Tsuyoshi Onoe

Four-Dimensional Measurement of the Displacement of Internal Fiducial Markers During 320-Multislice Computed Tomography Scanning of Thoracic Esophageal Cancer

PURPOSE To investigate the three-dimensional movement of internal fiducial markers placed near esophageal cancers using 320-multislice CT. METHODS AND MATERIALS This study examined 22 metal markers in the esophageal wall near the primary tumors of 12 patients treated with external-beam photon radiotherapy. Motion assessment was analyzed in 41 respiratory phases during 20 s of cine CT in the radiotherapy position. RESULTS Motion in the cranial-caudal (CC) direction showed a strong correlation (R(2) > 0.4) with the respiratory curve in most markers (73%). The average absolute amplitude of the marker movement was 1.5 ± 1.6 mm, 1.6 ± 1.7 mm, and 3.3 ± 3.3 mm in the left-right (LR), anterior-posterior (AP), and CC directions, respectively. The average marker displacements in the CC direction between peak exhalation and inhalation for the 22 clips were 1.1 mm (maximum, 5.5 mm), 3.0 mm (14.5 mm), and 5.1 mm (16.3 mm) for the upper, middle, and lower thoracic esophagus, respectively. CONCLUSIONS Motion in primary esophagus tumor was evaluated with 320-multislice CT. According to this study, 4.3 mm CC, 1.5 mm AP, and 2.0 mm LR in the upper, 7.4 mm CC, 3.0 mm AP, and 2.4 mm LR in the middle, and 13.8 mm CC, 6.6 mm AP, and 6.8 mm LR in the lower thoracic esophagus provided coverage of tumor motion in 95% of the cases in our study population.

Cost-effectiveness analysis of cochlear dose reduction by proton beam therapy for medulloblastoma in childhood

Background: The aim of this study is to evaluate the cost-effectiveness of proton beam therapy with cochlear dose reduction compared with conventional X-ray radiotherapy for medulloblastoma in childhood. Methods: We developed a Markov model to describe health states of 6-year-old children with medulloblastoma after treatment with proton or X-ray radiotherapy. The risks of hearing loss were calculated on cochlear dose for each treatment. Three types of health-related quality of life (HRQOL) of EQ-5D, HUI3 and SF-6D were used for estimation of quality-adjusted life years (QALYs). The incremental cost-effectiveness ratio (ICER) for proton beam therapy compared with X-ray radiotherapy was calculated for each HRQOL. Sensitivity analyses were performed to model uncertainty in these parameters. Results: The ICER for EQ-5D, HUI3 and SF-6D were

Contrast media-assisted visualization of brain metastases by kilovoltage cone-beam CT

21 716/QALY,

High-dose-rate interstitial brachytherapy for gynecologic malignancies—dosimetric changes during treatment period

11 773/QALY, and

Reirradiation of spinal metastases with intensity-modulated radiation therapy: an analysis of 23 patients

20 150/QALY, respectively. One-way sensitivity analyses found that the results were sensitive to discount rate, the risk of hearing loss after proton therapy, and costs of proton irradiation. Cost-effectiveness acceptability curve analysis revealed a 99% probability of proton therapy being cost effective at a societal willingness-to-pay value. Conclusions: Proton beam therapy with cochlear dose reduction improves health outcomes at a cost that is within the acceptable cost-effectiveness range from the payers standpoint.

4D digitally reconstructed radiography for verifying a lung tumor position during volumetric modulated arc therapy

The latest linear accelerator equipped with a kilovoltage (kV) cone-beam CT (CBCT) unit is useful for registration at the time of treatment, and thus reduces the setup error [1 4]. But in the case of intracranial or abdominal tumors, the contours of the tumors are difficult to determine on the CT images without contrast media, since such tumors are located next to normal soft tissue whose Hounsfield unit is close to those of the tumors themselves. Image registration by CBCT is performed based on the bony structures or soft tissue around the tumor. But this process does not necessarily guarantee that the position of the isocenter at treatment is identical with that at the time of planning CT, since bone or soft-tissue registration is based on a volume-matching process. It is difficult to know the exact tumor location for a low-contrast tumor even if on-board registration of the tumor is intended, since the tumor contour is not well visualized even on planning CT images without contrast media. We attempted to visualize metastatic brain

Survival benefit of adding docetaxel, cisplatin, and 5-fluorouracil induction chemotherapy to concurrent chemoradiotherapy for locally advanced nasopharyngeal carcinoma with nodal Stage N2–3

To overcome cranio-caudal needle displacement in pelvic high-dose-rate interstitial brachytherapy (HDRIB), we have been utilizing a fullystretched elastic tape to thrust the template into the perineum. The purpose of the current study was to evaluate dosimetric changes during the treatment period using this thrusting method, and to explore reproducible planning methods based on the results of the dosimetric changes. Twenty-nine patients with gynecologic malignancies were treated with HDRIB at the Cancer Institute Hospital. Pre-treatment and post-treatment computed tomography (CT) scans were acquired and a virtual plan for post-treatment CT was produced by applying the dwell positions/times of the original plan. For the post-treatment plan, D90 for the clinical target volume (CTV) and D2cc for the rectum and bladder were assessed and compared with that for the original plan. Cranio-caudal needle displacement relative to CTV during treatment period was only 0.7 ± 1.9 mm. The mean D90 values for the CTV in the pre- and post-treatment plans were stable (6.8 Gy vs. 6.8 Gy) and the post-treatment/pre-treatment D90 ratio was 1.00 ± 0.08. The post-/pre-treatment D2cc ratio was 1.14 ± 0.22 and the mean D2cc for the rectum increased for the post-treatment plan (5.4 Gy vs. 6.1 Gy), especially when parametrial infiltration was present. The mean D2cc for the bladder was stable (6.3 Gy vs. 6.6 Gy) and the ratio was 1.06 ± 0.20. Our thrusting method achieved a stable D90 for the CTV, in contrast to previous prostate HDRIB reports displaying reductions of 35–40% for D90 during the treatment period.

SU-E-J-183: Dose Distribution Generated from 131 I Radionuclide Using SPECT-CT

This study aimed to evaluate the efficacy and safety of reirradiation with intensity-modulated radiation therapy (IMRT) for spinal metastases. We retrospectively analyzed 23 patients with spinal metastases who underwent IMRT reirradiation between December 2006 and July 2013. We evaluated the spinal radiation doses during the first and second radiation therapy courses, the interval between the courses, and the clinical outcomes after reirradiation, including skeletal-related events, local control rates (LCRs), overall survival (OS), and toxicities. The median time from the first irradiation to reirradiation was 13 months (range, 2–75 months). The median reirradiation dose delivered to 90% of the planning target volume was 24.5 Gy in 5 fractions (range, 14.7–50 Gy in 3–25 fractions). Nineteen patients experienced pain at reirradiation, and 15 of these attained pain relief. Two of the three patients with paresis in the upper or lower extremities upon initiation of reirradiation demonstrated improvement. Local progression was identified in four patients. The median time to local progression was 37 months. The 1- and 2-year LCRs after reirradiation were 88% and 75%, respectively. The 1- and 2-year OS rates after reirradiation were 45% and 20%, respectively, with a median OS of 12 months. No late toxicities occurred. In conclusion, spinal metastasis reirradiation using IMRT appears safe; pain relief and paresis improvement and/or prevention can be expected, along with a reduced risk of radiation-induced toxicity, especially in the spinal cord.

SU‐E‐T‐530: Projection Image Correction for 4D VMAT‐CT

We have proposed four dimensional (4D) digitally reconstructed radiography (DRR) for verifying a lung tumor position during volumetric modulated arc therapy (VMAT). An internal target volume (ITV) was defined based on two clinical target volumes (CTVs) delineated on maximum exhalation and maximum inhalation images acquired by 4D planning computed tomography (CT). A planning target volume (PTV) was defined by adding a margin of 5 mm to the ITV on the maximum exhalation 3D CT images. A single-arc VMAT plan was created on the same CT data using Pinnacle SmartArc with a maximum multi-leaf collimator leaf speed of 1 mm/degree, thereby resulting in quasi-conformal field shapes while optimizing each beam intensity for each gantry angle. During VMAT delivery, cone-beam CT (CBCT) projection data were acquired by an on-board kilovoltage X-ray unit and a flat panel 2D detector. Four CBCT image sets with different respiratory phases were reconstructed using in-house software, where respiratory phases were extracted from the projection data. Subsequently a CTV was delineated on each of the 4D CBCT images by an oncologist. Using the resulting 4D CBCT data including the CTV contours, 4D DRRs during the VMAT delivery were calculated as a function of gantry angle. It was confirmed that the contoured CTV was within the radiation field during the four-fraction lung VMAT delivery. The proposed 4D DRR may facilitate the verification of the position of a respiratory moving lung tumor during VMAT delivery on each treatment day.

Single-Arc Volumetric Modulated Arc Therapy Planning for Left Breast Cancer and Regional Nodes

Background Concurrent chemoradiotherapy followed by adjuvant chemotherapy (CCRT-AC) has been established as the standard of care in locally advanced nasopharyngeal carcinoma (LA-NPC). The survival benefit of induction chemotherapy (ICT) for LA-NPC remains controversial. We analyzed the efficacy and feasibility of docetaxel, cisplatin and 5-fluorouracil (TPF) ICT followed by CCRT for LA-NPC with nodal Stage N2-3. Methods We performed a retrospective analysis of 28 LA-NPC patients with nodal Stage N2-3 receiving induction TPF followed by CCRT (TPF group; n = 12) or CCRT-AC (CCRT group; n = 16) between October 2006 and May 2016. Results The median follow-up periods were 36.4 (range 6.7-55.2) and 40.1 months (range 4.3-99.0) for the TPF and CCRT groups, respectively. One- and three-year overall survival for the TPF group vs. the CCRT group were 100% and 100% vs. 94% and 75%, respectively (P = 0.21). The cumulative one- and three-year incidences of locoregional recurrence or progression for the TPF group vs. the CCRT group were 10% and 21% vs. 16% and 32% (P = 0.49), and those of distant metastasis were 0% and 0% vs. 26% and 26%, respectively (P = 0.08). The common Grade 3-4 acute toxicities were neutropenia, anorexia, febrile neutropenia, and stomatitis in the TPF group. The Grade 3-4 late toxicities did not differ significantly between the two groups. Conclusions This study suggests that induction TPF followed by CCRT might reduce distant metastasis, so this combination may be feasible for the treatment of LA-NPC with nodal Stage N2-3.