With the increasing use of flattening filter free (FFF) beams, it is important to evaluate the impact on the skin dose and target coverage of breast cancer treatments. This study aimed to compare skin doses of treatments using FFF and flattening filter (FF) beams for breast cancer. The study established treatment plans for left breast of an anthropomorphic phantom using Halcyon's 6-MV FFF beam and TrueBeam's 6-MV FF beam. Volumetric modulated arc therapy (VMAT) with varying numbers of arcs and intensity modulated radiation therapy (IMRT) were employed, and skin doses were measured at five points using Gafchromic EBT3 film. Each measurement was repeated three times, and averaged to reduce uncertainty. All plans were compared in terms of plan quality to ensure homogeneous target coverage. The study found that when using VMAT with two, four, and six arcs, in-field doses were 19%, 15%, and 6% higher, respectively, when using Halcyon compared to TrueBeam. Additionally, when using two arcs for VMAT, in-field doses were 10% and 15% higher compared to four and six arcs when using Halcyon. Finally, in-field dose from Halcyon using IMRT was about 1% higher than when using TrueBeam. Our research confirmed that when treating breast cancer with FFF beams, skin dose is higher than with traditional FF beams. Moreover, number of arcs used in VMAT treatment with FFF beams affects skin dose to the patient. To maintain a skin dose similar to that of FF beams when using Halcyon, it may be worth considering increasing the number of arcs.

Purpose: An optimal once-daily radiotherapy (RT) regimen is under investigation for definitive concurrent chemoradiotherapy (CCRT) in limited disease small cell lung cancer (LD-SCLC). We compared the efficacy and safety of dose escalation with intensity-modulated radiotherapy (IMRT).Materials and Methods: Between January 2016 and March 2021, patients treated with definitive CCRT for LD-SCLC with IMRT were retrospectively reviewed. Patients who received a total dose <50 Gy or those with a history of thoracic RT or surgery were excluded. The patients were divided into two groups (standard and dose-escalated) based on the total biologically effective dose (BED, α/β = 10) of 70 Gy. The chemotherapeutic regimen comprised four cycles of etoposide and cisplatin.Results: One hundred and twenty-two patients were analyzed and the median follow-up was 27.8 months (range, 4.4 to 76.9 months). The median age of the patients was 63 years (range, 35 to 78 years) and the majority had a history of smoking (86.0%). The 1- and 3-year overall survival rates of the escalated dose group were significantly higher than those of the standard group (93.5% and 50.5% vs. 76.7% and 33.3%, respectively; p = 0.008), as were the 1- and 3-year freedom from in-field failure rates (91.4% and 66.5% vs. 73.8% and 46.9%, respectively; p = 0.018). The incidence of grade 2 or higher acute and late pneumonitis was not significantly different between the two groups (p = 0.062, 0.185). Conclusion: Dose-escalated once-daily CCRT with IMRT led to improved locoregional control and survival, with no increase in toxicity.

The purpose of this study is to investigate the effects of the dose distributions caused by a low-strength magnetic field transverse to the incident photon beams in inhomogeneous medium of the body such as the lung. A simple water-air-water phantom was used to evaluate the magnetic field induced dose effect by the field size of the beam and the beam energy. The Gafchromic BET3 self-developing dosimetry film was utilized for all measurements. Our results indicated that a localized magnetic field within the air region offers the capability of producing dose enhancement and dose reduction regions between the proximal and distal interfaces. It was demonstrated that the magnitude of the dose perturbation depends not only on the beam energy, but also on the field size of the beam. It is expected that this magnet technology could be further developed to provide higher dose to the tumor and lower dose to the normal tissue in radiation therapy for lung cancer.

BackgroundSystemic inflammation plays a critical role in cancer progression and oncologic outcomes in cancer patients. We investigated whether preoperative inflammatory biomarkers, including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and neutrophil to lymphocyte ratio (NLR), could be surrogate biomarkers for predicting overall survival (OS) in soft tissue sarcoma (STS) patients treated with surgery and postoperative radiotherapy.MethodsA series of 99 patients who presented with localized extremity STS were retrospectively reviewed. The preoperative CRP levels, ESR, and NLR were evaluated for associations with OS, disease-free survival (DFS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS). Cutoff values for CRP, ESR, and NLR were derived from receiver-operating characteristic curve analysis.ResultsElevated CRP (>0.14mg/dL), ESR (>15mm/h), and NLR (>1.95) levels were seen in 33, 44, and 45 patients, respectively. Of these three inflammatory biomarkers, elevated CRP and ESR were associated with a poorer OS (CRP: P=0.050; ESR: P=0.001), DFS (CRP: P=0.023; ESR: P=0.003), and DMFS (CRP: P=0.015; ESR: P=0.001). By multivariate analysis, an elevated ESR was found to be an independent prognostic factor for OS (HR 3.580, P=0.025) and DMFS (HR 3.850, P=0.036) after adjustment for other established prognostic factors.ConclusionsThe preoperative ESR level is a simple and useful surrogate biomarker for predicting survival outcomes in STS patients and might improve the identification of high-risk patients of tumor relapse in clinical practice.

Background: To evaluate the role of radiotherapy (RT) as an adjuvant or definitive treatment in primary tracheal adenoid cystic carcinoma (ACC) for local tumor control and survival. Methods: A retrospective chart review was performed in 22 patients treated with adjuvant or definitive RT for primary tracheal ACC at a single center between November 1994 and December 2008. Results: Thirteen and 9 patients received adjuvant and definitive RT, respectively. Microscopic residual disease after surgery was pathologically reported in 11 patients. The median RT dose was 59.4 Gy for adjuvant and 74.4 Gy for definitive RT. The overall response rate for definitive RT was 77.8%. Six patients in the definitive RT group exhibited local progression (LP), whereas 14 patients in both groups exhibited distant metastasis. The most common recurrence site in cases of treatment failure was the lung parenchyma. The median follow-up duration was 123 months, and the 10-year overall survival (OS) rate was 54.2%. Although LP was the most common cause of death (4 patients), two-thirds of the patients treated with definitive RT lived for > 5 years. The 5-year and 10-year LP-free survival (LPFS) rates in the definitive RT group were 66.7 and 26.7%, respectively. Patients with higher RT dose by brachytherapy boost had good 5-year OS, 83.3%, and showed no local progression till 5-years. Most of the RT-induced side-effects were mild and tolerable, but 2 patients died of tracheal stenosis without any tumor recurrence. Conclusions: Adjuvant RT may be suitable for controlling microscopic residual disease, whereas definitive RT may yield appropriate long-term survival in > 50% patients with unresectable tracheal ACC. Dose escalation should be considered to warrant long-term survival in definitive RT.

PURPOSE:The concentration of capecitabine peaks at 1-2 hours after administration. We therefore assumed that proper timing of capecitabine administration and radiotherapy would maximize radiosensitization and influence survival among patients with locally advanced rectal cancer.MATERIALS AND METHODS:We retrospectively reviewed 223 patients with locally advanced rectal cancer who underwent preoperative chemoradiation, followed by surgery from January 2002 to May 2006. All patients underwent pelvic radiotherapy (50 Gy/25 fractions) and received capecitabine twice daily at 12-hour intervals (1,650 mg/m2/day). Patients were divided into two groups according to the time interval between capecitabine intake and radiotherapy. Patients who took capecitabine 1 hour before radiotherapy were classified as Group A (n = 109); all others were classified as Group B (n = 114).RESULTS:The median follow-up period was 72 months (range, 7 to 149 months). Although Group A had a significantly higher rate of good responses (44% vs. 25%; p = 0.005), the 5-year local recurrence-free survival rates of 93% in Group A and 97% in Group B did not differ significantly (p = 0.519). The 5-year disease-free survival and overall survival rates were also comparable between the groups.CONCLUSIONS:Despite the better pathological response in Group A, the time interval between capecitabine and radiotherapy administration did not have a significant effect on survivals. Further evaluations are needed to clarify the interaction of these treatment modalities.

The purpose of this study was to present an improved method of dose modulation over the increase of build-up for existing 6MV photon beam. Two neodymium permanent magnets with a strength of 0.5 T (Tesla) were applied with a magnetic field perpendicular to the photon beam. The effects of dose on build-up region with or without the magnetic field were measured according to the magnet-to- magnet distance (MMS) and the magnet-to-surface distance (MSD). For MMS = 6 cm and MSD = 2.5 cm, D-0mm, D-2 mm, D-5 (mm), and D-10 (mm) showed improved doses of 6.8 %, 14.6 %, 6.9 %, and 2.1 %, respectively, as compared with 6MV open beam. In this study, the device with low strength magnetic field can be applied directly to the outside of the human body when the target volume located close to the skin is delivered with radiation. It is expected that the method of build-up modulation using a low strength magnetic field will be feasible in the clinical applications.

INTRODUCTION:The purpose of this study was to assess the effect of dose escalation of stereotactic ablative radiotherapy (SABR) by investigating the long-term clinical outcomes of SABR for stage I non-small-cell lung cancer (NSCLC). METHODS:A retrospective analysis was performed on a total of 169 patients with 178 lesions of stage I NSCLC treated with SABR at a single institution from June 2000 to May 2015. The standard dose scheme for SABR was 48 Gy in 4 fractions during the early period of the analysis, but it was escalated to 60 Gy in 4 fractions from June 2009. All failures were recorded over the follow-up period. RESULTS:Median follow-up time was 32 months. The 5-year overall survival rate was 46.7%, and the actuarial local control rate was 79.3%. Tumor size was an independent prognostic factor for survival. No relapse occurred in tumors ≤ 2 cm irrespective of SABR dose. Escalated doses of approximately 60 Gy in 4 fractions (biologically effective dose [BED] = 150 Gy10) achieved higher local control compared with 48 Gy in 4 fractions (BED = 106 Gy10) (76.2% vs. 60.6%) at 5-year follow-up (P = .022) in tumors > 2 cm. There were no differences in treatment-related toxicities between the dose groups. Major failures consisted of distant metastasis to another lung parenchyma. CONCLUSION:SABR provides satisfactory long-term local control and high overall survival in medically inoperable stage I NSCLC. Tumors ≤ 2 cm had no local recurrence regardless of dose; whereas for tumors > 2 cm, an escalated BED of approximately 150 Gy10 provided significantly higher local tumor control.

The purpose of this study is to propose the use of a beam spoiler for improving the build-up region of photon beam by using external magnetic field with a low strength of 0.5 T (Tesla) outside the human body. A homemade magnet device which can apply a transverse magnetic field to photon beam was developed. The effect of dose enhancement on build-up region was investigated by the beam spoiler-to-magnet distance (BMD), the magnet-to-magnet distance (MMD), and the magnet-to-surface distance (MSD). Build-up regions of 6 MV photon beam with and without the magnetic field were measured for the field size to 5 x 5 cm(2). When applying the low magnetic field with MMD of 10 cm, D-0mm, D-2mm, D-5mm and D-10mm at BSD of 13 cm and MSD of 5 cm were increased by approximately 3.2 %, 3.9 %, 1.7 % and 0.4 %, respectively, compared to the build-up of the existing 6 MV photon beam without the magnetic field. The dose reduction was 5.1 % compared to skin dose for 4 MV photon beam without the magnetic field. It is expected that use of a beam spoiler in the magnet device designed in this study could provide improved dose distributions in build-up regions while maintain similar surface dose to the existing 6 MV photon beam without the magnetic field.

The purpose of this study is to determine the optimal target configurations to improve the uniformity of dose distribution for the electronic brachytherapy source. A truncated conical-shaped transmission type was designed. Monte Carlo simulation technique was used to investigate the target thickness, geometry of electron beam, and target angle of a truncated conical-shaped target for the electronic brachytherapy X-ray source. Dosimetric parameters recommended by TG-43U1 protocol were used to determine the optimal target design of electronic brachytherapy source. The target thicknesses for maximizing the transmitted X-ray intensity were approximately 1.2 to 1.5 μm for 0° and 90°. In a range of optimal thickness, transmitted X-ray intensity at 90° was approximately 92% of maximum photon intensity. The effects of electron beam shapes on 2D anisotropy functions were investigated at radial distances of 0.5, 1.0, 2.0, 3.0, and 5.0 cm. Minimum variations for all radiation distances and angular ranges were observed for uniform cylindrical electron beam with a radius of 2.0 mm. Anisotropy functions at 0°, F(r, 0° ), were close to unity and slightly more than unity for non-uniform cylindrical (R = 1.0 - 2.0 mm) electron beam and uniform cylindrical electron beam with a radius of 2.0 mm. The angles of target anode between 45° and 50° show minimum fluctuations in the anisotropy functions and are close to unity for F(r, 0° ). The optimal target configurations are a truncated conical-shaped target having an angle between 45° and 50°. It is concluded that tungsten target having the thickness of 1.2 to 1.5 μm and uniform circular with a radius of 2.0 mm as electron beam produces optimal dosimetric characteristics for electronic brachytherapy X-ray source.

AIM In the present study we assessed if postoperative radiotherapy (PORT) using conventional fractionation confers a benefit in cutaneous melanoma patients with lymph node (LN) metastasis. PATIENTS AND METHODS Sixty-two patients with axillary or inguinal LN metastasis were retrospectively reviewed. Twenty-eight patients received PORT. The median RT dose was 50 Gy in 25 fractions. The high-risk group was defined by the presence of any of the following: ≥3 LNs, size ≥3 cm, extranodal extension. RESULTS The median follow-up time was 34 months. PORT showed a significant benefit on 5-year axilla-inguinal recurrence-free survival (RFS) in high-risk patients (RT 100% vs. No-RT 37%, p=0.001). There was also a benefit of RT on 5-year out-field RFS in the high-risk population (RT 93% vs. No-RT 29%, p=0.002). There were no ≥grade 2 lymphedemas after RT. CONCLUSION PORT using conventional fractionation for high-risk LN metastasis from cutaneous melanoma is feasible with comparable regional control and minimal toxicity.

BACKGROUND Soft-tissue sarcomas (STS) of the distal extremities are a rare disease entity, hence proper treatment strategy is not well established. We evaluated the local control, survival and complications of treating sarcomas in the wrist, hand, ankle and foot with limb-sparing surgery (LSS) and postoperative radiotherapy (PORT). PATIENTS AND METHODS Seventeen patients with STS in wrist, hand, ankle and foot who received PORT after LSS from August 2008 to November 2015 were retrospectively reviewed. Primary outcome was 5-year local recurrence-free survival (LRFS). Secondary outcomes were 5-year distant metastasis-free survival (DMFS) and toxicities. RESULTS The median age was 32 (range=12-78) years. The most frequent STS location was the foot in 11 patients (64%) followed by two patients each in the wrist, hand and ankle, respectively. Fourteen patients (82%) underwent wide resection with flap grafts and the same number of patients achieved clear resection margins. The median postoperative radiation dose was 54 (range=46-60) Gy. Five patients also received chemotherapy. At a median follow-up of 39 (range=6-87) months, 5-year LRFS and DMFS were both 100%. Only one patient experienced grade 3 radiation dermatitis and there was no major wound complication. Radiation-induced bone fracture occurred in two patients. CONCLUSION PORT after LSS showed excellent local control for STS in the wrist, hand, ankle and foot. Considering the good local control and saving of limb function without any significant toxicity, the combination of LSS followed by PORT could be an appropriate and safe modality for STS of the distal extremities.

Purpose: To investigate the accuracy of the CyberKnife Xsight Lung Tracking System (XLTS) compared with that of a fiducial-based target tracking system (FTTS) using patient-specific lung phantoms.Methods and Materials: Three-dimensional printing technology was used to make individualized lung phantoms that closely mimicked the lung anatomy of actual patients. Based on planning computed tomographic data from 6 lung cancer patients who underwent stereotactic ablative radiation therapy using the CyberKnife, the volume above a certain Hounsfield unit (HU) was assigned as the structure to be filled uniformly with polylactic acid material by a 3-dimensional printer (3D Edison, Lokit, Korea). We evaluated the discrepancies between the measured and modeled target positions, representing the total tracking error, using 3 log files that were generated during each treatment for both the FTTS and the XLTS. We also analyzed the gamma index between the film dose measured under the FTTS and XLTS.Results: The overall mean values and standard deviations of total tracking errors for the FTTS were 0.36 +/- 0.39 mm, 0.15 +/- 0.64 mm, and 0.15 +/- 0.62 mm for the craniocaudal (CC), left-right (LR), and anteroposterior (AP) components, respectively. Those for the XLTS were 0.38 +/- 0.54 mm, 0.13 +/- 0.18 mm, and 0.14 +/- 0.37 mm for the CC, LR, and AP components, respectively. The average of gamma passing rates was 100% for the criteria of 3%, 3 mm; 99.6% for the criteria of 2%, 2 mm; and 86.8% for the criteria of 1%, 1 mm.Conclusions: The XLTS has segmentation accuracy comparable with that of the FTTS and small total tracking errors. (C) 2015 Elsevier Inc. All rights reserved.

Elderly patients with non-small cell lung cancer (NSCLC) are frequently treated with radiation therapy (RT) alone, due to poor performance status or underlying disease. We investigated the effectiveness of RT over 60 Gy administered alone to NSCLC patients who were unfit or rejecting for combination treatment.

Purpose: To determine failure patterns and survival outcomes of T4N0-1 non-small cell lung cancer (NSCLC) treated with definitive radiotherapy.Materials and Methods: Ninety-five patients with T4N0-1 NSCLC who received definitive radiotherapy with or without chemotherapy from May 2003 to October 2014 were retrospectively reviewed. The standard radiotherapy scheme was 66 Gy in 30 fractions. The main concurrent chemotherapy regimen was 50 mg/m(2) weekly paclitaxel combined with 20 mg/m(2) cisplatin or AUC 2 carboplatin. The primary outcome was overall survival (OS). Secondary outcomes were failure patterns and toxicities.Results: The median age was 64 years (range, 34 to 90 years). Eighty-eight percent of patients (n = 84) had an Eastern Cooperative Oncology Group performance status of 0-1, and 42% (n = 40) experienced pretreatment weight loss. Sixty percent of patients (n = 57) had no metastatic regional lymph nodes. The median radiation dose was EQD2 67.1 Gy (range, 56.9 to 83.3 Gy). Seventy-one patients (75%) were treated with concurrent chemotherapy; of these, 13 were also administered neoadjuvant chemotherapy. At a median follow-up of 21 months (range, 1 to 102 months), 3-year OS was 44%. The 3-year cumulative incidences of local recurrence and distant recurrence were 48.8% and 36.3%, respectively. Pretreatment weight loss and combined chemotherapy were significant factors for OS. Acute esophagitis over grade 3 occurred in three patients and grade 3 chronic esophagitis occurred in one patient. There was no grade 3-4 radiation pneumonitis.Conclusion: Definitive radiotherapy for T4N0-1 NSCLC results in favorable survival with acceptable toxicity rates. Local recurrence is the major recurrence pattern. Intensity modulated radiotherapy and radio-sensitizing agents would be needed to improve local tumor control.

Purpose To evaluate the treatment results in early stage non-small cell lung cancer patients who have undergone fiducial-less CyberKnife radiosurgery (CKRS). Materials and Methods From June 2011 to November 2013, 58 patients underwent CKRS at Asan Medical Center for stage I lung cancer. After excluding 14 patients, we retrospectively reviewed the records of the remaining 44 patients. All analyses were performed using SPSS ver. 21. Results The median age at diagnosis was 75 years. Most patients had inoperable primary lung cancer with a poor pulmonary function test with comorbidity or old age. The clinical stage was IA in 30 patients (68.2%), IB in 14 (31.8%). The mean tumor size was 2.6 cm (range, 1.2 to 4.8 cm), and the tumor was smaller than 2 cm in 12 patients (27.3%). The radiation dose given was 48-60 Gy in 3-4 fractions. In a median follow-up of 23.1 months, local recurrence occurred in three patients (2-year local recurrence-free survival rate, 90.4%) and distant metastasis occurred in 13 patients. All patients tolerated the radiosurgery well, only two patients developing grade 3 dyspnea. The most common complications were radiation-induced fibrosis and pneumonitis. Eight patients died due to cancer progression. Conclusion The results showed that fiducial-less CKRS shows comparable local tumor control and survival rates to those of LINAC-based SABR or CKRS with a fiducial marker. Thus, fiducial-less CKRS using Xsight lung tracking system can be effectively and safely performed for patients with medically inoperable stage I non-small cell lung cancer without any risk of procedure-related complication.

A new electronic x-ray source based on carbon nanotube (CNT) field emitter has been developed for electronically-controlled brachytherapy [1]. The x-ray source is capable of voltages up to 70 kV. The source current and photon beam intensity may be modulated to approximately perform the dose rate of clinically suitable radionuclides such as high-dose rate (HDR) and low-dose rate (LDR) brachytherapy sources. At an operating voltage of 50 kV, the source can produce air kerma rate ranging from 108.1 Gy cm 2 min -1 with a tube current of 252 μA. This study assessed the photon energy spectrum and dose distribution in air of the electronic x-ray brachytherapy source using Monte Carlo code (MCNP6 Beta3).