatment verification CBCT was then obtained. The results indicated a repositioning alignment within our threshold of 1.5 mm (3D). Treatment was subsequently delivered. A post-treatment CBCT was obtained to quantify intra-fraction motion. Initial, pre-treatment and post-treatment CBCT image data was analyzed. A total of 505 radiation fractions were delivered to the 34 patients resulting in ~1800 CBCT scans. The initial median 3D (magnitude) set-up positioning error was 2.60 mm. Robotic couch corrections reduced the 3D median error to 0.53 mm prior to treatment. Intra-fraction movement was responsible for increasing the median 3D positioning error to 0.86 mm, with 8% of fractions having a 3D positioning error greater than 2 mm. Clearly CBCT image guidance coupled with a robotic 6-DOF couch dramatically improved the positioning accuracy for patients immobilized in a thermoplastic mask system; however, such intra-fraction motion would be too large for single fraction radiosurgery.

Cone Beam Computed Tomography Image Guidance System for a Dedicated Intracranial Radiosurgery Treatment Unit

Image guidance has improved the precision of fractionated radiation treatment delivery on linear accelerators. Precise radiation delivery is particularly critical when high doses are delivered to complex shapes with steep dose gradients near critical structures, as is the case for intracranial radiosurgery. To reduce potential geometric uncertainties, a cone beam computed tomography (CT) image guidance system was developed in-house to generate high-resolution images of the head at the time of treatment, using a dedicated radiosurgery unit. The performance and initial clinical use of this imaging system are described. A kilovoltage cone beam CT system was integrated with a Leksell Gamma Knife Perfexion radiosurgery unit. The X-ray tube and flat-panel detector are mounted on a translational arm, which is parked above the treatment unit when not in use. Upon descent, a rotational axis provides 210° of rotation for cone beam CT scans. Mechanical integrity of the system was evaluated over a 6-month period. Subsequent clinical commissioning included end-to-end testing of targeting performance and subjective image quality performance in phantoms. The system has been used to image 2 patients, 1 of whom received single-fraction radiosurgery and 1 who received 3 fractions, using a relocatable head frame. Images of phantoms demonstrated soft tissue contrast visibility and submillimeter spatial resolution. A contrast difference of 35 HU was easily detected at a calibration dose of 1.2 cGy (center of head phantom). The shape of the mechanical flex vs scan angle was highly reproducible and exhibited <0.2 mm peak-to-peak variation. With a 0.5-mm voxel pitch, the maximum targeting error was 0.4 mm. Images of 2 patients were analyzed offline and submillimeter agreement was confirmed with conventional frame. A cone beam CT image guidance system was successfully adapted to a radiosurgery unit. The system is capable of producing high-resolution images of bone and soft tissue. The system is in clinical use and provides excellent image guidance without invasive frames.

Therapeutic profile of single-fraction radiosurgery of vestibular schwannoma: unrelated malignancy predicts tumor control

Radiosurgery has become an accepted treatment option for vestibular schwannomas. Nevertheless, predictors of tumor control and treatment toxicity in current radiosurgery of vestibular schwannomas are not well understood. To generate new information on predictors of tumor control and cranial nerve toxicity of single-fraction radiosurgery of vestibular schwannomas, we conducted a single-institution long-term observational study of radiosurgery for sporadic vestibular schwannomas. Minimum follow-up was 3 years. Investigated as potential predictors of tumor control and cranial nerve toxicity were treatment technology; tumor resection preceding radiosurgery; tumor size; gender; patient age; history of cancer, vascular disease, or metabolic disease; tumor volume; radiosurgical prescription dose; and isodose line. Three hundred eighty-six patients met inclusion criteria. Treatment failure was observed in 27 patients. History of unrelated cancer (strongest predictor) and prescription dose significantly predicted tumor control. The cumulative incidence of treatment failure was 30% after 6.5 years in patients with unrelated malignancy and 10% after ≥15 years in patients without such cancer (P < .02). Tumor volume was the only predictor of trigeminal neuropathy (observed in 6 patients). No predictor of facial nerve toxicity was found. On the House and Brackmann scale, 1 patient had a permanent one-level drop and 7 a transient drop of 1 to 3 levels. Serviceable hearing was preserved in 75.1%. Tumor hearing before radiosurgery, recurrence, and prescription isodose predicted ototoxicity. Unrelated malignancy is a strong predictor of tumor control. Tumor recurrence predominantly predicts ototoxicity. These findings potentially will aid future clinical decision making in ambiguous cases.

Single-fraction Radiosurgery for Presumed Intracranial Meningiomas: Efficacy and Complications From a 22-Year Experience

To define the rate of tumor control and factors associated with radiation-related complications after single-fraction radiosurgery (SRS) for patients with imaging defined intracranial meningiomas. Retrospective review of 251 patients (192 women, 59 men) having SRS for imaging-defined intracranial meningiomas between 1990 and 2008. Excluded were patients with radiation-induced tumors, meningiomatosis, or neurofibromatosis. The mean patient age was 58.6 ± 13.4 years. The majority of tumors involved the skull base/tentorium (n = 210, 83.7%). The mean treatment volume was 7.7 ± 6.2 cm(3); the mean tumor margin dose was 15.8 ± 2.0 Gy. Follow-up (mean, 62.9 ± 43.9 months) was censored at last evaluation (n = 224), death (n = 22), or tumor resection (n = 5). No patient died from tumor progression or radiation-related complications. Tumor size decreased in 181 patients (72.1%) and was unchanged in 67 patients (26.7%). Three patients (1.2%) had in-field tumor progression noted at 28, 145, and 150 months, respectively. No patient had a marginal tumor progression. The 3- and 10-year local control rate was 99.4%. One patient had distant tumor progression at 105 months and underwent repeat SRS. Thirty-one patients (12.4%) had either temporary (n = 8, 3.2%) or permanent (n = 23, 9.2%) symptomatic radiation-related complications including cranial nerve deficits (n = 14), headaches (n = 5), hemiparesis (n = 5), new/worsened seizure (n = 4), cyst-formation (n = 1), hemifacial spasm (n = 1), and stroke (n = 1). The 1- and 5-year complication rates were 8.3% and 11.5%, respectively. Radiation-related complications were associated with convexity/falx tumors (HR = 2.8, 95% CI 1.3-6.1, p = 0.009) and increasing tumor volume (HR = 1.05, 95% CI 1.0-1.1, p = 0.04) on multivariate analysis. No patient developed a radiation-induced tumor. Single-fraction SRS at the used dose range provides a high rate of tumor control for patients with imaging defined intracranial meningiomas. However, treatment failures were noted after 10 years emphasizing the need for long-term imaging follow-up after meningioma SRS.

Spinal Cord Tolerance to Reirradiation With Single-Fraction Radiosurgery: A Swine Model

This study was performed to determine swine spinal cord tolerance to single-fraction, partial-volume irradiation 1 year after receiving uniform irradiation to 30 Gy in 10 fractions. A 10-cm length of spinal cord (C3-T1) was uniformly irradiated to 30 Gy in 10 consecutive fractions and reirradiated 1 year later with a single radiosurgery dose centered within the previously irradiated segment. Radiosurgery was delivered to a cylindrical volume approximately 5 cm in length and 2 cm in diameter, which was positioned laterally to the cervical spinal cord, resulting in a dose distribution with the 90%, 50%, and 10% isodose lines traversing the ipsilateral, central, and contralateral spinal cord, respectively. Twenty-three pigs were stratified into six dose groups with mean maximum spinal cord doses of 14.9 ± 0.1 Gy (n = 2), 17.1 ± 0.3 Gy (n = 3), 19.0 ± 0.1 Gy (n = 5), 21.2 ± 0.1 Gy (n = 5), 23.4 ± 0.2 Gy (n = 5), and 25.4 ± 0.4 Gy (n = 3). The mean percentage of spinal cord volumes receiving ≥10 Gy for the same groups were 34% ± 1%, 40% ± 1%, 46% ± 3%, 52% ± 1%, 56 ± 3%, and 57% ± 1%. The study endpoint was motor neurologic deficit as determined by a change in gait during a 1- year follow-up period. A steep dose-response curve was observed with a 50% incidence of paralysis (ED(50)) for the maximum point dose of 19.7 Gy (95% confidence interval, 17.4-21.4). With two exceptions, histology was unremarkable in animals with normal neurologic status, while all animals with motor deficits showed some degree of demyelination and focal white matter necrosis on the irradiated side, with relative sparing of gray matter. Histologic comparison with a companion study of de novo irradiated animals revealed that retreatment responders had more extensive tissue damage, including infarction of gray matter, only at prescription doses >20 Gy. Pigs receiving spinal radiosurgery 1 year after receiving 30 Gy in 10 fractions were not at significantly higher risk of developing motor deficits than pigs that received radiosurgery alone.

Single-Fraction Radiosurgery for Presumed Intracranial Meningiomas: Efficacy and Complications from a 22-Year Experience

Single-Fraction Radiosurgery for Presumed Intracranial Meningiomas: Efficacy and Complications from a 22-Year Experience

Lateral Dose-volume Effects in Single-fraction Radiosurgery of the Cervical Spinal Cord: A Swine Model

Lateral Dose-volume Effects in Single-fraction Radiosurgery of the Cervical Spinal Cord: A Swine Model

Single-fraction radiosurgery for the treatment of renal tumors in singular renal units.

e15168 Background: High-dose local radiation treatment (stereotactic radiosurgery, or SRS) was added for selected patients to improve local control and overall survival. We report on toxicity and local tumor control in patients with renal tumors who were treated with aggressive local irradiation using a single fraction SRS with the Cyberknife in singular renal units to avoid nephrectomy and consecutive hemodialysis. Methods: N=28 patients with renal tumors and an eastern cooperative oncology group (ECOG) status of 0 or 1 were treated with SRS. Patients with surgically removable renal lesions were not included. Prior to SRS gold markers were planted into the renal parenchyma under ultrasonographic guidance. Results: N=11 patients had transitional carcinoma of the renal pelvis and n=17 had renal cell carcinoma. No skin toxicity occurred after SRS, and SRS did not induce other side effects. Local tumor control 9 months after SRS was 98% (95% CI: 89-99%). There were no treatment related deaths, and late complications after SRS were not noted so far. Renal function remained stable with a median creatinine at baseline 1,5 mg/dl and 1,53 mg/dl after six months. None of the patients developed metastases during a median follow-up of 12 months. Dialysis and surgery were avoided in all patients. Conclusions: SRS for selected patients with renal tumors in singular renal units is safe and effective and maybe an alternative to surgery and consecutive hemodialysis. Single-fraction delivery as an outpatient procedure allows for convenient integration of SRS into various oncological treatment concepts. Further studies are needed to determine the limits of SRS in this setting.

Single-fraction radiosurgery for the treatment of renal tumors in singular renal units.

368 Background: High-dose local radiation treatment (stereotactic radiosurgery [SRS]) was added for selected patients to improve local control and overall survival in metastases. We report on toxicity and local tumor control in patients with renal tumors who were treated with aggressive local irradiation using a single fraction SRS with the Cyberknife in singular renal units to avoid hemodialysis. Methods: n=18 patients with renal tumors and an eastern cooperative oncology group (ECOG) status of 0 or 1 were treated with SRS. Patients with surgically removable renal lesions were not included. Prior to SRS gold markers were planted into the renal parenchyma under ultrasonographic guidance. Results: Nine patients had transitional carcinoma of the renal pelvis, six patients had renal cell carcinoma and three had other tumor entities. No skin toxicity occurred after SRS, and SRS did not induce other side effects. Local tumor control 9 months after SRS was 98% (95% CI: 89-99%). There were no treatment related deaths, and late complications after SRS were not noted so far. Renal function so far remained stable without a change in serum creatinine. Conclusions: SRS for selected patients with renal tumors is safe and effective. Single-fraction delivery as an outpatient procedure allows for convenient integration of SRS into various oncological treatment concepts. Further studies are needed to determine the limits of SRS in this setting. No significant financial relationships to disclose.

Single fraction radiosurgery using Rapid Arc for treatment of intracranial targets

BackgroundStereotactic-Radio-Surgery (SRS) using Conformal-Arc-Therapy (CAT) is a well established irradiation technique for treatment of intracranial targets. Although small safety margins are required because of very high accuracy of patient positioning and exact online localisation, there are still disadvantages like long treatment time, high number of monitor units (MU) and covering of noncircular targets. This planning study analysed whether Rapid Arc (RA) with stereotactic localisation for single-fraction SRS can solve these problems.MethodsTen consecutive patients were treated with Linac-based SRS. Eight patients had one or more brain metastases. The other patients presented a symptomatic vestibularis schwannoma and an atypic meningeoma. For all patients, two plans (CAT/RA) were calculated and analysed.ResultsConformity was higher for RA with additional larger low-dose areas. Furthermore, RA reduced the number of MU and the treatment time for all patients. Dose to organs at risk were equal or slightly higher using RA in comparison to CAT.ConclusionsRA provides a new alternative for single-fraction SRS irradiation combining advantages of short treatment time with lower number of MU and better conformity in addition to accuracy of stereotactic localisation in selected cases with uncomplicated clinical realization.

Local disease control after decompressive surgery and adjuvant high-dose single-fraction radiosurgery for spine metastases

OBJECT Adjuvant radiation following epidural spinal cord decompression for tumor is a powerful tool used to achieve local disease control and preserve neurological function. To the authors' knowledge, only 1 published report addresses adjuvant stereotactic radiosurgery after this procedure, but that study used significantly lower doses than are currently prescribed. The authors review their experience using high-dose single-fraction radiosurgery as a postoperative adjuvant following surgical decompression and instrumentation to assess long-term local tumor control, morbidity, and survival. METHODS A retrospective chart review identified 21 patients treated with surgical decompression and instrumentation for high-grade, epidural, spinal cord compression from tumor, followed by single-fraction high-dose spinal radiosurgery (dose range 18-24 Gy, median 24 Gy). Spinal cord dose was limited to a cord maximal dose of 14 Gy. Tumor histologies, time between surgery and radiosurgery, time to local recurrence after radiosurgery as assessed by serial MR imaging, and time to death were determined. Competing risk analysis was used to evaluate these end points. RESULTS In this series, 20 tumors treated (95%) were considered highly radioresistant to conventional external beam radiation. The planning target volume received a high dose (24 Gy) in 16 patients (76.2%), and a low dose (18 or 21 Gy) in 5 patients (23.8%). During the study, 15 (72%) of 21 patients died, and in all cases death was due to systemic progression as opposed to local failure. The median overall survival after radiosurgery was 310 days (range 37 days to not reached). One patient (4.8%) underwent repeat surgery for local failure and 2 patients (9.5%) underwent spine surgery for other reasons. Local control was maintained after radiosurgery in 17 (81%) of 21 patients until death or most recent follow-up, with an estimated 1-year local failure risk of 9.5%. Of the failures, 3 of 4 were noted in patients receiving low-dose radiosurgery, equaling an overall failure rate of 60% (3 of 5 patients) and a 1-year local failure estimated risk of 20%. Those patients receiving adjuvant stereotactic radiosurgery with a high dose had a 93.8% overall local control rate (15 of 16 patients), with a 1-year estimated failure risk of 6.3%. Competing risk analysis showed this to be a significant difference between radiosurgical doses. One patient experienced a significant radiation-related complication; there were no wound-related issues after radiosurgery. CONCLUSIONS Spine radiosurgery after surgical decompression and instrumentation for tumor is a safe and effective technique that can achieve local tumor control until death in the vast majority of patients. In this series, those patients who received a higher radiosurgical dose had a significantly better local control rate.

Single-fraction radiosurgery for treatment of spinal and cerebral metastases from renal cell carcinoma under systemic tyrosine kinase inhibition.

4625 Background: Angiogenic therapy shows promising treatment effects in patients with metastatic renal cell carcinoma (RCC). Limited response has been documented for metastatic lesions in the brain and spine. High-dose local radiation treatment (stereotactic radiosurgery, or SRS) was added for selected patients to improve local control and overall survival. We report on toxicity and local tumor control in patients with metastatic renal cell carcinoma who were simultaneously treated with angiogenic therapy and aggressive local irradiation. Methods: 88 patients with spinal (n=47) or cerebral (n=41) metastatic lesions from RCC and an eastern cooperative oncology group (ECOG) status of 0 or 1 were treated systemically with sorafenib or sunitinib and additional SRS. Patients with surgically removable cerebral lesions were not included. Dose was not withheld or delayed while patients were simultaneously treated with SRS. Results: Median time from initial diagnosis to metastatic spread was 0.6 years (range 0 - 3.5 years). Median follow-up was 14.7 months (range 1-42 months). Twenty-seven patients were treated with sunitinb (50 mg pod, 4 weeks on 2 weeks off) and 61 patients were treated with sorafenib (400 mg bid). One patient suffered a tumor hemorrhage after SRS that did not require treatment. No skin toxicity occurred after SRS, and SRS did not alter the side effect profile of systemic angiogenic therapy. Neither neurotoxicity nor myelopathy was observed. Local tumor control 15 months after SRS was 98% (95% CI: 89-99%). The median pain score on the visual analogue scale before spinal treatment was 5 (range 1-8). After SRS the median pain score was significantly lowered to 0 (range 0-2, p<0.001). There were no treatment related deaths, and late complications after SRS were not noted so far. Conclusions: Systemic angiogenic therapy and SRS for selected RCC patients with cerebral and spinal metastases is safe and effective. Single-fraction delivery as an outpatient procedure allows for convenient integration of SRS into various oncological treatment concepts. Further studies are needed to determine the limits of SRS for RCC metastases outside the brain and spine. No significant financial relationships to disclose.

Overall and progression-free survival and visual and endocrine outcomes for patients with parasellar lesions treated with intensity-modulated stereotactic radiosurgery

Linear accelerator single-fraction radiosurgery (SRS) for skull base lesions is usually delivered with dynamic conformal arcs (DCAs), but intensity-modulated radiosurgery (IMRS) is another option when SRS dose is limited by proximity of the optic nerve and chiasm. We review the long-term outcome of patients treated with IMRS for parasellar lesions. Fourteen patients with parasellar lesions were treated with IMRS when standard DCA radiosurgery was limited by optic nerve tolerance. Prospective patient data included endocrine function, visual acuity and field testing, nonoptic nerve cranial neuropathy, and overall survival. In addition, tumor control on serial magnetic resonance imaging is reported as progression-free survival (PFS). Six patients with cavernous sinus meningiomas and eight with recurrent pituitary adenomas were treated. Three of the pituitary tumors were hormonally active (two with Cushing disease, one with acromegaly). The median patient age was 50 years (range 24-70 years). Median follow-up was 54 months. Average tumor treatment volume was 4.99 ml (average dose 16 Gy, average of 10 IMRS fields). Tumor control was achieved in 11 of 14 (79%) patients. Median PFS has not been reached in our patient population. Thirteen patients are alive (one died of an unrelated cancer). No patients developed new endocrinological, ophthalmological, or cranial nerve deficits. IMRS allows for treatment of parasellar lesions when standard DCA SRS is limited by optic nerve tolerance. Although our follow-up period was relatively short and the number of patients was small, it appears that this can be accomplished with a high tumor control rate and survival without new endocrinopathies, optic neuropathies, or other complications in patients who have failed other therapies.

Radiation Dose–Volume Effects in the Brain

We have reviewed the published data regarding radiotherapy (RT)-induced brain injury. Radiation necrosis appears a median of 1-2 years after RT; however, cognitive decline develops over many years. The incidence and severity is dose and volume dependent and can also be increased by chemotherapy, age, diabetes, and spatial factors. For fractionated RT with a fraction size of <2.5 Gy, an incidence of radiation necrosis of 5% and 10% is predicted to occur at a biologically effective dose of 120 Gy (range, 100-140) and 150 Gy (range, 140-170), respectively. For twice-daily fractionation, a steep increase in toxicity appears to occur when the biologically effective dose is >80 Gy. For large fraction sizes (>or=2.5 Gy), the incidence and severity of toxicity is unpredictable. For single fraction radiosurgery, a clear correlation has been demonstrated between the target size and the risk of adverse events. Substantial variation among different centers' reported outcomes have prevented us from making toxicity-risk predictions. Cognitive dysfunction in children is largely seen for whole brain doses of >or=18 Gy. No substantial evidence has shown that RT induces irreversible cognitive decline in adults within 4 years of RT.

Radiation Dose–Volume Effects of Optic Nerves and Chiasm

Publications relating radiation toxicity of the optic nerves and chiasm to quantitative dose and dose-volume measures were reviewed. Few studies have adequate data for dose-volume outcome modeling. The risk of toxicity increased markedly at doses >60 Gy at approximately 1.8 Gy/fraction and at >12 Gy for single-fraction radiosurgery. The evidence is strong that radiation tolerance is increased with a reduction in the dose per fraction. Models of threshold tolerance were examined.

Laparoscopic Renal Cryoablation: 8-Year, Single Surgeon Outcomes

We present 5 to 11-year (median 8) oncological outcomes after laparoscopic renal cryoablation. Between September 1997 and October 2008 we performed renal cryoablation in 340 patients, of whom 80 treated laparoscopically by a single surgeon before October 2003 had a minimum 5-year followup. Followup involved magnetic resonance imaging on postoperative day 1, at 3, 6 and 12 months, and annually thereafter. Cryolesion biopsy was performed at 6 months. All data were prospectively accrued. In the 80 patients with minimum 5-year followup mean age was 66 years, mean tumor size was 2.3 cm (range 0.9 to 5.0), median American Society of Anesthesiologists score was 3 and mean body mass index was 28 kg/m(2). Five patients had local recurrence, 2 had locoregional recurrence with metastasis and 4 had distant metastasis without locoregional recurrence. Six patients died of cancer. In the 55 patients with biopsy proven renal cell cancer at a median followup of 93 months (range 60 to 132) 5-year overall, disease specific and disease-free survival rates were 84%, 92% and 81%, and 10-year rates were 51%, 83% and 78%, respectively. On multivariate analysis previous radical nephrectomy for RCC was the only significant predictor of disease-free and disease specific survival (p = 0.023 and 0.030, respectively). Laparoscopic renal cryoablation is effective oncological treatment for a renal mass in select patients. A disease specific survival rate of 92% at 5 years and 83% at 10 years is possible. Preceding radical nephrectomy for renal cell carcinoma was the only independent factor predicting disease-free and disease specific survival.