Kengo Ogura

Efficacy of salvage stereotactic radiotherapy for recurrent glioma: impact of tumor morphology and method of target delineation on local control

In this study, we assessed the efficacy of salvage stereotactic radiotherapy (SRT) for recurrent glioma. From August 2008 to December 2012, 30 patients with recurrent glioma underwent salvage SRT. The initial histological diagnoses were World Health Organization (WHO) grades II, III, and IV in 6, 9, and 15 patients, respectively. Morphologically, the type of recurrence was classified as diffuse or other. Two methods of clinical target delineation were used: A, a contrast‐enhancing tumor; or B, a contrast‐enhancing tumor with a 3–10‐mm margin and/or surrounding fluid attenuation inversion recovery (FLAIR) high‐intensity areas. The prescribed dose was 22.5–35 Gy delivered in five fractions at an isocenter using a dynamic conformal arc technique. The overall survival (OS) and local control probability (LCP) after SRT were calculated using the Kaplan–Meier method. A univariate analysis was used to test the effect of clinical variables on OS/LCP. The median follow‐up period was 272 days after SRT. The OS and LCP were 83% and 56% at 6 months after SRT, respectively. Morphologically, the tumor type correlated significantly with both OS and LCP (P = 0.006 and <0.001, respectively). The method of target delineation also had a significant influence on LCP (P = 0.016). Grade 3 radiation necrosis was observed in two patients according to Common Terminology Criteria for Adverse Events, version 3. Salvage SRT was safe and effective for recurrent glioma, especially non‐diffuse recurrences. Improved local control might be obtained by adding a margin to contrast‐enhancing tumors or including increased FLAIR high‐intensity areas.

Volumetric modulated Dynamic WaveArc therapy reduces the dose to the hippocampus in patients with pituitary adenomas and craniopharyngiomas

PURPOSE Reducing the radiation dose to the hippocampus is important to preserve cognitive function in patients with brain tumors. The Vero4DRT system can realize a new irradiation technique, termed volumetric-modulated Dynamic WaveArc therapy (VMDWAT), which allows the safe use of sequential noncoplanar volumetric-modulated beams without couch rotation. Because VMDWAT appears to reduce the hippocampal dose in patients with pituitary adenomas and craniopharyngiomas, we performed a planning study to compare the dose distribution of volumetric-modulated arc therapy using only a coplanar arc (coVMAT) and VMDWAT. METHODS AND MATERIALS CoVMAT and VMDWAT plans were created for 30 patients with pituitary adenomas and craniopharyngiomas. The prescription dose was 52.2 Gy in 29 fractions, with 99% of each planning target volume covered by 90% of the prescribed dose. Optimization was performed for maximal reduction of the dose to the hippocampus. Treatment time was defined as the beam-on time. RESULTS The mean equivalent dose in 2 Gy fractions to 40% of the volume of the bilateral hippocampus (EQD40%) for coVMAT/VMDWAT were 9.90/5.31 Gy, respectively (P < .001). The mean EQD40% in VMDWAT was less than 7.3 Gy, which is the threshold for predicting cognitive impairment. Although the volume of normal brain receiving 5 Gy (V5) was significantly larger in VMDWAT, compared with coVMAT, the normal brain volume receiving 10, 15, 20, 25, 30, 35, 40, 45, and 50 Gy (V10-50) was significantly smaller in VMDWAT. The conformity and homogeneity indices were significantly better in VMDWAT. The mean VMDWAT treatment time was longer compared with coVMAT (70.1 vs 67.1 seconds, respectively). CONCLUSIONS Although VMDWAT increased brain V5 and the treatment time compared with coVMAT, it significantly reduced the dose to the hippocampus and brain V10 to V50 and improved target conformity and homogeneity. VMDWAT could be a promising treatment technique for pituitary adenomas and craniopharyngiomas.

Dosimetric advantages of O-ring design radiotherapy system for skull-base tumors

The purpose of this study was to investigate whether a new O‐ring design radiotherapy delivery system has advantages in radiotherapy planning for skull‐base tumors. Twenty‐five patients with skull‐base tumors were included in this study. Two plans were made using conventional (Plan A) or new (Plan B) techniques. Plan A consisted of four dynamic conformal arcs (DCAs): two were horizontal, and the other two were from cranial directions. Plan B was created by converting horizontal arcs to those from caudal directions making use of the O‐ring design radiotherapy system. The micromultileaf collimators were fitted to cover at least 99% of the planning target volume with prescribed doses, 90% of the dose at the isocenter. The two plans were compared in terms of target homogeneity, conformity, and irradiated volume of normal tissues, using a two‐sided paired t‐test. For evaluation regarding target coverage, the homogeneity indices defined by the International Commission on Radiation Units and Measurements 83 were 0.099±0.010 (mean ± standard deviation) and 0.092±0.010, the conformity indices defined by the Radiation Therapy Oncology Group were 1.720±0.249 and 1.675±0.239, and the Paddicks conformity indices were 0.585±0.078 and 0.602±0.080, in Plans A and B, respectively. For evaluation of irradiated normal tissue, the Paddicks gradient indices were 3.118±0.283 and 2.938±0.263 in Plans A and B, respectively. All of these differences were statistically significant (p‐values <0.05). The mean doses of optic nerves, eyes, brainstem, and hippocampi were also significantly lower in Plan B. The DCA technique from caudal directions using the new O‐ring design radiotherapy system can improve target homogeneity and conformity compared with conventional DCA techniques, and can also decrease the volume of surrounding normal tissues that receives moderate doses. PACS numbers: 87.55.‐x, 87.55.D‐, 87.55.dk

Whole brain radiotherapy with volumetric‐modulated arc therapy for pediatric intracranial embryonic carcinoma prevents permanent alopecia

Excellent survival outcomes for nongerminomatous germ cell tumors (NGGCT), including embryonic carcinoma, have been achieved with the recent advances in platinum-based multidrug chemotherapy with craniospinal irradiation (CSI) and boost irradiation for the primary tumor.1–3 However, such intensive chemoradiotherapy occasionally causes severe, although not life-threatening, late adverse events including permanent alopecia.4,5 Permanent alopecia could negatively affect self-image and self-esteem, leading to a decrease in social interactions.6 Whole brain irradiation with volumetric-modulated arc therapy (WBI-VMAT) can reduce thedose tohair follicles, and is alreadyapplied in adult patients to limit the extent of alopecia.7 Whether WBI-VMAT can prevent permanent alopecia in pediatric patients has not yet been reported. Herein, we report a 9-year-old female who presented to our hospital with a 1-month history of headache. Progressive polydipsia and polyuria were also found, which suggested diabetes insipidus. Cranialmagnetic resonance imaging (MRI) showedagadolinium-enhanced mass in the suprasellar region. The examination of cerebrospinal fluid was negative for malignant cells and whole spine MRI did not indicate any dissemination. Laboratory tests showed elevation of serum alpha-fetoprotein (AFP; 49.8 ng/ml) and human chorionic gonadotropin (HCG)-β (8.8 mIU/ml). The patient was diagnosed with embryonal carcinoma based on histology of the biopsied tumor tissue. The patient received five courses of chemotherapy consisting of cyclophosphamide, cisplatin, and etoposide. Following the first course of chemotherapy, the patient obtained a complete response with normalization of serumAFP andHCG-β levels. Considering the high rate of local and spinal recurrence,1 the patient was given CSI of 35.2 Gy in 22 fractions followed by boost irradiation to theprimary tumorof 17Gy in10 fractions. The fourth course of chemotherapy and the radiotherapy were started concurrently. The treatment plan for CSI consisted of irradiation to the spinal cord andWBI-VMAT. In theWBI-VMATplan, the skin structurewas defined as a 5 mm-thick region beneath the surface of the skin. Optimization was performed to set doses to the skin as low as possible while maintaining a homogenous dose distribution to the target. As a result, the mean dose to the skin structure was less than 21 Gy (Fig. 1A). The patient received chemoradiotherapy without any serious treatmentrelated complications.Hair regrowthwasfirst observed2months after

Volumetric-modulated arc therapy vs conventional fixed-field intensity-modulated radiotherapy in a whole-ventricular irradiation: A planning comparison study.

This study evaluated the dosimetric difference between volumetric-modulated arc therapy (VMAT) and conventional fixed-field intensity-modulated radiotherapy (cIMRT) in whole-ventricular irradiation. Computed tomography simulation data for 13 patients were acquired to create plans for VMAT and cIMRT. In both plans, the same median dose (100% = 24 Gy) was prescribed to the planning target volume (PTV), which comprised a tumor bed and whole ventricles. During optimization, doses to the normal brain and body were reduced, provided that the dose constraints of the target coverage were satisfied. The dose-volume indices of the PTV, normal brain, and body as well as monitor units were compared between the 2 techniques by using paired t-tests. The results showed no significant difference in the homogeneity index (0.064 vs 0.065; p = 0.824) of the PTV and conformation number (0.78 vs 0.77; p = 0.065) between the 2 techniques. In the normal brain and body, the dose-volume indices showed no significant difference between the 2 techniques, except for an increase in the volume receiving a low dose in VMAT; the absolute volume of the normal brain and body receiving 1 Gy of radiation significantly increased in VMAT by 1.6% and 8.3%, respectively, compared with that in cIMRT (1044 vs 1028 mL for the normal brain and 3079.2 vs 2823.3 mL for the body; p<0.001). The number of monitor units to deliver a 2.0-Gy fraction was significantly reduced in VMAT compared with that in cIMRT (354 vs 873, respectively; p<0.001). In conclusion, VMAT delivers IMRT to complex target volumes such as whole ventricles with fewer monitor units, while maintaining target coverage and conformal isodose distribution comparable to cIMRT; however, in addition to those characteristics, the fact that the volume of the normal brain and body receiving a low dose would increase in VMAT should be considered.