Verification of Low Risk for Perihippocampal Recurrence in Patients with Brain Metastases Who Received Whole-Brain Radiotherapy with Hippocampal Avoidance / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The purpose of this study was to analyze the patterns of failure and survival outcome in patients with brain metastases who received whole-brain radiotherapy (WBRT) with hippocampal avoidance (HA) using simultaneous integrated boost (SIB) on metastatic brain tumors. MATERIALS AND METHODS: We retrospectively reviewed 42 patients treated with HA-WBRT for brain metastases. A total of 25 Gy for whole brain and 35-55 Gy for gross tumors were delivered with 10 fractionations. Local tumor and intracranial progression were defined as a recurrence or tumor progression in SIB field and any recurrence or tumor progression within whole brain, respectively. Progression in HA zone was defined as the recurrence within the area expanded 5 mm from HA zone. RESULTS: Median follow-up duration was 10.0 months (range, 4.1 to 56.4 months). Intracranial progression was observed in 13 patients (31.0%) and the median duration from the start of HA-WBRT to progression was 10.6 months (range, 0.9 to 33.0 months). Local tumor progression and new metastasis outside SIB field occurred in 10 patients (23.8%) and nine patients (21.4%), respectively. There was no isolated hippocampal metastasis, except only one patient (2.4%) with multiple metastases inside and outside HA zone simultaneously. Median survival time and intracranial progression-free survival rate at 1 year were 19.4 months (95% confidence interval [CI], 9.6 to 29.2) and 71.5%, respectively, and those for overall survival were 26.5 months (95% CI, 15.4 to 37.5) and 67.9%, respectively. CONCLUSION: HA-WBRT was associated with low risk of new metastasis in HA region in the patients with brain metastases. These findings would serve as useful guidance on applying HA-WBRT in clinical practice.

Setup Error and Effectiveness of Weekly Image-Guided Radiation Therapy of TomoDirect for Early Breast Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: This study investigated setup error and effectiveness of weekly image-guided radiotherapy (IGRT) of TomoDirect for early breast cancer. MATERIALS AND METHODS: One hundred and fifty-one breasts of 147 consecutive patients who underwent breast conserving surgery followed by whole breast irradiation using TomoDirect in 2012 and 2013 were evaluated. All patients received weekly IGRT. The weekly setup errors from simulation to each treatment in reference to chest wall and surgical clips were measured. Random, systemic, and 3-dimensional setup errors were assessed. Extensive setup error was defined as 5 mm above the margin in any directions. RESULTS: All mean errors were within 3 mm of all directions. The mean angle of gantry shifts was 0.6degrees. The mean value of absolute 3-dimensional setup error was 4.67 mm. In multivariate analysis, breast size (odds ratio, 2.82; 95% confidence interval, 1.00 to 7.90) was a significant factor for extensive error. The largest significant deviation of setup error was observed in the first week of radiotherapy (p < 0.001) and the deviations gradually decreased with time. The deviation of setup error was 5.68 mm in the first week and within 5 mm after the second week. CONCLUSION: In this study, there was a significant association between breast size and significant setup error in breast cancer patients who received TomoDirect. The largest deviation occurred in the first week of treatment. Therefore, patients with large breasts should be closely observed on every fraction and fastidious attention is required in the first fraction of IGRT.

Tumor bed volumetric changes during breast irradiation for the patients with breast cancer

PURPOSE: The aim of this study was to evaluate changes in breast tumor bed volume during whole breast irradiation (WBI). MATERIALS AND METHODS: From September 2011 to November 2012, thirty patients who underwent breast-conserving surgery (BCS) followed by WBI using computed tomography (CT) simulation were enrolled. Simulation CT scans were performed before WBI (CT1) and five weeks after the breast irradiation (CT2). The tumor bed was contoured based on surgical clips, seroma, and postoperative change. We retrospectively analyzed the factors associated with tumor bed volumetric change. RESULTS: The median tumor bed volume on CT1 and CT2 was 29.72 and 28.6 mL, respectively. The tumor bed volume increased in 9 of 30 patients (30%) and decreased in 21 of 30 patients (70%). The median percent change in tumor bed volume between initial and boost CT was -5%. Seroma status (p = 0.010) was a significant factor in tumor bed volume reduction of 5% or greater. However, patient age, body mass index, palpability, T stage, axillary lymph node dissection, and tumor location were not significant factors for tumor bed volumetric change. CONCLUSION: In this study, volumetric change of tumor bed cavity was frequent. Patients with seroma after BCS had a significant volume reduction of 5% or greater in tumor bed during breast irradiation. Thus, resimulation using CT is indicated for exquisite boost treatment in breast cancer patients with seroma after surgery.

Verification of Skin Dose in Tomotherapy Using the Developed Phantom for Image Based Radiation Treatment System / 의학물리

Radiation treatment for skin cancer has recently increased in tomotherapy. It was reported that required dose could be delivered with homogeneous dose distribution to the target without field matching using electron and photon beam. Therapeutic beam of tomotherapy, however, has several different physical characteristic and irradiation of helical beam is involved in the mechanically dynamic factors. Thus verification of skin dose is requisite using independent tools with additional verification method. Modified phantom for dose measurement was developed and skin dose verification was performed using inserted thermoluminescent dosimeters (TLDs) and GafChromic EBT films. As the homogeneous dose was delivered to the region including surface and 6 mm depth, measured dose using films showed about average 2% lower dose than calculated one in treatment planning system. Region indicating about 14% higher and lower absorbed dose was verified on measured dose distribution. Uniformity of dose distribution on films decreased as compared with that of calculated results. Dose variation affected by inhomogeneous material, Teflon, little showed. In regard to the measured dose and its distribution in tomotherapy, verification of skin dose through measurement is required before the radiation treatment for the target located at the curved surface or superficial depth.

Development of QA Phantom Prototype for Imaged Based Radiation Treatment System / 의학물리

In this study, we developed the protopype of QA phantom for image QA including an additional component for image based radiation treatment system. The new phantom considered two main parts: Image quality and fusion accuracy. Image quality part included for daily CT number linearity and spatial resolution, and fusion accuracy part designed to simulate a simple translation-rotation setting. The CT scans of the phantom obtained from conventional CT, MVCT of Tomotherapy unit, and both image sets were satisfied the recommendation of spatial resolution. This phantom was simple and efficient for daily imaging QA, and it is important to provide a new concept of verification of image registration.