Postobliteration Arteriovenous Malformation Mimicking Malignant Change 30 Years After X-Knife Treatment-Case Report and Review of Literature.

BACKGROUND: Arteriovenous malformations (AVMs) are potentially dangerous vascular anomalies of the brain that can cause seizures or intracranial hemorrhage in patients if left untreated. Because full excision of these lesions is not always possible in deep or eloquent areas of the brain, radiosurgical advances have gone a long way in the control and treatment of AVMs. Postradiosurgery AVMs are followed closely via outpatient clinics with serial imaging every few months to assess AVM obliteration. Post X-knife treatment AVMs still carry with them some risk of rebleeding and even a chance of malignant transformation. CASE DESCRIPTION: In this article, we report a case of a post X-knife-treated arteriovenous malformation with the appearance of malignant change on magnetic resonance imaging and thallium-201 on follow-up 30 years after treatment. Imaging with magnetic resonance angiography showed obliteration of the lesion but progressive change in size with new soft tissue components, which suggests radiation-related secondary malignancy. CONCLUSIONS: Surgery was arranged, and pathology results indicate no malignant change.

Dosimetric comparison of helical tomotherapy and conventional Linac-based X-knife stereotactic body radiation therapy for primary lung cancer or pulmonary metastases.

BACKGROUND: To compare helical tomotherapy (HT) with X-knife stereotactic body radiation therapy (HT-SBRT/X-SBRT) for primary or metastatic lung cancer regarding planning target volume (PTV) coverage, such as homogeneity index (HI), conformity index (CI) and dose-volume histogram (DVH) of organs at risk (OARs). METHODS: We retrospectively analyzed 21 patients receiving definitive radiation treatment for non-small cell lung cancer (NSCLC) or pulmonary metastases at our institution between March 2015 and October 2016. Tumors were irradiated with 4-10 Gy per fraction in 5-15 fractions. Plans were compared according to PTV coverage and OARs sparing. RESULTS: Significant differences between HT and X-knife were observed for both HI (P=0.003) and CI (P<0.001). The V5 (P=0.001), V10 (P=0.009), V20 (P=0.001), the mean lung dose (P=0.005) of total lung and maximum dose of the spinal cord (P=0.010) were significantly lower in the X-SBRT group than the HT-SBRT group. There were no significant differences for the V30 (P=0.075) and the mean heart dose (P=0.584) between the two groups. CONCLUSIONS: X-SBRT was dosimetrically superior to HT-SBRT, when applied in these tumors' maximum diameters <5 cm. As HT resulted in increased low-dose volume, it is essential to optimize the patient selection in order to avoid severe radiation pneumonitis in HT-SBRT.

Evaluation on efficacy and safety of the addition of X-knife therapy to gefitinib in NSCLC patients with symptomatic brain metastases.

BACKGROUND: Stereotactic radiosurgery (SRS) is a widely used therapy for brain metastases(BMs) in Non-small cell lung cancer(NSCLC). However, its role in symptomatic patients with EGFR mutation remains unclear. We have retrospectively reviewed the clinical data of patients with symptomatic BMs whom received SRS as a salvage approach and concurrent gifitinib therapy. METHODS: Seven patients with primary NSCLC, symptomatic BMs, and EGFR mutation were identified in a retrospective review of patients treated with SRS using X-knife at Guangdong 999 Brain Hospital between 1 January 2012 and 31 August 2014. The median follow-up of these patients was 16 months. Image fusion technique was used to determine cumulative doses to targeted lesions, whole brain, and critical brain structures. Toxicities and complications were identified by clinical records. RESULTS: SRS(X-knife) was selected to be performed on seven patients (two males and five females) diagnosed with NSCLC and EGFR mutation due to the presence of encephaledema, compression of ventricles, or other complications. Neurological symptoms (such as paresis, aphasia, sensory and visual disturbances) were not present in any patients before or after SRS treatment, and the postoperative Karnofsky performance status(KPS) was improved in all patients. Median overall survival(OS) was 16 months and median progression free survival(PFS) was 10 months. CONCLUSIONS: The improvement of KPS and survival were reliable by SRS(X-knife) with concurrent gifitinib therapy in NSCLC patients with symptomatic BMs, and EGFR mutation. Given the small sample size, further prospective studies with a greater number of patients are warranted to confirm our results.

Iridium-Knife: Another knife in radiation oncology.

PURPOSE: Intratarget dose escalation with superior conformity is a defining feature of three-dimensional (3D) iridium-192 (192Ir) high-dose-rate (HDR) brachytherapy (BRT). In this study, we analyzed the dosimetric characteristics of interstitial 192Ir HDR BRT for intrathoracic and cerebral malignancies. We examined the dose gradient sharpness of HDR BRT compared with that of linear accelerator-based stereotactic radiosurgery and stereotactic body radiation therapy, usually called X-Knife, to demonstrate that it may as well be called a Knife. METHODS AND MATERIALS: Treatment plans for 10 patients with recurrent glioblastoma multiforme or intrathoracic malignancies, five of each entity, treated with X-Knife (stereotactic radiosurgery for glioblastoma multiforme and stereotactic body radiation therapy for intrathoracic malignancies) were replanned for simulated HDR BRT. For 3D BRT planning, we used identical structure sets and dose prescription as for the X-Knife planning. The indices for qualitative treatment plan analysis encompassed planning target volume coverage, conformity, dose falloff gradient, and the maximum dose-volume limits to different organs at risk. RESULTS: Volume coverage in HDR plans was comparable to that calculated for X-Knife plans with no statistically significant difference in terms of conformity. The dose falloff gradient-sharpness-of the HDR plans was considerably steeper compared with the X-Knife plans. CONCLUSIONS: Both 3D 192Ir HDR BRT and X-Knife are effective means for intratarget dose escalation with HDR BRT achieving at least equal conformity and a steeper dose falloff at the target volume margin. In this sense, it can reasonably be argued that 3D 192Ir HDR BRT deserves also to be called a Knife, namely Iridium-Knife.

The clinical outcome of intracranial hemangioblastomas treated with linac-based stereotactic radiosurgery and radiotherapy.

Recent publications have reported stereotactic radiosurgery as an effective and safe treatment for intracranial hemangioblastomas. However, because of the low incidence of these particular tumors, reports on large patient number studies have not yet been available. The objective of this study was to analyze the clinical results of 14 patients with 56 intracranial hemangioblastomas treated with linear accelerator (linac)-based stereotactic radiosurgery (SRS) and radiotherapy (SRT) in the same institute. The median age of patients was 41 years (range, 28-73 years). Nine of the patients (64%) had von Hippel-Lindau disease. A total of 39 lesions (70%) were treated with CyberKnife (CK), and 17 lesions (30%) were treated with X-Knife. The median pretreatment volume was 0.26 cm(3) (range, 0.026-20.4 cm(3)). The median marginal dose was 20 Gy (range, 10-32 Gy) in 1 fraction (range, 1-10 fractions). The median follow-up time was 24 months (range, 11-89 months). At the last follow-up, 47 tumors (84%) were stable, 7 (13%) decreased and 2 (4%) increased. The 1-, 2- and 6-year local control rates were 98%, 88% and 73%, respectively. No radiation complications were observed in this study. There was a trend toward local failure only in cystic tumors, but this trend was not found to be statistically significant. SRS/SRT achieved a high local control rate in intracranial hemangioblastomas without radiation-induced complications.

Dosimetric comparison of linear accelerator-based stereotactic radiosurgery systems.

Stereotactic radiosurgery (SRS) is a special radiotherapy technique used to irradiate intracranial lesions by 3-D arrangements of narrow photon beams eliminating the needs of invasive surgery. Three different tertiary collimators, namely BrainLab and Radionics circular cones and BrainLab micro multileaf collimator (mMLC), are used for linear accelerator-based SRS systems (X-Knife). Output factor (S(t)), tissue maximum ratio (TMR) and off axis ratio (OAR) of these three SRS systems were measured using CC01 (Scanditronix/ Welhofer) and Pinpoint (PTW) cylindrical and Markus plane parallel ionization chambers as well as TLD and radiochromic film. Measurement results of CC01 and Pinpoint chambers were very close to each other which indicate that further reduction in volume and physical dimensions of cylindrical ionization chamber is not necessary for SRS/SRT dosimetry. Output factors of BrainLab and Radionics SRS cones were very close to each other while output factors of equivalent diameter mMLC field were different from SRS circular cones. TMR of the three SRS systems compared were very close to one another. OAR of Radionics cone and BrainLab mMLC were very close to each other, within 2%. However, OARs of BrainLab cone were found comparable to OARs of Radionics cone and BrainLab mMLC within maximum variation of 4%. In addition, user-measured similar data of other three mMLC X-Knives were compared with the mMLC X-Knife data measured in this work and found comparable. The concept of switching over to mMLC-based SRS/SRT is thus validated from dosimetric characteristics as well.