CyberKnife® radiosurgery in the treatment of complex skull base tumors: analysis of treatment planning parameters

Homogeneity Index (HI) is an objective tool to analyz the uniformity of dose distribution in the target volume. Various formulae have been described in literature for its calculation but there is paucity of data regarding the ideal formula and the factors affecting this index. This study was undertaken to analyze HI in our patients using various formulae and to find out the co-relation between HI and prescribed dose, target volume and target location. A retrospective review of 99 patients was performed. HI was calculated using five different formulae (A-E). The patients were divided in five groups each, based on prescribed dose, target volume and target location and mean HI of each group was analysed to find the co-relation between these factors and HI. When there were multiple target volumes the primary target volume was studied. The statistical calculation was done using SPSS version 16.0. Ninety nine patients were found evaluable with 75 males and 24 females. Ninety five patients were treated with radical intent and four with palliative intent. The sites treated were head and neck (46.4%), Pelvis (17.1%), brain (15.1%), abdomen (12.1%), and thorax (6.1%). The mean prescribed dose was 4304 cGy (centiGray) and the mean target volume was 476.2 cc. The mean value of HI was 1.21, 2.08, 30.13, 21.51 and 1.27 with different formulae. There was considerable agreement between HI calculated using various formulae specially the formulae considering prescribed dose (C, D). On statistical analysis, there was no significant co-relation between the location and volume of target but there was a trend toward better HI with increasing prescribed dose. Future studies with more number of patients can confirm our results.

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“…But treatment planning parameters like homogeneity index can be assessed much earlier to guide the quality of a plan. [12]…”

Section: Discussionmentioning

confidence: 99%

Homogeneity Index: An objective tool for assessment of conformal radiation treatments

Kataria¹,

Sharma²,

Subramani³

et al. 2012

J Med Phys

281

201

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“…The majority of the tumors (54%) were Koos Grade 2. The conformity index (prescribed isodose volume/tumor volume encompassed by the prescription isodose line) and the modified conformity index [(prescribed isodose volume / tumor volume encompassed by the prescription isodose line)/tumor volume] was calculated on all patients (Collins et al, 2006). The median conformality index was 1.60 with a range of 1.01–2.59 while the median prescription isodose line was 80% with a range from 60 to 92%.…”

Section: Methodsmentioning

confidence: 99%

Frameless Fractionated Stereotactic Radiosurgery for Vestibular Schwannomas: A Single-Institution Experience

Karam¹,

Tai²,

Strohl³

et al. 2013

Front. Oncol.

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Objective: To examine tumor control, hearing preservation, and complication rates after frameless fractionated stereotactic radiosurgery (SRS) in patients with vestibular schwannomas (VS).Methods: Thirty-seven patients treated with fractionated SRS from 2002 to 2011 were retrospectively analyzed. Ninety-five percent were treated with 25 Gy in five fractions, targeting a median tumor volume of 1.03 cc (range 0.14–7.60).Results: With a median follow-up of 4.25 years (range, 15 months–9 years), no tumors required an additional treatment resulting in 100% tumor control rate. Radiographic control rate was 91% in 32 patients at a median follow-up of 3 years. Of the 14 patients with serviceable hearing and with audiograms, the hearing preservation rate was 78% at a median follow-up of 18 months. Twenty-six patients with serviceable hearing pretreatment, were evaluated by a phone survey with a hearing preservation rate of 73% at a 5 year median follow-up. There were two cases that developed both new increased trigeminal parasthesias and facial spasms but there were no cases of facial weakness. Patient had 96% of good to excellent satisfaction rate with the treatment at a median follow-up of 5 years.Conclusion: Frameless fractionated SRS treatment of VS results in good rate of tumor control. Hearing preservation rate and rates of cranial nerve toxicity are comparable to what is reported in the literature. Patients choose this modality because of its non-invasive nature and are generally very satisfied with their long term outcome.

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“…To the best of our knowledge this is the first reported case of CSF leakage caused by CyberKnife ® therapy, although a few cases of post-radiation CSF leakage were reported in gamma-knife treatment for skull base tumors [8-10]. There is no doubt that CyberKnife ® treatment is very effective for skull base tumors; [2-4] however, the risk of radiation-induced CSF leakage should be considered when tumor invasion of the dura is suspected. Emergency surgical repair is required if CSF leakage is identified to avoid severe meningitis, because CSF leakage cannot be cured by palliative treatments.…”

Section: Discussionmentioning

confidence: 99%

“…Fractionated CyberKnife ® radiation delivers a highly conformational dose distribution to the complex shapes of tumor extensions into the skull base [1]. It is clear that many patients with skull base tumors have benefited from this radiosurgery [2-4]. Here we present a case of skull base osteosarcoma which, remarkably, was shrunk by CyberKnife ® radiation, but cerebrospinal fluid (CSF) leakage occurred due to the tumor shrinkage.…”

Section: Introductionmentioning

confidence: 99%

Skull base osteosarcoma presenting with cerebrospinal fluid leakage after CyberKnife® treatment: a case report

et al. 2013

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IntroductionCyberKnife® radiation is an effective treatment for unresectable skull base tumors because it can deliver a highly conformational dose distribution to the complex shapes of tumor extensions. There have been few reports of severe complications with this treatment. This is the first published case report to our knowledge of cerebrospinal fluid leakage induced by CyberKnife® radiotherapy.Case presentationA skull base tumor was identified on magnetic resonance imaging in a 78-year-old Asian woman with a headache in her forehead. An endoscopic transnasal tumor resection was performed; however, the tumor, invading into the cavernous sinuses and optic canal, was not completely removed. During the subtotal resection of the tumor, no cerebrospinal fluid leakage was observed. Osteosarcoma was histologically diagnosed, and CyberKnife® radiation was performed to the residual tumor considering the aggressive feature of the tumor with a molecular immunology Borstel-1 index of 15%. Five months after the treatment, magnetic resonance imaging showed definite tumor shrinkage, and the patient had been living her daily life without any troubles. After another month, the patient was transferred to our clinic because of coma with high fever, and computed tomography demonstrated severe pneumocephalus. Rhinorrhea was definitely identified on admission; therefore, emergency repair of the cerebrospinal fluid leakage was performed using an endoscope. Dural defects at the bottom of the sella turcica were identified under careful endoscopic observation and fat tissue was patched to the dural defects. Follow-up computed tomography proved complete disappearance of air from the cisterns 2 weeks after the surgery, and the patient was discharged from our hospital without any neurological deficits.ConclusionCyberKnife® radiation is one of the effective treatments for skull base tumors; however, the risk of cerebrospinal fluid leakage should be considered when tumor invasion to the dura mater is suspected. Emergency surgical treatment is required when cerebrospinal fluid leakage is induced by the radiotherapy because the leakage is not expected to be healed by palliative treatments.

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CyberKnife® radiosurgery in the treatment of complex skull base tumors: analysis of treatment planning parameters

Cited by 56 publications

References 32 publications

Homogeneity Index: An objective tool for assessment of conformal radiation treatments

Homogeneity Index: An objective tool for assessment of conformal radiation treatments

Frameless Fractionated Stereotactic Radiosurgery for Vestibular Schwannomas: A Single-Institution Experience

Skull base osteosarcoma presenting with cerebrospinal fluid leakage after CyberKnife® treatment: a case report

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