Megumi Uto

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.

Geometric and dosimetric quality assurance using logfiles and a 3D helical diode detector for Dynamic WaveArc

PURPOSE To conduct patient-specific geometric and dosimetric quality assurance (QA) for the Dynamic WaveArc (DWA) using logfiles and ArcCHECK (Sun Nuclear Inc., Melbourne, FL, USA). METHODS Twenty DWA plans, 10 for pituitary adenoma and 10 for prostate cancer, were created using RayStation version 4.7 (RaySearch Laboratories, Stockholm, Sweden). Root mean square errors (RMSEs) between the actual and planned values in the logfiles were evaluated. Next, the dose distributions were reconstructed based on the logfiles. The differences between dose-volumetric parameters in the reconstructed plans and those in the original plans were calculated. Finally, dose distributions were assessed using ArcCHECK. In addition, the reconstructed dose distributions were compared with planned ones. RESULTS The means of RMSEs for the gantry, O-ring, MLC position, and MU for all plans were 0.2°, 0.1°, 0.1 mm, and 0.4 MU, respectively. Absolute means of the change in PTV D99% were 0.4 ± 0.4% and 0.1 ± 0.1% points between the original and reconstructed plans for pituitary adenoma and prostate cancer, respectively. The mean of the gamma passing rate (3%/3 mm) between the measured and planned dose distributions was 97.7%. In addition, that between the reconstructed and planned dose distributions was 99.6%. CONCLUSIONS We have demonstrated that the geometric accuracy and gamma passing rates were within AAPM 119 and 142 criteria during DWA. Dose differences in the dose-volumetric parameters using the logfile-based dose reconstruction method were also clinically acceptable in DWA.

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

Radiation-induced cystic brain necrosis developing 10 years after linac-based stereotactic radiosurgery for brain metastasis

Abstract Cystic brain necrosis (CBN) is a rare form of BN. It typically occurs as a very late complication, and no standard treatment has been established. We report a case of a 59-year-old man who developed CBN 10 years after radiation therapy for metastatic brain tumors. The therapy consisted of whole brain radiotherapy followed by linac-based stereotactic radiosurgery as a boost. Initially, the CBN continued to expand despite treatment with corticosteroids and bevacizumab. Therefore, we resected the tumor and implanted an Ommaya reservoir, which successfully stabilized the lesion. Although the prognosis of patients with brain metastases is generally poor, some patients, like the one reported here, achieve long survival. Therefore, we should follow such cases carefully, considering the possibility of developing CBN as a late complication.