Wonsik Choi

Planning study for available dose of hypoxic tumor volume using fluorine-18-labeled fluoromisonidazole positron emission tomography for treatment of the head and neck cancer.

PURPOSEnTo investigate the feasibility of fluorine-18-labeled fluoromisonidazole positron emission tomography/computed tomography ((18)F-FMISO PET/CT)-guided intensity-modulated radiotherapy (IMRT) in dose escalation to attack the hypoxic volume of a tumor mass without increasing the normal tissue dose in head and neck cancer patients.nnnMATERIALS AND METHODSnEight consecutive head and neck cancer patients underwent (18)F-FMISO PET/CT simulation. Hypoxic tumor volume (HTV) was defined using a tumor-to-cerebellum ratio (T/C) of 1.3 as the threshold for (18)F-FMISO PET/CT. Dose-escalation plans for treating HTVs using (18)F-FMISO PET/CT-guided IMRT were performed for these patients. The standard plan was 72Gy to the gross tumor volume (GTV) administered as 30 daily fractions of 2.4Gy. In biologically optimized IMRT plans, the daily dose to the HTV ranged from 2.6 to 3.6Gy. Dose-volume histograms (DVHs) were generated as part of each plan, and the results of planning were analyzed.nnnRESULTSnDose-escalation IMRT plans, delivering 30 daily doses of 2.6Gy (total of 78Gy) to the HTVs without increases in normal tissue doses, were feasible for six patients. Further acceptable dose escalation on HTV depended primarily on the primary tumor site and the extent of disease.nnnCONCLUSIONSnIt was possible to dose escalate the HTV radiation to 78Gy in six of eight head and neck cancer patients using (18)F-FMISO PET/CT-guided IMRT.

Verification of Accuracy of CyberKnife Tumor-tracking Radiation Therapy Using Patient-specific Lung Phantoms

PURPOSEnTo 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.nnnMETHODS AND MATERIALSnThree-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 γ index between the film dose measured under the FTTS and XLTS.nnnRESULTSnThe 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 γ 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.nnnCONCLUSIONSnThe XLTS has segmentation accuracy comparable with that of the FTTS and small total tracking errors.

Definitive radiotherapy alone over 60 Gy for patients unfit for combined treatment to stage II-III non-small cell lung cancer: retrospective analysis

BackgroundElderly 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 60xa0Gy administered alone to NSCLC patients who were unfit or rejecting for combination treatment.Methods and materialsFrom April 2002 to July 2010, 83 patients with stage II-III NSCLC, aged over 60xa0years, treated by RT alone with a curative aim were analyzed. Radiation was targeted to the primary tumor and clinically involved lymph nodes. A total dose of 66xa0Gy in 30 fractions (2.2xa0Gy/fraction) was delivered once daily (5 fractions weekly). One month after completing RT, initial tumor responses were evaluated.ResultsMedian age of patients was 73xa0years (range, 60 – 82xa0years). The median survival time was 18.6xa0months (range, 2–135). The actuarial overall survival rates at 2 and 3xa0years were 39xa0% and 23xa0%, and cause-specific survival rate at 2 and 3xa0years were 57xa0% and 47xa0%, respectively. When primary tumor was controlled, the 2- and 3-year CSS were 56xa0% and 45xa0%, but 32xa0% and 23xa0% in those patients with local failure, respectively (Pu2009=u20090.017). Additionally, the local control rate was associated with the initial tumor response (Pu2009=u20090.01). No patient experienced grade 4+ toxicity.ConclusionsFor stage II-III NSCLC patients aged over 60xa0years and unfit or rejecting for combination treatment, RT alone showed promising result. Long-term disease control can be expected if an early tumor response to radiation is achieved, which could result in improved overall survival rates.

Postoperative radiotherapy for ependymoma

Purpose To evaluated the patterns of failure, survival rate, treatment-related toxicity and prognostic factors in postoperative radiotherapy of patients with ependymoma. Materials and Methods Thirty patients who underwent surgery and postoperative radiotherapy for ependymoma between the period of June 1994 and June 2008 were reviewed retrospectively. The age of patients ranged from 21 months to 66 years (median, 19 years). Seventeen patients had grade II ependymoma, and 13 had grade III anaplastic ependymoma according to the World Health Organization grading system. The postoperative irradiation was performed with 4 or 6 MV photon beam with median dose of 52.8 Gy (range, 45 to 63 Gy), and radiation field including 2 cm beyond the preoperative tumor volume. Median follow-up period was 51 months (range, 12 to 172 months). Results Fourteen out of 30 (46.7%) patients experienced recurrence, and 12 of those died. Among those 14 patients who experienced recurrence, 11 were in-field and 3 were out-of-field recurrence. The 5-year overall survival (OS) and progression-free survival (PFS) rates were 66.7% and 56.1%, respectively. On univariate analysis, tumor grade was a statistically significant prognostic factor for OS and PFS. There were two complications after surgery and postoperative radiotherapy, including short stature and facial palsy on the left side. Conclusion We observed good survival rates, and histologic grade was a prognostic factor affecting the OS and PFS. Almost all recurrence occurred in primary tumor site, thus we suggest further evaluation on intensity-modulated radiotherapy or stereotatic radiosurgery for high-risk patients such as who have anaplastic ependymoma.

Asset Management Information in the Social Infrastructure

With the social infrastructure being deteriorated, there is a growing need to introduce the asset management to social infrastructure management in order to increase their value and save budget. Social infrastructure asset management is a new concept of facility management in response to these demands. It is defined as a procedure for collecting and analysing facility maintenance data and for making and practicing an economically optimized management plan. Detailed survey work of asset management business is analyzed in order to derive a strategy for asset management information. The contents of IIMM of New Zealand and the asset management definition of the FHWA of the United States, and representative facility management systems of Korea are analysed. The role between organizations and the relationship between business and organization were analyzed. Information required for asset management and for existing facility management systems is compared with business of asset management. In this thesis, three development strategies are suggested. The first one is to develop core business of asset management while excluding duplicated development. The second one is to divide system`s structure into three layers. And the last one is to share information by interfacing asset management systems with existing facility management systems.

Feasible Optimization of Stereotactic Ablative Radiotherapy Dose by Tumor Size for Stage I Non–small-cell Lung Cancer

Micro‐Abstract The effect of dose escalation of stereotactic ablative radiotherapy, from 48 Gy in 4 fractions (biologically effective dose [BED] = 106 Gy10) to 60 Gy in 4 fractions (BED = 150 Gy10), was evaluated for NSCLC. Tumors ≤ 2 cm had no local recurrence regardless of dose, whereas for tumors > 2 cm, approximately 150 Gy10 BED showed significantly higher local control. 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.

Assessment Items for the Level of Service for Tunnel Facilities from an Asset Management Perspective

Korea was followed by a rapid increase in road construction investment in late 1980s with the help of strong economic conditions. As a result of such investment, it will be expected that there must be a rapid increase in demand for maintenance or rehabilitation of the facilities after 2010. We are developing asset management information systems for enhancing user`s satisfaction and innovating the facility management techniques within a limited budget. We suggested the assessment items for the Level of Service for tunnel facility`s operation and maintenance(O&M), in this study. We have surveyed for the importance of assessment items by considering both user`s viewpoints and facility management agency`s viewpoints. We came to realize the relative importance of the items based on this survey using the Analytic Hierarchy Process(AHP) method proposed by Satty. The relative importance of assessment items in terms of the user`s viewpoint was identified in descending order such as safety, mobility, accessibility, convenience, O&M efficiency, comfort, rural revitalization, environment, and information. Also, the importance of the items in terms of the management agency`s viewpoint was identified in descending order such as safety, mobility, accessibility, environment, rural revitalization, convenience, O&M efficiency, information, and comfort. It means that safety of tunnel facilities is more important than mobility, although which is the basic function of the road facility, both in agency`s and user`s concern. Therefore, the agencies have to pay more attentions and efforts to ensure safety of tunnel facilities when they establish the investment plans for the tunnel facility O&M.

Definitive radiotherapy with or without chemotherapy for clinical stage T4N0-1 non-small cell lung cancer

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/m2 weekly paclitaxel combined with 20 mg/m2 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.

Optimal Timing for the Administration of Capecitabine with Preoperative Chemoradiation for Locally Advanced Rectal Cancer

PURPOSEnCapecitabine is an oral fluoropyrimidine carbamate and it is known as an effective radiosensitizer. Capecitabine and its metabolite reach their peak concentration in the plasma at 1 approximately 2 hours after a single oral administration of capecitabine and the levels fall rapidly thereafter. To verify the radiosensitizing effect of capecitabine that is based on such pharmacokinetic characteristics, we performed a retrospective analysis on the optimal timing of capecitabine administration with performing preoperative chemoradiation for locally advanced rectal cancer.nnnMATERIALS AND METHODSnAmong 171 patients who were treated with preoperative radiotherapy and concurrent capecitabine administration for rectal cancer, 56 patients were administered capecitabine at 1~2 hours before radiotherapy (group A), and at other time in the other 115 patients (group B). Total mesorectal excision was done at 4 to 6 weeks after the completion of chemoradiation. The radiosensitizing effect of capecitabine was evaluated on the basis of the pathological response.nnnRESULTSnComplete pathological regression of the primary tumor was observed in 12 patients (21.4%) for group A and in 11 patients (9.6%) for group B (p=0.031). Residual disease less than 0.5 cm (a good response) was observed in 19 patients (33.9%) for group A and in 23 patients (20.0%) for group B (p=0.038). On multivariate analysis, the capecitabine ingestion time showed marginal significance.nnnCONCLUSIONnWhen performing preoperative chemoradiation for locally advanced rectal cancer, the radiosensitizing effect of capecitabine was enhanced when it was administered 1 hour before radiotherapy.

A 10-year clinical outcome of radiotherapy as an adjuvant or definitive treatment for primary tracheal adenoid cystic carcinoma

BackgroundTo 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.MethodsA 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.ResultsThirteen 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 59.4xa0Gy for adjuvant and 74.4xa0Gy 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 123xa0months, 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 >5xa0years. 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.ConclusionsAdjuvant 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.