Standard follow-up after curative surgery for advanced gastric cancer: secondary analysis of a multicentre randomized clinical trial (KLASS-02).

BACKGROUND: The benefit of regular follow-up after curative resection for gastric cancer is controversial as there is no evidence that it will improve survival. This study assessed whether regular follow-up leads to improved survival in patients after surgery for gastric cancer. METHODS: A secondary analysis was undertaken of patients who participated in an RCT of laparoscopic versus open distal gastrectomy for advanced gastric cancer between November 2011 and April 2015. Depending on whether patients were compliant with the initial trial follow-up protocol or not, they were analysed as having had either regular or irregular follow-up. Clinicopathological characteristics, recurrence patterns, detection, treatments, and survival were compared between the groups. RESULTS: The regular and irregular follow-up groups comprised 712 and 263 patients respectively. Disease recurrence within 36 months was more common in the regular group than in the irregular group (17.0 versus 11.4 per cent; P = 0.041). Recurrence patterns did not differ between the groups. The 3-year recurrence-free survival rate was worse in the regular than in the irregular group (81.2 versus 86.5 per cent; P = 0.031). However, the 5-year overall survival rate was comparable (84.5 versus 87.5 per cent respectively; P = 0.160). Multivariable analysis revealed that type of follow-up was not an independent factor affecting 5-year overall survival. CONCLUSION: Regular follow-up after radical gastrectomy was not associated with improved overall survival.

Surgeon Quality Control and Standardization of D2 Lymphadenectomy for Gastric Cancer: A Prospective Multicenter Observational Study (KLASS-02-QC).

OBJECTIVE: To qualify surgeons to participate in a randomized trial comparing laparoscopic and open distal D2 gastrectomy for advanced gastric cancer. SUMMARY OF BACKGROUND DATA: No studies have sought to qualify surgeons for a randomized trial comparing laparoscopic and open D2 gastrectomy for advanced gastric cancer. METHODS: We conducted a multicenter prospective observational study evaluating unedited videos of laparoscopic and open D2 gastrectomy performed by 27 surgeons. Surgeons performed 3 of each laparoscopic and open distal gastrectomies with D2 lymphadenectomy for gastric cancer. Five peers reviewed each unedited video using a video assessment form. Based on experts' review of videos, a separate review committee decided surgeons as "Qualified" or "Not-qualified." RESULTS: Twelve surgeons (44.4%) were qualified on initial evaluation whereas the other 15 surgeons were not. Another 9 surgeons were finally qualified after re-evaluation. The median score for Qualified was significantly higher than Not-qualified (P < 0.001).Significant differences between Qualified and Not-qualified were noted both in operation type and in all evaluation area of surgical skill, perigastric, and extra-perigastric lymphadenectomy, although the inter-rater variability of the assessment score was low (kappa = 0.285). However, Not-qualified surgeons' scores improved upon re-evaluation of resubmitted videos.When compared laparoscopy with open surgery, median scores were similar between the 2 groups (P = 0.680). However, open gastrectomy scores for surgical skills were significantly higher than for laparoscopic surgery (P = 0.016). CONCLUSIONS: Our surgeon quality control study for gastrectomy represents a milestone in surgical standardization for surgical clinical trials. Our methods could also serve as a system for educating surgeons and assessing surgical proficiency.

Comparison of surgical outcomes among different methods of esophagojejunostomy in laparoscopic total gastrectomy for clinical stage I proximal gastric cancer: results of a single-arm multicenter phase II clinical trial in Korea, KLASS 03.

BACKGROUND: Laparoscopic distal gastrectomy for early gastric cancer has been widely accepted, but laparoscopic total gastrectomy has still not gained popularity because of technical difficulty and unsolved safety issue. We conducted a single-arm multicenter phase II clinical trial to evaluate the safety and the feasibility of laparoscopic total gastrectomy for clinical stage I proximal gastric cancer in terms of postoperative morbidity and mortality in Korea. The secondary endpoint of this trial was comparison of surgical outcomes among the groups that received different methods of esophagojejunostomy (EJ). METHODS: The 160 patients of the full analysis set group were divided into three groups according to the method of EJ, the extracorporeal circular stapling group (EC; n = 45), the intracorporeal circular stapling group (IC; n = 64), and the intracorporeal linear stapling group (IL; n = 51). The clinicopathologic characteristics and the surgical outcomes were compared among these three groups. RESULTS: There were no significant differences in the early complication rates among the three groups (26.7% vs. 18.8% vs. 17.6%, EC vs. IC vs. IL; p = 0.516). The length of mini-laparotomy incision was significantly longer in the EC group than in the IC or IL group. The anastomosis time was significantly shorter in the EC group than in the IL group. The time to first flatus was significantly shorter in the IL group than in the EC group. The long-term complication rate was not significantly different among the three groups (4.4% vs. 12.7% vs. 7.8%; EC vs. IC vs. IL; p = 0.359), however, the long-term incidence of EJ stenosis in IC group (10.9%) was significantly higher than in EC (0%) and IL (2.0%) groups (p = 0.020). CONCLUSIONS: The extracorporeal circular stapling and the intracorporeal linear stapling were safe and feasible in laparoscopic total gastrectomy, however, intracorporeal circular stapling increased EJ stenosis.

Short-term Outcomes of a Multicenter Randomized Controlled Trial Comparing Laparoscopic Distal Gastrectomy With D2 Lymphadenectomy to Open Distal Gastrectomy for Locally Advanced Gastric Cancer (KLASS-02-RCT).

OBJECTIVE: The aim of the study was to evaluate the short-term outcomes of KLASS-02-RCT, a multicenter randomized controlled trial comparing laparoscopic distal gastrectomy (LDG) with D2 lymphadenectomy with open distal gastrectomy (ODG). SUMMARY BACKGROUND DATA: Although several benefits of laparoscopic gastric cancer surgery have been reported, strong evidence is still limited, especially in locally advanced gastric cancer which requires extensive lymph node dissection. METHODS: Enrollment criteria included histologically confirmed cT2-4a and N0-1 gastric adenocarcinoma. Thirty-day morbidity, 90-day mortality, postoperative pain, and recovery were compared between LDG and ODG groups. RESULTS: A total of 1050 patients were randomly assigned to LDG (n = 526) or ODG group (n = 524) between November 2011 and April 2015. After excluding patients who received bypass or no surgery, 1011 patients were analyzed as actual treatment group. Mean number of totally retrieved lymph nodes was similar in both groups (LDG = 46.6 vs ODG = 47.4, P = 0.451). Early morbidity rate was significantly lower after LDG (16.6%) than after ODG (24.1%; P = 0.003). Postoperative analgesics use and patients' reported pain score were significantly lower after LDG. First day of flatus was earlier after LDG (3.5 vs 3.7 d, P = 0.025) and postoperative hospital stay was shorter in LDG group (8.1 vs 9.3 d, P = 0.005). Ninety days' mortality rate was similar in both groups (LDG = 0.4% vs ODG = 0.6%, P = 0.682). CONCLUSIONS: Laparoscopic distal gastrectomy with D2 lymphadenectomy for locally advanced gastric cancer shows benefits in terms of lower complication rate, faster recovery, and less pain compared with open surgery.

Operation time as a simple indicator to predict the overcoming of the learning curve in gastric cancer surgery: a multicenter cohort study.

BACKGROUND: The aim of this study is to identify an indicator to predict the overcoming of the learning curve of distal gastrectomy in gastric cancer surgery. METHOD: A retrospective multicenter cohort study was conducted in 2100 patients who underwent radical distal gastrectomy performed by nine surgeons in eight hospitals between 2001 and 2006. For each surgeon, an individual CUSUM chart was formulated in terms of operation time or clinical outcomes, including severe complications, number of retrieved lymph nodes, positive resection margin, and hospital stay. The actual changing points (CPs) of the CUSUM charts were analyzed. Based on the CP, patients were divided into pre-CP and post-CP groups, and the clinicopathologic outcomes and survival data were compared between the groups. RESULTS: CP determined by operation time was more reliable than CP determined by a combination of clinical outcomes, as the former was correlated not only with short-term outcomes but also with survival. The outcomes were superior in the post-CP group in terms of numbers of harvested lymph nodes, sufficient lymph node harvesting (> 15), and negative proximal margins. In a survival analysis, the post-CP group showed better survival than the pre-CP group in stage II (76% vs 86.1% p = 0.010) and stage III (51.5% vs 60.6% p = 0.042). CONCLUSION: Overcoming the learning curve of distal gastrectomy for gastric cancer can be better predicted by operation time rather than by a combination of postoperative clinical parameters. It is recommended that surgeons initially operate on early stage cancer patients before overcoming the learning curve.

A feasibility study of laparoscopic total gastrectomy for clinical stage I gastric cancer: a prospective multi-center phase II clinical trial, KLASS 03.

BACKGROUND: With improved short-term surgical outcomes, laparoscopic distal gastrectomy has rapidly gained popularity. However, the safety and feasibility of laparoscopic total gastrectomy (LTG) has not yet been proven due to the difficulty of the technique. This single-arm prospective multi-center study was conducted to evaluate the use of LTG for clinical stage I gastric cancer. METHODS: Between October 2012 and January 2014, 170 patients with pathologically proven, clinical stage I gastric adenocarcinoma located at the proximal stomach were enrolled. Twenty-two experienced surgeons from 19 institutions participated in this clinical trial. The primary end point was the incidence of postoperative morbidity and mortality at postoperative 30 days. The severity of postoperative complications was categorized according to Clavien-Dindo classification, and the incidence of postoperative morbidity and mortality was compared with that in a historical control. RESULTS: Of the enrolled patients, 160 met criteria for inclusion in the full analysis set. Postoperative morbidity and mortality rates reached 20.6% (33/160) and 0.6% (1/160), respectively. Fifteen patients (9.4%) had grade III or higher complications, and three reoperations (1.9%) were performed. The incidence of morbidity after LTG in this trial did not significantly differ from that reported in a previous study for open total gastrectomy (18%). CONCLUSIONS: LTG performed by experienced surgeons showed acceptable postoperative morbidity and mortality for patients with clinical stage I gastric cancer.

A Novel Prediction Model of Prognosis After Gastrectomy for Gastric Carcinoma: Development and Validation Using Asian Databases.

OBJECTIVE: The prognoses of gastric cancer patients vary greatly among countries. Meanwhile, tumor-node-metastasis (TNM) staging system shows limited accuracy in predicting patient-specific survival for gastric cancer. The objective of this study was to create a simple, yet universally applicable survival prediction model for surgically treated gastric cancer patients. SUMMARY BACKGROUND DATA: A prediction model of 5-year overall survival for surgically treated gastric cancer patients regardless of curability was developed using a test data set of 11,851 consecutive patients. METHODS: The model's coefficients were selected based on univariate and multivariate analysis of patient, tumor, and surgical factors shown to significantly impact survival using a Cox proportional hazards model. For internal validation, discrimination was calculated with the concordance index (C-statistic) using the bootstrap method and calibration assessed. The model was externally validated using 4 data sets from 3 countries. RESULTS: Our model's C-statistic (0.824) showed better discrimination power than current tumor-node-metastasis staging (0.788) (P < 0.0001). Bootstrap internal validation demonstrated that coefficients remained largely unchanged between iterations, with an average C-statistic of 0.822. The model calibration was accurate in predicting 5-year survival. In the external validation, C-statistics showed good discrimination (range: 0.798-0.868) in patient data sets from 4 participating institutions in 3 different countries. CONCLUSIONS: Utilizing clinically practical patient, tumor, and surgical information, we developed a universally applicable prediction model for accurately determining the 5-year overall survival of gastric cancer patients after gastrectomy. Our predictive model was also valid in patients who underwent noncurative resection or inadequate lymphadenectomy.

Decreased Morbidity of Laparoscopic Distal Gastrectomy Compared With Open Distal Gastrectomy for Stage I Gastric Cancer: Short-term Outcomes From a Multicenter Randomized Controlled Trial (KLASS-01).

OBJECTIVE: To determine the safety of laparoscopy-assisted distal gastrectomy (LADG) compared with open distal gastrectomy (ODG) in patients with clinical stage I gastric cancer in Korea. BACKGROUND: There is still a lack of large-scale, multicenter randomized trials regarding the safety of LADG. METHODS: A large-scale, phase 3, multicenter, prospective randomized controlled trial was conducted. The primary end point was 5-year overall survival. Morbidity within 30 postoperative days and surgical mortality were compared to evaluate the safety of LADG as a secondary end point RESULTS: : A total of 1416 patients were randomly assigned to the LADG group (n = 705) or the ODG group (n = 711) between February 1, 2006, and August 31, 2010, and 1384 patients were analyzed for modified intention-to-treat analysis (ITT) and 1256 were eligible for per protocol (PP) analysis (644 and 612, respectively). In the PP analysis, 6 patients (0.9%) needed open conversion in the LADG group. The overall complication rate was significantly lower in the LADG group (LADG vs ODG; 13.0% vs 19.9%, P = 0.001). In detail, the wound complication rate of the LADG group was significantly lower than that of the ODG group (3.1% vs 7.7%, P < 0.001). The major intra-abdominal complication (7.6% vs 10.3%, P = 0.095) and mortality rates (0.6% vs 0.3%, P = 0.687) were similar between the 2 groups. Modified ITT analysis showed similar results with PP analysis. CONCLUSIONS: LADG for patients with clinical stage I gastric cancer is safe and has a benefit of lower occurrence of wound complication compared with conventional ODG.

Assessment of laparoscopic stomach preserving surgery with sentinel basin dissection versus standard gastrectomy with lymphadenectomy in early gastric cancer-A multicenter randomized phase III clinical trial (SENORITA trial) protocol.

BACKGROUND: Along with the marked increase in early gastric cancer (EGC) in the Eastern countries, there has been an effort to adopt the sentinel node concept in EGC to preserve gastric function and reduce the occurrence of postoperative complications. Based on promising results from a previous quality control study, this prospective multicenter randomized controlled phase III clinical trial aims to elucidate the oncologic safety of laparoscopic stomach-preserving surgery with sentinel basin dissection (SBD) compared to a standard laparoscopic gastrectomy. METHODS/DESIGN: This trial is an investigator-initiated, open-label, multicenter randomized controlled phase III trial with a non-inferiority design. Patients diagnosed with a single lesion of clinical stage T1N0M0 gastric adenocarcinoma, with a diameter of 3 cm or less are eligible for the present study. A total of 580 patients (290 per group) will be randomized to either laparoscopic stomach-preserving surgery with SBD or standard surgery. The primary end-point is 3-year disease-free survival (DFS) and the secondary endpoints include postoperative morbidity and mortality, quality of life, 5-year DFS, and overall survival. Qualified investigators who completed the prior quality control study are exclusively allowed to participate in this phase III clinical trial. DISCUSSION: The proposed trial is expected to verify whether laparoscopic stomach-preserving surgery with SBD achieves similar oncologic outcomes and improved quality of life compared to a standard gastrectomy in EGC patients. TRIAL REGISTRATION: This study was registered at the NIH ClinicalTrial.gov database ( NCT01804998 ) on March 4th, 2013.

Learning curve for gastric cancer surgery based on actual survival.

BACKGROUND: The aim of this study was to investigate learning curves for surgeons performing D2 lymph node dissection based on actual patient survival. METHODS: A total of 3,284 patients with gastric cancer who underwent curative intent gastric cancer surgery by nine surgeons in eight Korean hospitals between 2001 and 2006 were included. Each surgeon's experience was coded as the number of D1 + ß or more gastrectomies performed before that for each patient, which indicates the surgeon's total number of prior surgical experiences. Surgeon experience was grouped into two sets of categories. The set of categories included four groups of experience: ≤50, 51-100, 101-200, and >200 applicable operations. Multivariate survival time regression models were used to evaluate the association between surgeon experience and overall survival. RESULTS: The learning curve for gastric cancer survival after open gastric cancer surgery was steep and did not reach a plateau until a surgeon completed 100 operations. Overall survival rate was the lowest among patients treated by a surgeon with an experience of 50-100 cases. The overall survival of patients at 5 years when the surgeon had a history of more than 100 experiences was higher in each stage than that when the surgeon had a history of fewer than 100 experiences. CONCLUSION: As a surgeon's experience increases, survival after gastric cancer surgery improves. Special attention needs to be paid to the second period of surgeon experience because survival of patients in this period was the lowest.

Quality of Life and Nutritional Outcomes of Stomach-Preserving Surgery for Early Gastric Cancer: A Secondary Analysis of the SENORITA Randomized Clinical Trial.

Importance: The Sentinel Node Oriented Tailored Approach (SENORITA) randomized clinical trial evaluated quality of life (QoL) and nutritional outcomes between the laparoscopic sentinel node navigation surgery (LSNNS) and laparoscopic standard gastrectomy (LSG). However, there has been no report on the QoL and nutritional outcomes of patients who underwent stomach-preserving surgery among the LSNNS group. Objective: To compare long-term QoL and nutritional outcomes between patients who underwent stomach-preserving surgery and those who underwent standard gastrectomy and to identify factors associated with poor QoL outcomes in patients who underwent stomach-preserving surgery. Design, Setting, and Participants: This study is a secondary analysis of the SENORITA trial, a randomized clinical trial comparing LSNNS with LSG. Patients from 7 tertiary or general hospitals across the Republic of Korea were enrolled from March 2013 to December 2016, with follow-up through 5 years. Data were analyzed between August and September 2022. Among trial participants, patients who underwent actual laparoscopic standard gastrectomy in the LSG group and those who underwent stomach-preserving surgery in the LSNNS group were included. Patients who did not complete the baseline or any follow-up questionnaire were excluded. Intervention: Stomach-preserving surgery vs standard gastrectomy. Main Outcomes and Measures: Overall European Organization for Research and Treatment of Cancer QoL Questionnaire Core 30 (EORTC QLQ-C30) and stomach module (STO22) scores, body mass index, hemoglobin, protein, and albumin levels. Results: A total of 194 and 257 patients who underwent stomach-preserving surgery and standard gastrectomy, respectively, were included in this study (mean [SD] age, 55.6 [10.6] years; 249 [55.2%] male). The stomach-preserving group had better QoL scores at 3 months postoperatively in terms of physical function (87.2 vs 83.9), dyspnea (5.9 vs 11.2), appetite loss (13.1 vs 19.4), dysphagia (8.0 vs 12.7), eating restriction (10.9 vs 18.2), anxiety (29.0 vs 35.2), taste change (7.4 vs 13.0), and body image (19.5 vs 27.2). At 1 year postoperatively, the stomach-preserving group had significantly higher body mass index (23.9 vs 22.1, calculated as weight in kilograms divided by height in meters squared) and hemoglobin (14.3 vs 13.3 g/dL), albumin (4.3 vs 4.25 g/dL), and protein (7.3 vs 7.1 g/dL) levels compared to the standard group. Multivariable analyses showed that tumor location (greater curvature, lower third) was favorably associated with global health status (ß, 10.5; 95% CI, 3.2 to 17.8), reflux (ß, -8.4; 95% CI, -14.7 to -2.1), and eating restriction (ß, -5.7; 95% CI, -10.3 to -1.0) at 3 months postoperatively in the stomach-preserving group. Segmental resection was associated with risk of diarrhea (ß, 40.6; 95% CI, 3.1 to 78.1) and eating restriction (ß, 15.1; 95% CI, 1.1 to 29.1) at 3 years postoperatively. Conclusions and Relevance: Stomach-preserving surgery after sentinel node evaluation was associated with better long-term QoL and nutritional outcomes than standard gastrectomy. These findings may help facilitate decision-making regarding treatment for patients with early-stage gastric cancer. Trial Registration: ClinicalTrials.gov Identifier: NCT01804998.

Novel method of producing nanoparticles for gadolinium-scintillator-based digital radiography.

Radiation image sensor properties affect the dose of radiation that patients are exposed to in a clinical setting. Numerous radiation imaging systems use scintillators as materials that absorb radiation. Rare-earth scintillators produced from elements such as gadolinium, yttrium, lutetium, and lanthanum have been investigated to improve the properties of radiation imaging systems. Although such rare-earth scintillators are manufactured with a bulk structure, they exhibit low resolution and low efficiency when they are used as conversion devices. Nanoscintillators have been proposed and researched as a possible solution to these problems. According to the research, the optical properties and size of fine scintillators are affected by the sintering temperature used to produce nanoscintillators instead of the existing bulk-structured scintillators. Therefore, the main purpose of this research is to develop radiation-imaging sensors based on nanoscintillators in order to evaluate the quantitative properties of various scintillators produced under various conditions such as sintering temperature. This is accomplished by measuring acquired phantom images, and modulation transfer functions (MTFs) for complementary-symmetry metal-oxide-semiconductor (CMOS) image sensors under the same X-ray conditions. Low-temperature solution combustion was used to produce fine scintillators consisting of 5 wt% of europium as an activator dopant in a Gd2O3 scintillator host. Variations in the characteristics of the fine scintillators were investigated. The characteristics of fine scintillators produced at various sintering temperatures (i.e., 600, 800, or 1000 degrees C) and with a europium concentration of 0.5 wt% were also analyzed to determine the optimal conditions for synthesizing the fine scintillators.

Clinical outcomes compared between laparoscopic and open appendectomy in pregnant women.

BACKGROUND: Despite the initial absolute or relative contraindication of laparoscopic surgery during pregnancy, in the last decade, laparoscopic appendectomy (LA) has been performed in pregnant women. But few studies compare the outcomes of LA compared with open appendectomy (OA). We investigated clinical outcomes to evaluate the safety and efficacy of LA compared with OA in pregnant women. METHODS: We recruited consecutive pregnant patients with a diagnosis of acute appendicitis who were undergoing LA or OA between May 2007 and August 2011 into the study. RESULTS: Sixty-one patients (22 LA and 39 OA) enrolled in our study. There were no significant differences in duration of surgery, postoperative complication rate and obstetric and fetal outcomes, including incidence of preterm labour, delivery type, gestation age at delivery, birth weight and APGAR scores between the 2 groups. However, the LA group had shorter time to first flatus (2.4 ± 0.4 d v. 4.0 ± 1.7 d, p = 0.034), earlier time to oral intake (2.3 ± 1.6 d v. 4.1 ± 1.9 d, p = 0.023) and shorter postoperative hospital stay (4.2 ± 2.9 d v. 6.9 ± 3.7 d, p = 0.043) than the OA group. CONCLUSION: Laparoscopic appendectomy is a clinically safe and effective procedure in all trimesters of pregnancy and should be considered as a standard treatment alternative to OA. Further evaluation including prospective randomized clinical trials comparing LA with OA are needed to confirm our results.

CONTEXTE: Malgré une contre-indication initiale absolue ou relative de l'opération laparoscopique durant la grossesse au cours de la dernière décennie, on a eu recours à l'appendicectomie laparoscopique (AL) chez des femmes enceintes. Mais peu d'études ont comparé les résultats de l'AL à ceux de l'appendicectomie ouverte (AO). Nous avons analysé les résultats cliniques pour comparer l'innocuité et l'efficacité de l'AL à celles de l'AO chez les femmes enceintes. MÉTHODES: Pour la présente étude, nous avons recruté des patientes enceintes consécutives porteuses d'un diagnostic d'appendicite aiguë qui ont dû subir une AL ou une AO entre mai 2007 et août 2011. RÉSULTANTS: Soixante-et-une patientes (22 soumises à l'AL et 39 à l'AO) ont été inscrites à notre étude. Nous n'avons noté aucune différence significative pour ce qui est de la durée de l'intervention chirurgicale, du taux de complications postopératoires et des résultats obstétricaux et fœtaux, y compris l'incidence du travail prématuré, le type d'accouchement, l'âge gestationnel et le poids à la naissance et les indices d'APGAR entre les 2 groupes. Toutefois, le groupe soumis à l'AL a moins tardé à présenter des flatuosités (2,4 ± 0,4 j c. 4,0 ± 1,7 j, p = 0,034), a commencé à s'alimenter par la bouche plus tôt (2,3 ± 1,6 j c. 4,1 ± 1,9 j, p = 0,023) et a connu un séjour hospitalier postopératoire plus bref (4,2 ± 2,9 j c. 6,9 ± 3,7 j, p = 0,043) comparativement au groupe soumis à l'AO. CONCLUSIONS: L'appendicectomie laparoscopique est une intervention sécuritaire et efficace au plan clinique durant les 3 trimestres de la grossesse, et il faut l'envisager comme solution de rechange thérapeutique standard à l'AO. Il faudra une évaluation plus approfondie pour confirmer nos résultats, y compris au moyen d'essais cliniques randomisés prospectifs comparant l'AL à l'AO.

Evaluation of the water-equivalent characteristics of the SP34 plastic phantom for film dosimetry in a clinical linear accelerator.

In this study, some confusing points about electron film dosimetry using white polystyrene suggested by international protocols were verified using a clinical linear accelerator (LINAC). According to international protocol recommendations, ionometric measurements and film dosimetry were performed on an SP34 slab phantom at various electron energies. Scaling factor analysis using ionometric measurements yielded a depth scaling factor of 0.923 and a fluence scaling factor of 1.019 at an electron beam energy of <10 MeV (i.e., R50 < 4.0 g/cm2). It was confirmed that the water-equivalent characteristics were similar because they have values similar to white polystyrene (i.e., depth scaling factor of 0.922 and fluence scaling factor of 1.019) presented in international protocols. Furthermore, percentage depth dose (PDD) curve analysis using film dosimetry showed that when the density thickness of the SP34 slab phantom was assumed to be water-equivalent, it was found to be most similar to the PDD curve measured using an ionization chamber in water as a reference medium. Therefore, we proved that the international protocol recommendation that no correction for measured depth dose is required means that no scaling factor correction for the plastic phantom is necessary. This study confirmed two confusing points that could occur while determining beam characteristics using electron film dosimetry, and it is expected to be used as basic data for future research on clinical LINACs.

Consistency of dose rates after applying machine-specific reference correction factors for the gamma knife 16 mm collimator field.

BACKGROUND: The machine-specific reference (msr) correction factors ( k Q msr , Q 0 f msr , f ref $k_{{Q_{{\rm{msr}}}},\;{Q_0}}^{{f_{{\rm{msr}}}},{f_{{\rm{ref}}}}}$ ) were introduced in International Atomic Energy Agency (IAEA) Technical Report Series 483 (TRS-483) for reference dosimetry of small fields. Several correction factor sets exist for a Leksell Gamma Knife (GK) Perfexion or Icon. Nevertheless, experiments have not rigorously validated the correction factors from different studies. PURPOSE: This study aimed to assess the role and accuracy of k Q msr , Q 0 f msr , f ref $k_{{Q_{{\rm{msr}}}},\;{Q_0}}^{{f_{{\rm{msr}}}},{f_{{\rm{ref}}}}}$ values in determining the absorbed dose rates to water in the reference dosimetry of Gamma Knife. METHODS: The dose rates in the 16 mm collimator field of a GK were determined following the international code of practices with three ionization chambers: PTW T31010, PTW T31016 (PTW Freiberg GmbH, New York, NY), and Exradin A16 (Standard Imaging, Inc., Middleton, WI). A chamber was placed at the center of a solid water phantom (Elekta AB, Stockholm, Sweden) using a detector-specific insert. The reference point of the ionization chamber was confirmed using cone-beam CT images. Consistency checks were repeated five times at a GK site and performed once at seven GK sites. Correction factors from six simulations reported in previous studies were employed. Variations in the dose rates and relative dose rates before and after applying the k Q m s r , Q 0 f m s r , f r e f $k_{{Q_{msr}},\;{Q_0}}^{{f_{msr}},{f_{ref}}}$ were statistically compared. RESULTS: The standard deviation of the dose rates measured by the three chambers decreased significantly after any correction method was applied (p = 0.000). When the correction factors of all studies were averaged, the standard deviation was reduced significantly more than when any single correction method was applied (p ≤ 0.030), except for the IAEA TRS-483 correction factors (p = 0.148). Before any correction was applied, there were statistically significant differences among the relative dose rates measured by the three chambers (p = 0.000). None of the single correction methods could remove the differences among the ionization chambers (p ≤ 0.038). After TRS-483 correction, the dose rate of Exradin A16 differed from those of the other two chambers (p ≤ 0.025). After the averaged factors were applied, there were no statistically significant differences between any pairs of chambers according to Scheffe's post hoc analyses (p ≥ 0.051); however, PTW T31010 differed from PTW 31016 according to Tukey's HSD analyses (p = 0.040). CONCLUSION: The k Q msr , Q 0 f msr , f ref $k_{{Q_{{\rm{msr}}}},\;{Q_0}}^{{f_{{\rm{msr}}}},{f_{{\rm{ref}}}}}$ significantly reduced variations in the dose rates measured by the three ionization chambers. The mean correction factors of the six simulations produced the most consistent results, but this finding was not explicitly proven in the statistical analyses.

Long-term outcomes after laparoscopy-assisted gastrectomy for advanced gastric cancer: a large-scale multicenter retrospective study.

BACKGROUND: Recently, the number of laparoscopic procedures for gastric cancer has increased rapidly. Laparoscopic surgery is reported to have many advantages over open gastrectomy with oncologic safety in early gastric cancer. However, there were few reports on long-term outcomes of laparoscopy-assisted gastrectomy (LAG) for advanced gastric cancer (AGC). The aim of this study was to investigate long-term survival outcomes after LAG for AGC. METHODS: The data of 1,485 patients who underwent LAG between April 1998 and December 2005 by ten surgeons at ten hospitals were collected retrospectively. Among them, 239 patients who were diagnosed with AGC on final pathologic examination were enrolled in the present study to investigate long-term clinical outcomes. RESULTS: The ratio of male to female patients was 151:88 and the mean age was 57.1 years. One hundred ninety-three subtotal gastrectomies, 41 total gastrectomies, and 5 proximal gastrectomies were performed. D1 + α, D1 + ß, and D2 lymph node dissections were performed for 14, 62, and 163 cases, respectively. The median follow-up period was 55.4 months. The overall 5-year survival rate of the 239 AGC patients was 78.8% and the disease-specific 5-year survival rate was 85.6%. The 5-year survival rates of the TNM staging system's (7th ed.) stages were 90.5% (stage Ib, n = 86), 86.4% (stage IIa, n = 53), 78.3% (stage IIb, n = 44), 52.8% (stage IIIa, n = 24), 52.9% (stage IIIb, n = 24), and 37.5% (stage IIIc, n = 8) (p < 0.001). CONCLUSION: The long-term survival outcome rates of LAG for AGC in the present study were comparable to those previously reported for open gastrectomy. Based on the present results, a well-designed phase III trial comparing LAG and open gastrectomy for AGC will be needed to affirm the validity of LAG for AGC.

Effect of non-curative endoscopic submucosal dissection on short-term outcomes of subsequent surgery for early gastric cancer.

BACKGROUND: With growing incidence of early gastric cancer (EGC), endoscopic submucosal dissection (ESD) is widely performed as a standard treatment for mucosal cancer. Due to the increasing application of ESD, the number of non-curative resection after ESD is also growing, leading to escalating number of patients who require additional gastrectomy with lymph node dissection after non-curative ESD. However, effects of ESD prior to surgery on technical difficulties during operation for EGC remain unclear. Therefore, this study aimed to determine the effect of non-curative ESD on short-term surgical outcomes in patients who underwent additional surgical treatment using propensity score matching method. METHODS: To evaluate the effect of ESD on short-term surgical outcomes in patients who underwent additional surgical treatment after a non-curative ESD procedure, patients were divided into two groups: (1) those who underwent additional gastrectomy after non-curative resection of ESD [ESD + Surgery (ES) Group], and (2) those who underwent gastrectomy as the initial treatment [Surgery Only (SO) Group]. To minimize differences in baseline demographic features that could potentially be associated with short-term outcomes, propensity-scored matching analysis was performed. RESULTS: After propensity-scored matching (1:1 matching), 140 patients altogether were selected and analyzed in this study. Complications were experienced by 18 (25.7%) patients in the ES group and 13 (18.6%) patients in the SO group, showing no significant (p < 0.416) difference between the two groups. CONCLUSIONS: Additional surgery after non-curative ESD can be safely applied, even within one month after ESD in terms of short-term complications.

Clinical Efficacy of an Electronic Portal Imaging Device versus a Physical Phantom Tool for Patient-Specific Quality Assurance.

Pre-treatment patient-specific quality assurance (QA) is critical to prevent radiation accidents. The electronic portal imaging device (EPID) is a dose measurement tool with good resolution and a low volume-averaging effect. EPIbeam­an EPID-based portal dosimetry software­has been newly installed in three institutions in Korea. This study evaluated the efficacy of the EPID-based patient-specific QA tool versus the PTW729 detector (a previously used QA tool) based on gamma criteria and planning target volume (PTV). A significant difference was confirmed through the R statistical analysis software. The average gamma passing rates of PTW729 and EPIbeam were 98.73% and 99.60% on 3 mm/3% (local), 96.66% and 97.91% on 2 mm/2% (local), and 88.41% and 74.87% on 1 mm/1% (local), respectively. The p-values between them were 0.015 (3 mm/3%, local), 0.084 (2 mm/2%, local), and less than 0.01 (1 mm/1%, local). Further, the average gamma passing rates of PTW 729 and EPIbeam according to PTV size were 99.55% and 99.91% (PTV < 150 cm3) and 97.91% and 99.28% (PTV > 150 cm3), respectively. The p-values between them were 0.087 (PTV < 150 cm3) and 0.036 (PTV > 150 cm3). These results confirm that EPIbeam can be an effective patient-specific QA tool.

Local complications are related to poor long-term outcome in patients undergoing curative gastrectomy for advanced gastric cancer.

Purpose: The present study was performed to investigate the effects of local complications (LC) on long-term survival and cancer recurrence in patients undergoing curative gastrectomy for gastric cancer. Methods: We analyzed 2,627 patients after curative gastrectomy for gastric cancer between January 2001 and December 2006. Patients were classified into groups no complications (NC), LC, or systemic complications (SC). Results: Among the 2,627 patients, 475 patients developed complications (LC group [n=374, 14.2%] and SC group [n=101, 3.9%]). The 5-year cancer-specific survival rate was significantly poorer in the LC group compared to the NC and SC groups (LC, 78.0%; NC, 85.4%; SC, 80.2%; P=0.007). The occurrence of LC was identified as a significant independent prognostic factor for overall and cancer-specific survival (hazard ratio [HR], 2.08; 95% confidence interval [CI], 1.46-2.97; P=0.001 and HR, 1.77; 95% CI, 1.12-2.81; P=0.015). The tumor recurrence rates were higher in the LC group than the in other two groups (LC, 23.5%; NC, 15.4%; SC, 15.8%; P<0.001). The occurrence of LC was an independent predictor of tumor recurrence in patients undergoing curative gastrectomy for gastric cancer (HR, 1.55; 95% CI, 1.11-2.17; P=0.011). Conclusion: LC are associated with adverse long-term outcomes in patients after curative gastrectomy for advanced gastric cancer.

Early experience of laparoscopic resection and comparison with open surgery for gastric gastrointestinal stromal tumor: a multicenter retrospective study.

The advantages of laparoscopic resection over open surgery in the treatment of gastric gastrointestinal stromal tumor (GIST) are not conclusive. This study aimed to evaluate the postoperative and oncologic outcome of laparoscopic resection for gastric GIST, compared to open surgery. We retrospectively reviewed the prospectively collected database of 1019 patients with gastric GIST after surgical resection at 13 Korean and 2 Japanese institutions. The surgical and oncologic outcomes were compared between laparoscopic and open group, through 1:1 propensity score matching (PSM). The laparoscopic group (N = 318) had a lower rate of overall complications (3.5% vs. 7.9%, P = 0.024) and wound complications (0.6% vs. 3.1%, P = 0.037), shorter hospitalization days (6.68 ± 4.99 vs. 8.79 ± 6.50, P < 0.001) than the open group (N = 318). The superiority of the laparoscopic approach was also demonstrated in patients with tumors larger than 5 cm, and at unfavorable locations. The recurrence-free survival was not different between the two groups, regardless of tumor size, locational favorableness, and risk classifications. Cox regression analysis revealed that tumor size larger than 5 cm, higher mitotic count, R1 resection, and tumor rupture during surgery were independent risk factors for recurrence. Laparoscopic surgery provides lower rates of complications and shorter hospitalizations for patients with gastric GIST than open surgery.