Radiotherapy For Gastric Cancer Research Articles

Comparison of gastric-cancer radiotherapy performed with volumetric modulated arc therapy or single-field uniform-dose proton therapy

Background: Proton-beam therapy of large abdominal cancers has been questioned due to the large variations in tissue density in the abdomen. The aim of this study was to evaluate the importance of these variations for the dose distributions produced in adjuvant radiotherapy of gastric cancer (GC), implemented with photon-based volumetric modulated arc therapy (VMAT) or with proton-beam single-field uniform-dose (SFUD) method.Material and methods: Eight GC patients were included in this study. For each patient, a VMAT- and an SFUD-plan were created. The prescription dose was 45 Gy (IsoE) given in 25 fractions. The plans were prepared on the original CT studies and the doses were thereafter recalculated on two modified CT studies (one with extra water filling and the other with expanded abdominal air-cavity volumes).Results: Compared to the original VMAT plans, the SFUD plans resulted in reduced median values for the V18 of the left kidney (26%), the liver mean dose (14.8 Gy (IsoE)) and the maximum dose given to the spinal cord (26.6 Gy (IsoE)). However, the PTV coverage decreased when the SFUD plans were recalculated on CT sets with extra air- (86%) and water-filling (87%). The added water filling only led to minor dosimetric changes for the OARs, but the extra air caused significant increases of the median values of V18 for the right and left kidneys (10% and 12%, respectively) and of V10 for the liver (12%). The density changes influenced the dose distributions in the VMAT plans to a minor extent.Conclusions: SFUD was found to be superior to VMAT for the plans prepared on the original CT sets. However, SFUD was inferior to VMAT for the modified CT sets.

Palliative radiotherapy for gastric cancer: a systematic review and meta-analysis.

Background/PurposeTo review the efficacy and toxicity of palliative radiotherapy (RT) for symptomatic locally advanced gastric cancer (GC) and to determine the optimal RT schedule for symptom palliation.MethodsWe searched MEDLINE and CENTRAL for eligible studies published from 1995 to 2015. Outcomes of interest were relief of bleeding, pain and obstruction.RESULTSSeven non-comparative observational studies were included. There were large variations in RT dose and fractionation. The pooled overall response rates for bleeding, pain and obstruction symptoms were 74%, 67% and 68% respectively. There was no difference in response rate of bleeding between regimens with high biological equivalent dose (BED) of = 39Gy versus regimens with low BED<39Gy regimens (p value =0.39). Grade 3 to 4 toxicities occurred in up to 15% of patients for patients treated with RT alone and up to 25% of patients treated with chemoradiotherapy. Health-related quality of life (HRQL) outcomes were not reported.ConclusionMore than two-thirds of patients receiving RT would have a clinical benefit. Low BED regimens appear to be adequate for symptom palliation. Toxicity rates appear acceptable for patients treated with RT alone. The optimal dose fractionation regimen for symptom palliation remains unclear. Prospective studies to determine the effects of palliative gastric RT on HRQL outcomes are warranted.

18-Fluorodeoxy-Glucose Positron Emission Tomography- Computed Tomography (18-FDG-PET/CT) for Gross Tumor Volume (GTV) Delineation in Gastric Cancer Radiotherapy

Purpose:Evaluation of the 18-fluorodeoxy-glucose positron emission tomography-computed tomography (18-FDG-PET/CT) for gross tumor volume (GTV) delineation in gastric cancer patients undergoing radiotherapy.Methods:In this study, 29 gastric cancer patients (17 unresectable and 7 inoperable) were initially enrolled for radical chemoradiotherapy (45Gy/25 fractions + chemotherapy based on 5 fluorouracil) or radiotherapy alone (45Gy/25 fractions) with planning based on the 18-FDG-PET/CT images. Five patients were excluded due to excess blood glucose levels (1), false-negative positron emission tomography (1) and distant metastases revealed by 18-FDG-PET/CT (3). The analysis involved measurement of metabolic tumor volumes (MTVs) performed on PET/CT workstations. Different threshold levels of the standardized uptake value (SUV) and liver uptake were set to obtain MTVs. Secondly, GTVPET values were derived manually using the positron emission tomography (PET) dataset blinded to the computed tomography (CT) data. Subsequently, GTVCT values were delineated using a radiotherapy planning system based on the CT scans blinded to the PET data. The referenced GTVCT values were correlated with the GTVPET and were compared with a conformality index (CI).Results:The mean CI was 0.52 (range, 0.12-0.85). In 13/24 patients (54%), the GTVPET was larger than GTVCT, and in the remainder, GTVPET was smaller. Moreover, the cranio-caudal diameter of GTVPET in 16 cases (64%) was larger than that of GTVCT, smaller in 7 cases (29%), and unchanged in one case. Manual PET delineation (GTVPET) achieved the best correlation with GTVCT (Pearson correlation = 0.76, p <0.0001). Among the analyzed MTVs, a statistically significant correlation with GTVCT was revealed for MTV10%SUVmax (r = 0.63; p = 0.0014), MTVliv (r = 0.60; p = 0.0021), MTVSUV2.5 (r = 0.54; p = 0.0063); MTV20%SUVmax (r = 0.44; p = 0.0344); MTV30%SUVmax (r = 0.44; p = 0.0373).Conclusion:18-FDG-PET/CT in gastric cancer radiotherapy planning may affect the GTV delineation.

253P The role of MiR-221 in regulating gastric cancer radiation sensitivity

253P The role of MiR-221 in regulating gastric cancer radiation sensitivity

In Vivo Magnetic Resonance and Fluorescence Dual-Modality Imaging of Tumor Angiogenesis in Rats Using GEBP11 Peptide Targeted Magnetic Nanoparticles.

Angiogenesis is an essential process for tumor progression. Tumor vasculature-targeting peptides have shown great potential for use in cancer imaging and therapy. Our previous studies have shown that GEBP11, a novel vasculature-specific binding peptide that exhibits high affinity and specificity to tumor angiogenesis, is a promising candidate for the diagnosis and targeted radiotherapy of gastric cancer. In the present study, we developed a novel magnetic resonance and fluorescence (MR/Fluo) dual-modality imaging probe by covalently coupling 2,3-dimercaptosuccinnic acid-coated paramagnetic nanoparticles (DMSA-MNPs) and Cy5.5 to the GEBP11 peptide. The probe Cy5.5-GEBP11-DMSA-MNPs (CGD-MNPs), with a hydrodynamic diameter of 82.8 ± 6.5 nm, exhibited good imaging properties, high stability and little cytotoxicity. In vivo MR/Fluo imaging revealed that CGD-MNPs were successfully applied to visualize tumor angiogenesis in SGC-7901 xenograft mouse models. Prussian blue and CD31 immunohistochemical staining confirmed that CGD-MNPs co-localized with tumor blood vessels. In conclusion, CGD-MNPs are promising candidates for use as MR and fluorescence imaging probes for visualizing gastric cancer angiogenesis in vivo.

CHK1 expression in Gastric Cancer is modulated by p53 and RB1/E2F1: implications in chemo/radiotherapy response.

Radiation has a limited but relevant role in the adjuvant therapy of gastric cancer (GC) patients. Since Chk1 plays a critical function in cellular response to genotoxic agents, we aimed to analyze the role of Chk1 in GC as a biomarker for radiotherapy resistance. We analyzed Chk1 expression in AGS and MKN45 human GC cell lines by RT-QPCR and WB and in a small cohort of human patient’s samples. We demonstrated that Chk1 overexpression specifically increases resistance to radiation in GC cells. Accordingly, abrogation of Chk1 activity with UCN-01 and its expression with shChk1 increased sensitivity to bleomycin and radiation. Furthermore, when we assessed Chk1 expression in human samples, we found a correlation between nuclear Chk1 accumulation and a decrease in progression free survival. Moreover, using a luciferase assay we found that Chk1’s expression is controlled by p53 and RB/E2F1 at the transcriptional level. Additionally, we present preliminary data suggesting a posttranscriptional regulation mechanism, involving miR-195 and miR-503, which are inversely correlated with expression of Chk1 in radioresistant cells. In conclusion, Chk1/microRNA axis is involved in resistance to radiation in GC, and suggests Chk1 as a potential tool for optimal stratification of patients susceptible to receive adjuvant radiotherapy after surgery.

Radiation-induced injury of the exocrine pancreas after chemoradiotherapy for gastric cancer

Background and purposeThe pancreas is located almost entirely within the treatment area for radiotherapy of gastric cancer. The aim of this study was to analyze radiation-induced injury of the exocrine pancreas. Material and methodsThe study included 127 gastric cancer patients, who underwent preoperative or postoperative chemoradiotherapy. A total dose of 45Gy was given in 25 fractions. Concurrent chemotherapy was 5-fluorouracil-based. Lipase and α-amylase were assayed before, during and after treatment. ResultsLipase and α-amylase deficiencies were found in 48.2% and 19.7% of patients, respectively. In the univariant analysis, age and pretreatment α-amylase and lipase activities influenced on risk of injury of the exocrine pancreas (p<0.05). Younger patients (<65years) had a lower risk of hypoamylasemia than older patients. The probability of insufficiency was lower than 0.2 for patients with pretreatment α-amylase and lipase activities above 50U/L and 55U/L, respectively. The multivariate analyses of the time to hypolipasemia showed that only pretreatment lipase activity was significant. ConclusionsGastric cancer patients have an increased risk of exocrine pancreatic insufficiency after chemoradiotherapy. Thus, the pancreas should be regarded as an OAR. Measuring lipase activity should be the standard for assessing radiation-induced pancreatic injury.

A new approach to delineating lymph node target volumes for post-operative radiotherapy in gastric cancer: A phase II trial

PurposeIn the context of gastric cancer, lymph node target volume delineation for post-operative radiotherapy is currently built on the traditional system of dividing the stomach and 2-D treatment methods. Here, we have proposed a new delineation approach with irradiation indications for lymph node stations. Its safety and efficacy were evaluated in a phase II clinical trial. Materials and methodsFifty-four gastric cancer patients with D2 lymph node dissection received 2 cycles of FOLFOX4. They subsequently received concurrent chemoradiotherapy (45Gy at 1.8Gy per fraction, 5 fractions per week for 5weeks) with a 5-fluorouracil/leucovorin regimen, followed by 4 additional FOLFOX4 cycles. The target volume included the remnant stomach, anastomosis site, tumor bed, and regional lymph nodes selected through our new approach by taking gastric arteries as references. ResultsThe most common grade 3–4 adverse event was neutropenia (14.8%). Neutropenia, anemia, and nausea were common grade 1–2 toxicities. No treatment-related deaths occurred during treatment. The 3-year overall, disease-free, and locoregional recurrence-free survival rates were 81.6%, 70.2%, and 91.1%, respectively. Eight patients developed peritoneal or distant metastases. ConclusionsUsing our new approach and irradiation indications, delineation of the target volume of post-operative lymph node stations was feasible and well tolerated after D2 resection in patients with gastric cancer.

Synergistic Effect of Simvastatin Plus Radiation in Gastric Cancer and Colorectal Cancer: Implications of BIRC5 and Connective Tissue Growth Factor

We investigated the synergistic effect of simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor plus radiation therapy, on the proliferation and survival of gastric cancer (GC) and colorectal cancer (CRC) cells. We also studied several genes involved in the simvastatin/radiation-induced effects. Gastric cancer (AGS, SNU601, MKN1, and MKN28) and CRC (CoLo320, SW48, HT29, and HCT8) cell lines were treated with 0.2 μM simvastatin alone, or in combination with 0 to 4 Gy of radiation, and subjected to clonogenic survival and proliferation assays in vitro. To assess the molecular mechanism of the combination treatment, we performed microarray analysis, immunoblot assays, small interfering RNA knockdown experiments, and plasmid rescue assays. The antitumoral effects of simvastatin and radiation were evaluated in vivo using xenograft models. The combination therapy of simvastatin plus radiation inhibited basal clonogenic survival and proliferation of GC and CRC cells in vitro. Simvastatin suppressed the expression of BIRC5 and CTGF genes in these cancer cells. In vivo, the combined treatment with simvastatin and radiation significantly reduced the growth of xenograft tumors compared with treatment with radiation alone. We suggest that simvastatin has a synergistic effect with radiation on GC and CRC through the induction of apoptosis, which may be mediated by a simultaneous inhibition of BIRC5 and CTGF expression. A clinical trial of simvastatin in combination with radiation in patients with GC or CRC is warranted.

Synergistic effect of simvastatin plus radiation in gastric cancer and colorectal cancer: Implications of BIRC5 and connective tissue growth factor.

e14588 Background: In this study, we investigated the synergistic effect of simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor plus radiation therapy, on the proliferation and...

Four-dimensional CT-based evaluation of intrafractional and interfractional anastomosis motion during postoperative radiotherapy in gastric cancer : a prospective study

Objective To study the intrafractional and interfractional anastomosis motion during postoperative adjuvant radiotherapy in gastric cancer by four-dimensional CT (4DCT) . Methods Eight patients with locally advanced gastric cancer who underwent Billroth I gastrectomy and postoperative radiotherapy were enrolled in this study and prospective analysis was performed. A total of four 4DCT, including simulation and repeating during radiation, were performed during free breathing and dietary restriction. The implanted anastomotic nail was used as the observational subject, and the intrafractional and interfractional anastomosis motion was evaluated in the right-left (RL) , anterior-posterior (AP) , and superior-inferior (SI) directions. The relationship between the volume change in remnant stomach and interfractional anastomosis motion was analyzed. The differences within and between groups were analyzed by paired t test and one-way ANOVA, respectively. Results The intrafractional anastomosis motion was (2.4±2.3) mm, (2.1±2.0) mm, and (5.6±4.0) mm in RL, AP, and SI directions, respectively, and the motion in SI direction was significantly greater than that in RL and AP directions (P=0.000 and 0.000). The interfractional anastomosis motion was (6.1±6.6) mm, (3.3±3.0) mm, and (4.8±4.3) mm in RL, AP, and SI directions, respectively, with no significant differences between different directions (P=0.064,0.156,0.161). In RL direction, the interfractional anastomosis motion was significantly greater than the intrafractional anastomosis motion (P=0.018). The internal margins accounting for respiration related displacement and interfractional variability were 24.2 mm, 10.3 mm, and 18.3 mm in RL, AP and SI directions, respectively. Conclusions The intrafractional and interfractional anastomosis motion should be considered during postoperative adjuvant radiotherapy in gastric cancer patients who have undergone Billroth I gastrectomy. The internal margins required for anastomosis in RL, AP and SI directions are 24.2mm, 10.3 mm and 18.3 mm, respectively. Key words: Tomography, X - ray computed, four - dimensional; Intrafractional displacement; Interfractional displacement; Gastric neoplasms/postoperative radiotherapy

Influence of interfraction motion on margins for radiotherapy of gastric cancer.

The aim of this study was to evaluate interfraction uncertainties using kilovoltage (kV) radiographs for patients with gastric cancer during chemoradiotherapy and to calculate the planning target volume (PTV) margins. 1284 measurements of set-up errors were analysed for treated patients. The measurements of craniocaudal (axis y), laterolateral (axis x) and anteroposterior (axis z) shifts in kV radiographs were performed. Interfraction clinical target volume (CTV)-PTV margins for all directions were calculated using the van Herk formula. The main shift for the y-axis was 0.7 mm [standard deviation (SD), ±7.6], for the x-axis was 0.4 mm (SD, ±3.7) and for the z-axis was 0.6 mm (SD, ±3.5). The CTV-PTV margin in the x, y and z directions was 8.3, 15.5 and 8.0 mm, respectively. We observed that the interfractional motion for patients increased approximately 0.0034 cm along the x direction with each subsequent fraction, whereas a 0.0058-cm reduction in length along the y-axis was observed. No time effects for the z direction were noticed. According to our experience, a PTV margin of 9 mm along the x-axis, 16 mm along the y-axis and 8 mm along the z direction should be considered in the absence of image-guided radiotherapy. This knowledge concerning PTV set-up margins could be particularly useful for centres without a kV on-board imaging system.

Increased Survival Associated With Postoperative Radiation in Gastric Cancer Before and After MAGIC Trial: A Population-Based Study

Increased Survival Associated With Postoperative Radiation in Gastric Cancer Before and After MAGIC Trial: A Population-Based Study

Phase I study of postoperative radiotherapy combined with capecitabine for gastric cancer

To determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of capecitabine combined with postoperative radiotherapy for gastric cancer. We enrolled patients with any T stage and node-positive gastroesophageal or gastric adenocarcinoma after complete resection with negative margins (R0) or microscopic (R1) or macroscopic (R2) resection. Intensity modulated radiotherapy (IMRT) using a five-to-seven-field, coplanar, sliding window technique was delivered to the tumor bed (T4b), anastomosis site, duodenal stump and regional lymph nodes (LNs) to a total dose of 45 Gy (1.8 Gy/fraction, 5 d/wk). Patients with R1 or R2 resection received 10.8 Gy as a boost. Capecitabine was administered twice daily on every radiotherapy treatment day in a dose-escalation schedule (mg/m²) of 625 (level I, n = 6), 700 (level II, n = 6), 800 (level III, n = 6), 900 (level IV, n = 0) and 1000 (level V, n = 0). DLT was defined as grade 4 leukopenia or neutropenia, grade 3-4 thrombocytopenia or anemia and grade 3-4 non-hematological toxicity. Between October 2007 and August 2009, 18 patients (12 men, 6 women; median age, 54 years) were enrolled in the study. The median number of positive LNs was 6, and total number of resected LNs was 19. Twelve patients underwent R0 resection (66.7%). Fifteen patients received adjuvant chemotherapy under the leucovorin, fluorouracil and oxaliplatin (FOLFOX4) regimen. Six patients each were enrolled at dose levels I, II and III. Grade 1-3 leukopenia (16 patients, 88.9%), anorexia (15, 83.3%) and nausea (15, 83.3%) were the most common toxicities. Grade 3 anorexia/nausea and grade 4 vomiting occurred in one level-I patient. Grade 3 anorexia and nausea occurred in one level-II patient. One level-III patient developed grade 4 neutropenia, while another developed grade 3 radiation esophagitis. No abnormal liver or renal function examinations were observed. Three patients did not finish chemoradiotherapy because of DLTs and two without DLTs received sequential boosts (total dose, 55.8 Gy). The MTD of capecitabine was 800 mg/m² twice daily concurrent with IMRT for gastric cancer after surgery. The DLTs were anorexia/nausea, vomiting, neutropenia and radiation esophagitis.

The use of fiducial markers in image‐guided radiotherapy for gastric cancer

The use of fiducial markers (FM) in image-guided radiotherapy (IGRT) to increase treatment precision is emerging for upper gastrointestinal malignancies. To our knowledge there is no data beyond technical reports for the use of FMs in IGRT for gastric cancers in the current literature. We report a case of an 89-year old gentleman with localised gastric cancer who was deemed unfit for surgery and chemotherapy. He had FMs inserted endoscopically around the tumour via ultrasound guidance and received radiotherapy with a high-dose palliative intent via a two-phase technique to 54 Gy in 30 fractions with IGRT. The use of FMs allowed confidence in tumour delineation and together with IGRT enabled precise and safe delivery of a higher dose. The patient tolerated the treatment without significant toxicity and had no evidence of residual or recurrent tumour 12 months following radiotherapy. The use of FMs with IGRT in upper gastrointestinal malignancies warrants further collaborative studies.

Targeted radiotherapy with tumor vascular homing trimeric GEBP11 peptide evaluated by multimodality imaging for gastric cancer

Targeted radiopharmaceutical is an effective treatment for solid tumors. By labeling with radionuclides, targeting peptide could achieve both noninvasive diagnosis and targeted radionuclide therapy. In order to evaluate the potential applicability of GEBP11 peptides in diagnosis and radiotherapy of gastric cancer, in this study, iodine 131 labeled GEBP11 peptides, including a novel bifid PEGlylated GEBP11 trimer and its corresponding monomer, were developed. The clinical potential of GEBP11 peptides, such as tumor binding affinity and antitumor efficacy was demonstrated and assessed with multimodality imaging methods. Cerenkov and SPECT imaging showed higher tumor uptake for 131I-2PEG-(GEBP11)3 (P<0.05, day 1; P<0.01, day 2; vs. monomer). Biodistribution studies indicated higher tumor accumulation and better T/NT of 131I-2PEG-(GEBP11)3. Bioluminescence imaging exhibited a significant tumor growth suppression in 131I-2PEG-(GEBP11)3 treated group (P<0.001 vs. control; P<0.01 vs. monomer). After treatment with 131I-2PEG-(GEBP11)3, the tumor volume and vasculature decreased significantly, and the survival time was prolonged to 75.5days. Meanwhile, no significant hepatic or renal toxicity was observed with 131I-2PEG-(GEBP11)3 administered. In conclusion, 131I-2PEG-(GEBP11)3 could be a promising candidate for peptide-based targeting therapy of gastric cancer. 2PEG-(GEBP11)3 might be a potential drug delivery vehicle for the antiangiogenic therapy of gastric cancer.

Adjuvant Treatment for Gastric Cancer: Chemotherapy Versus Radiation

Gastric cancer is among the leading causes of cancer death worldwide. Surgery is the only curative modality, but mortality remains high because a significant number of patients have recurrence after complete surgical resection. Chemotherapy, radiation, and chemoradiotherapy have all been studied in an attempt to reduce the risk for relapse and improve survival. There is no globally accepted standard of care for resectable gastric cancer, and treatment strategies vary across the world. Postoperative chemoradiation with 5-fluorouracil/leucovorin is most commonly practiced in the United States; however, recent clinical trials from Asia have shown benefit of adjuvant chemotherapy alone and have questioned the role of radiation. In this review, we examine the current literature on adjuvant treatment of gastric cancer and discuss the roles of radiation and chemotherapy, particularly in light of these new data and their applicability to the Western population. We highlight some of the ongoing and planned clinical trials in resectable gastric cancer and identify future directions as well as areas where further research is needed.

Radiotherapy for gastric cancer: a systematic review and meta-analysis

There have been many trials trying to prove the benefit of radiotherapy for gastric cancer; however, the results were either inclusive or controversial. The purpose of the study was to elucidate the effect of radiotherapy on gastric cancer delivered as perioperative or palliative treatment. We conducted systematic searches for trials exploring the effect of radiotherapy on gastric cancer. In the subgroup of patients receiving preoperative radiotherapy for gastric cancer, a significant benefit was found on 10-year overall survival with a hazard ratio (HR) of 0.75 (95% confidence interval (CI), 0.61 to 0.91); however, the benefit on 5-year overall survival was not proven (HR, 0.68; 95%CI, 0.45 to 1.01). There are also no significant differences in resection rate and radical resection rate between group of patients receiving radiotherapy and control group with a relative risk (RR) of 1.06 (95%CI, 0.99 to 1.13) and 1.12 (95%CI 0.93 to 1.36), respectively. In the subgroup of patients receiving postoperative radiotherapy for gastric cancer, survival benefits were found on 3- and 5-year progression-free survival with HR of 0.69 (95%CI, 0.53 to 0.90) and HR of 0.70 (95%CI, 0.61 to 0.80), respectively. Survival benefits of adjuvant radiotherapy on 3- and 5-year progression-free survival were also found; nonetheless, there was no evidence of significant difference in 3-year overall survival (HR, 0.70; 95%CI, 0.61 to 1.01). The effect of radiotherapy on 5-year overall survival was also quite controversial. In short, gastric cancer patients could benefit from radiotherapy both in the form of preoperative radiotherapy and postoperative radiotherapy.

Planning comparison between standard and conformal 3D techniques in post-operative radiotherapy of gastric cancer: a systematic review

The objective of this study was to establish the impact of three-dimensional conformal radiotherapy (3D-CRT) technique in post-operative radiotherapy of gastric cancer. A bibliographical research was performed using the PubMed. On the database, Search was carried out using Medical Subject Heading (MeSH) database; the algorithm for search was ''Radiotherapy" (MeSH) AND ''Stomach Neoplasms" (MeSH). Only planning comparative studies on conformal techniques vs standard techniques in post-operative radiotherapy of gastric cancer were included in the review process. We identified 185 papers, five of them fulfilling the inclusion criteria. A great inhomogeneity was observed regarding the analysed dosimetric end points. Three of the five studies reported a benefit in favour of 3D-CRT for target irradiation despite a minimal advantage in most cases. The liver was better spared from irradiation by the traditional technique in all studies. No univocal result was obtained for the right kidney: the traditional technique performed better in two studies, 3D-CRT yielded better results in two others, whereas in the fifth study, each technique was either better or worse according to the different considered end point. 3D-CRT, however, allowed for better sparing of the left kidney in four studies. There is no absolute reason to prefer 3D-CRT with multiple beams in every patient. It may be preferable to choose the technique based on individual patient characteristics. Because there is no proof of superiority for 3D-CRT, there is no absolute reason to exclude patients who are treated in centres equipped with only the two-dimensional technique from the potential benefit of post-operative chemoradiation.

Single-arc volumetric-modulated arc therapy (sVMAT) as adjuvant treatment for gastric cancer: Dosimetric comparisons with three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT)

To compare the dosimetric differences between the single-arc volumetric-modulated arc therapy (sVMAT), 3-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for gastric cancer as adjuvant radiotherapy. Twelve patients were retrospectively analyzed. In each patient's case, the parameters were compared based on the dose-volume histogram (DVH) of the sVMAT, 3D-CRT, and IMRT plans, respectively. Three techniques showed similar target dose coverage. The maximum and mean doses of the target were significantly higher in the sVMAT plans than that in 3D-CRT plans and in the 3D-CRT/IMRT plans, respectively, but these differences were clinically acceptable. The IMRT and sVMAT plans successfully achieved better target dose conformity, reduced the V20/30, and mean dose of the left kidney, as well as the V20/30 of the liver, compared with the 3D-CRT plans. And the sVMAT technique reduced the V20 of the liver much significantly. Although the maximum dose of the spinal cord were much higher in the IMRT and sVMAT plans, respectively (mean 36.4 vs 39.5 and 40.6Gy), these data were still under the constraints. Not much difference was found in the analysis of the parameters of the right kidney, intestine, and heart. The IMRT and sVMAT plans achieved similar dose distribution to the target, but superior to the 3D-CRT plans, in adjuvant radiotherapy for gastric cancer. The sVMAT technique improved the dose sparings of the left kidney and liver, compared with the 3D-CRT technique, but showed few dosimetric advantages over the IMRT technique. Studies are warranted to evaluate the clinical benefits of the VMAT treatment for patients with gastric cancer after surgery in the future.