Intensity-modulated Volumetric Arc Therapy Research Articles

Comparative analysis of simultaneous integrated boost and sequential boost radiotherapy in node-positive cervical cancer: dosimetric and radiobiological considerations.

For locally advanced cervical cancer, the standard therapeutic approach involves concomitant chemoradiation therapy, supplemented by a brachytherapy boost. Moreover, an external beam radiotherapy (RT) boost should be considered for treating gross lymph node (LN) volumes. Two boost approaches exist with Volumetric Intensity Modulated Arc Therapy (VMAT): Sequential (SEQ) and Simultaneous Integrated Boost (SIB). This study undertakes a comprehensive dosimetric and radiobiological comparison between these two boost strategies. The study encompassed ten patients who underwent RT for cervical cancer with node-positive disease. Two sets of treatment plans were generated for each patient: SIB-VMAT and SEQ-VMAT. Dosimetric as well as radiobiological parameters including tumour control probability (TCP) and normal tissue complication probability (NTCP) were compared. Both techniques were analyzed for two different levels of LN involvement - only pelvic LNs and pelvic with para-aortic LNs. Statistical analysis was performed using SPSS software version 25.0. SIB-VMAT exhibited superior target coverage, yielding improved doses to the planning target volume (PTV) and gross tumour volume (GTV). Notably, SIB-VMAT plans displayed markedly superior dose conformity. While SEQ-VMAT displayed favorable organ sparing for femoral heads, SIB-VMAT appeared as the more efficient approach for mitigating bladder and bowel doses. TCP was significantly higher with SIB-VMAT, suggesting a higher likelihood of successful tumour control. Conversely, no statistically significant difference in NTCP was observed between the two techniques. This study's findings underscore the advantages of SIB-VMAT over SEQ-VMAT in terms of improved target coverage, dose conformity, and tumour control probability. In particular, SIB-VMAT demonstrated potential benefits for cases involving para-aortic nodes. It is concluded that SIB-VMAT should be the preferred approach in all cases of locally advanced cervical cancer.

Could a low-dose definitive radiation therapy be the optimal treatment for choroidal hemangioma?

PurposeTo determine the efficacy of low-dose intensity-modulated radiation therapy (IMRT)/volumetric intensity-modulated arc therapy (VMAT) in the treatment of symptomatic choroidal hemangioma (CH). Materials and methodsFifty-three consecutive patients with CH were retrospectively reviewed. All the patients underwent IMRT/VMAT as a unique treatment. Resolution of subretinal fluid (SRF), improvement of best-corrected visual acuity (BCVA), and reduction in tumor thickness were compared before and after radiotherapy. ResultsAfter definitive radiotherapy, 100 % of SRF and 76.7 % of exudative retinal detachment were resolved. 56.6 % of BCVA improvement in more than two lines was observed. The mean best-corrected visual acuity was 20/280 (range, 20/1200–20/40) at diagnosis and 20/100 (range, 20/1200–20/20) after treatment. The mean tumor thickness decreased significantly from 3.8 mm initially to 1.2 mm after treatment (p < 0.01). 66.0 % of patients were delivered with 21.6 Gy (range, 21.6–42 Gy), 84.9 % of fractional dose was 1.8 Gy (range, 1.8–2 Gy). No radiation-induced keratitis, retinopathy, or optic neuropathy were observed. Initial vision (p = 0.042), duration time of vision (p = 0.004), and tumor thickness (p = 0.049) were prognostic factors for vision recovery. ConclusionLow-dose IMRT/VMAT could effectively induce involution of the CH, with reduction of subretinal fluid and relief of damage to the neurosensory retina, which is an effective treatment mode for CH.

Stereotactic body radiotherapy with volumetric intensity-modulated arc therapy and flattening filter-free beams: dosimetric considerations.

The present study comparatively evaluates the impact of energy-matched flattening filter-free (FFF) photon beams with different energy levels on the physical-dosimetric quality of lung and liver stereotactic body radiotherapy (SBRT) treatment plans. For this purpose, 54different lung and liver lesions from 44patients who had already received SBRT combined with volumetric modulated arc therapy (VMAT) were included in this retrospective planning study. Planning computed tomography scans already available were used for the renewed planning with 6MV, 6MV-FFF, 10MV, and 10MV-FFF under constant planning objectives. The treatment delivery data, dosimetric distributions, and dose-volume histograms as well as parameters such as the conformity index and gradient indices were the basis for the evaluation and comparison of treatment plans. Asignificant reduction of beam-on time (BOT) was achieved due to the high dose rates of FFF beams. In addition, we showed that for FFF beams compared to flattened beams of the same energy level, smaller planning target volumes (PTV) require fewer monitor units (MU) than larger PTVs. An equal to slightly superior target volume coverage and sparing of healthy tissue as well as organs at risk in both lung and liver lesions were found. Significant differences were seen mainly in the medium to lower dose range. We found that FFF beams together with VMAT represent an excellent combination for SBRT of lung or liver lesions with shortest BOT for 10MV-FFF but significant dose savings for 6MV-FFF in lung lesions.

Neoadjuvant Chemoradiotherapy vs. Neoadjuvant Chemotherapy for the Treatment of Esophageal Squamous Cell Carcinoma: A Stabilized Inverse Probability of Treatment Weighting Analysis

<h3>Purpose/Objective(s)</h3> To compare long-term survival and safety of neoadjuvant chemotherapy (nCT) and neoadjuvant chemoradiotherapy (nCRT) in patients with esophageal squamous cell carcinoma (ESCC). <h3>Materials/Methods</h3> In 2012ཞ2020, patients diagnosed with ESCC were documented in the National Cancer Center database. as follows: 1) 18-75 years old; 2) histologically proven as stage T1-2N+M0 or T3-4N0-3M0; 3) histologic subtype was ESCC; 4) R0 resection; 5) radiotherapy dose ≥ 40Gy for primary tumor and metastatic lymph nodes. Stabilized inverse probability of treatment weighting (sIPTW) were used to minimize bias due to potential confounding factors, including sex, age, tumor location, tumor length, TNM clinical stage. The outcome included overall survival (OS), disease-free survival (DFS), pathological complete responses (pCR), and perioperative mortality and morbidity. <h3>Results</h3> A total of 419 patients (male,8 7.1%; mean age, 59.7 years) were enrolled to the nCRT group (n=158) or the nCT group (n=261). median follow-up time was 26 (7ཞ113) months in the nCRT group and 24 (7ཞ101) months in the nCT group, respectively. The chemotherapy regimen of nCT group was paclitaxel combined with platinum every 21 days with a median cycle of 3 (1ཞ4). In nCRT group, paclitaxel and platinum was performed weekly with a median of 3 cycles. The median radiotherapy dose for primary tumor and metastatic lymph nodes of 45Gy (40ཞ50.4Gy), 1.8ཞ2.14Gy/fraction, was delivered by intensity-modulated radiotherapy (IMRT) or volumetric intensity modulated arc therapy (VMAT). nCRT significantly improved the pCR rate as compared to nCT group (28.5% vs 9.2%, <i>P</i><0.001). The 1, 3 and 5-year OS in the nCRT and nCT group were 96.2% vs 98.1%, 78.4% vs 70.3% and 67.9% vs 53.3%, respectively (<i>P</i> =0.140). The incidence of anastomotic leak was in 13 of 158 patients (8.2%) in the nCRT group and 4 of 261 patients (1.5%) in the nCT group (<i>P</i> The total postoperative complications rate was 10.1% in the nCRT group (16 of 158) and 7.7% in the nCT group (20 of 261). After sIPTW, the clinical and demographic characteristics of the two groups were well balanced. The nCRT group was associated with a better OS than the nCT group (96.7% vs 97.6% at 1 year; 81.0% vs 69.2% at 3 years and 72.6% vs 48.2% 5 years, <i>P</i>=0.04). <h3>Conclusion</h3> Compared to nCT, paclitaxel and platinum-based nCRT using IMRT or VMAT technique improved OS in ESCC patients. Prospective head-to-head comparison and novel strategies with advanced drug therapy and radiotherapy technique to improve the outcomes in resectable ESCC are warranted.

Advancements in the radiooncological treatment of high-risk prostate cancer: a quarter century of achievements.

BackgroundThe aim of the study was to evaluate the development of treatment of primary high-risk prostate cancer in regards to biochemical no evidence of disease (bNED), acute and late gastrointestinal (GI) and genitourinary (GU) side effects.Patients and methodsPrimary high-risk prostate cancer patients treated between 1994 and 2016 were included. Applied doses ranged from 60 to 80 Gy, with a dose of 1.8 or 2 Gy per fraction. Techniques were either 3D conformal or intensity modulated radiotherapy and volumetric intensity modulated arc therapy.Results142 patients were treated with doses up to 70 Gy (median dose 66 Gy; 66 Gy group), 282 with doses between 70 and 76 Gy (median dose 74 Gy; 74 Gy group), and 141 with doses >76 Gy (median dose 78 Gy; 78 Gy group). The median follow-up was 48 months. The bNED rates were 50% after 5 years and 44% after 9 years in the 66 Gy group; 65% and 54%, respectively, in the 74 Gy group; and 83% and 66%, respectively, in the 78 Gy group (p = 0.03 vs. 74 Gy and p < 0.0001 vs. 66 Gy). We found a higher rate of acute GI side effects in the 78 Gy group compared to the other groups, but not in maximum acute GU side effects and late maximum GI and GU effects.ConclusionsHigh-risk prostate cancer patients treated with doses of 78 Gy had significantly better bNED rates. Compared to the historical 66 Gy group, 50% more patients achieved bNED after a follow-up of 9 years.

Carbon Ion Beam Boost Irradiation in Malignant Tumors of the Nasal Vestibule and the Anterior Nasal Cavity as an Organ-Preserving Therapy.

BackgroundSurgery and radiotherapy are current therapeutic options for malignant tumors involving the nasal vestibule. Depending on the location, organ-preserving resection is not always possible, even for small tumors. Definitive radiotherapy is an alternative as an organ-preserving procedure. Carbon ion beam radiotherapy offers highly conformal dose distributions and more complex biological radiation effects eventually resulting in optimized normal tissue sparing and improved outcome. The aim of the current study was to analyze toxicity, local control (LC), and organ preserving survival (OPS) after irradiation of carcinoma of the nasal vestibule with raster-scanned carbon ion radiotherapy boost (CIRT-B) combined with volumetric intensity modulated arc therapy (VMAT) with photons.MethodsBetween 12/2015 and 05/2021, 21 patients with malignant tumors involving the nasal vestibule were irradiated with CIRT-B combined with VMAT and retrospectively analyzed. Diagnosis was based on histologic findings. A total of 17 patients had squamous cell carcinoma (SCC) and 4 had other histologies. In this series, 10%, 67%, and 24% of patients had Wang stages 1, 2, and 3 tumors, respectively. Three patients had pathologic cervical nodes on MRI. The median CIRT-B dose was 24 Gy(RBE), while the median VMAT dose was 50 Gy. All patients with pathologic cervical nodes received simultaneously integrated boost with photons (SIB) up to a median dose of 62.5 Gy to the pathological lymph nodes. Eight patients received cisplatin chemotherapy. All patients received regular follow-up imaging after irradiation. Kaplan–Meier estimation was used for statistical assessment.ResultsThe median follow-up after irradiation was 18.9 months. There were no common toxicity criteria grade 5 or 4 adverse events. A total of 20 patients showed grade 3 adverse events mainly on skin and mucosa. All patients were alive at the end of follow-up. The median OPS after treatment was 56.5 months. The 6- and 24-month OPS were 100% and 83.3%, respectively. All local recurrences occurred within 12 months after radiotherapy. The median progression free survival (PFS) after treatment was 52.4 months. The 6-, 12-, and 24-month PFS rates were 95%, 83.6%, and 74.3%, respectively.ConclusionCIRT-B combined with VMAT in malignant tumors of the nasal vestibule is safe and feasible, results in high local control rates, and thus is a good option as organ-preserving therapy. No radiation-associated grade 4 or 5 acute or late AE was documented.

Predicting Response of Lung Cancer with Definitive Radiation Therapy: A Radiomics-Based Prediction Model

We hypothesize that radiomic features provide information for predicting early treatment response of lung cancer with definitive radiation therapy (RT). This study aims to develop and validate a radiomics-based model for predicting early treatment response of lung cancer with definitive radiation therapy (RT).From January 2018 to March 2020, 128 lung cancer patients with definitive radiation therapy (RT) had enrolled retrospectively in the study and randomly divided into training set (n = 90) and test set(n = 38). Based on the Response Evaluation Criteria in Solid Tumors1.1 (RECIST1.1), response of lung cancer with definitive radiation therapy (RT) was dichotomized that treatment was effective if tumor volume decreased over 30༅ at the first follow-up CT after definitive radiation therapy (RT). Radiomic features were extracted using an open-source software development tool from the Gross Tumor Volume (GTV) of planning CT images. Specifically, a total of 107 radiomics features are extracted that include the first-order statistic features, the second-order texture features, and 2D-3D shape-based features. To reduce the feature dimensionality, we used the RFE (Recursive Feature Elimination) method to filter the features and obtained 13 out of 107 features that are most effective for final classification. By analyzing the data and comparing the experimental validation, we employed Random Forest classifier for the response prediction.All patients received definitive radiation therapy (56-70Gy) and no operation. 36 patients received Intensity-modulated radiation therapy (IMRT) and 92 patients received Volumetric Intensity Modulated Arc Therapy (VMAT) (P = 0.951). 103 patients are men and 25 patients are women (P = 0.969). In addition to the five-fold cross-validation, we evaluated the classification results using the independent test set. The AUC for five-fold cross validation is 0.798, and the AUC for the independent test set is 0.771.This study demonstrated that radiomic model shows a good prediction value of early treatment response of lung cancer with definitive radiation therapy (RT). Radiomic features extracted from the Gross Tumor Volume (GTV) of planning CT images may predict response of radiation and might be helpful for individual treatments. The result still needs to be further validated by increasing the amount of data, especially prospective data.

P04.02 Three Definitions of Normal Lung Volumes for Predicting Radiation Pneumonitis in Advanced NSCLC Treated With Radical Chemoradiation Therapy

Chemoradiotherapy followed by durvalumab is the standard treatment for the patients with unresectable stage III non-small cell lung cancer (NSCLC), but Grade 2 or greater radiation pneumonitis (RP2) is a major obstacle of the use of following consolidative immunotherapy. Although several dosimetric parameters were found to be predictive of RP2, including mean lung dose (MLD) and the lung volume receiving ≥20 Gy (V20), very few researches have noted different definition of normal lung volume may affect the predictive value of the dosimetric parameters, especially in the curative-intent volumetric intensity modulated arc therapy (VMAT) planning, and limited data regarding the onset of RP2 in different time windows. The purpose of this study was to investigate associations between clinical and three definitions of normal lung volumes and RP2. We retrospectively analyzed 117 stage III NSCLC patients treated with chemotherapy concurrent or sequential VMAT from January 2015 to May 2019 in Guangdong Lung Cancer Institute. Patients with palliative dose (<60 Gy), poor performance status (≥2) or <6 months follow-up were excluded. The incidence of radiation pneumonitis in lung cancer was counted every two weeks. Dosimetric parameters including MLD, V20 and the lung volume receiving ≥5 Gy (V5) were calculated based on three definition of normal lung which excluding GTV (Lung-GTV), CTV (Lung-GTV) or PTV (Lung-GTV) from the total bilateral lung volume. The different RP2 prediction ability was assessed by the areas under the curve (AUC) of receiver operating characteristic (ROC) curves. Clinical and dosimetric factors regarding radiation pneumonitis were evaluated using repeated analysis of variance. The median age of patients was 60 years and median follow-up was 1.4 years. 79(67.5%) patients received concurrent cisplatin/etoposide (45,38.5%) or carboplatin/paclitaxel (28,23.9%) and 38(32.5%) patients received sequential carboplatin/paclitaxel (29,24.8%).Grade 2 or more radiation pneumonitis were developed in 31 (26.5%) patients. Of these, 18(58.1%) occurred within 12 weeks, 10(32.3%), 3(9.6)developed between 12 to 24 weeks and after 24 weeks respectively. There is significant heterogeneity in MLD, V20 among the various definition methods (all p<.05), average MLD, V20 were 16.3Gy,28.6%; 15.5Gy,27.4% and 14.3 Gy,25.6% when excluding GTV, CTV and PTV, respectively. The best RP2 prediction performance is found in MLD from Lung-GTV method (AUC = 0.688), which is significantly better (P = 0.002) than Lung-CTV method (AUC = 0.672) and Lung-CTV method (AUC = 0.654). RP2 most commonly developed within 12 weeks after radiotherapy. MLD from the GTV exclusion method may be more accurate in predicting clinically significant radiation pneumonitis while V5, V20 or any of the clinical factors are shows no statistical significance.

Linear accelerator-based stereotactic body radiation therapy in the treatment of oligometastatic disease.

The present study reports the clinical outcomes of hypofractionated stereotactic body radiation therapy (SBRT) for oligometastasis (OM) originating from various tumors. Between February 2012 and April 2017, 40 patients with unresectable OM were treated with SBRT. Of these patients, 92% showed a solitary nodal metastasis and the rest had up to three metastases. The dose prescription was 50 Gy in 10 fractions with three-dimensional conformal techniques or volumetric intensity-modulated arc therapy. Median follow-up was 14 months. Of the 40 patients, none showed local progression at the site of SBRT, but 20 patients showed tumor growth at distant sites during follow-up. The 2- and 3-year overall survival rates were 45.1 and 36.1%, respectively. The 2- and 3-year progression-free survival rates were 35.4 and 26.5%, respectively. The interval between diagnosis and detection of OM (<2 vs. >2 years) and primary tumor site (esophagus vs. others) emerged as significant variables affecting survival. Grade 3 subacute and grade 4 chronic toxicities were observed in 1 and 2 patients, respectively. SBRT of 50 Gy in 10 fractions for OM from various primary tumors was shown to lead to good clinical outcomes from the viewpoints of local control and toxicity frequency. However, additional studies are required to identify the patient groups likely to receive maximal benefits from such treatment.

Radiation-induced brain injury after a conventional dose of intensity-modulated radiotherapy for nasopharyngeal carcinoma: a case report and literature review*

Abstract A 61-year-old female nasopharyngeal carcinoma patient was admitted to the hospital with sudden cognitive dysfunction one month after Volumetric Intensity Modulated Arc Therapy (VMAT) conventional dose radiotherapy, and the initial diagnosis was radiation-induced brain injury (RBI). After comprehensive treatment with steroid hormones, the patient's condition rapidly improved. Typically, in nasopharyngeal carcinoma patients treated with VMAT, the incidence of RBI is extremely low when the temporal lobe dose is less than 65 Gy or 1% of the volume is less than 65 Gy. When this limit is exceeded, RBI may occur in varying degrees. However, in this case, even though the temporal lobe dose was under the prescribed limit, the patient still experienced RBI. The rare observations in this case can be used as a reference, and clinicians should seriously consider the possibility of RBI in similar cases.

Hippocampal sparing in stereotactic radiotherapy for brain metastases: To contour or not contour the hippocampus?

PurposeThe aim of our study was to evaluate hippocampal irradiation in patients treated with fractionated stereotactic brain radiotherapy. Patients and methodsRetrospective hippocampal dosimetric analysis performed on 22 patients with one to four brain metastases treated with fractionated stereotactic radiotherapy using volumetric intensity-modulated arc therapy. Original plans did not include hippocampus as avoidance structure in optimization criteria; hippocampus was retrospectively delineated on magnetic resonance coregistered with planning CT and using as reference the RTOG 0933 atlas. Hippocampus was defined both as a single and as pair organ. Constraints analysed were: Dmax<16Gy, D40%<7.3Gy, D100%=Dmin<9Gy. Assuming a α/β ratio of 2Gy, biologically equivalent dose in 2Gy fractions was calculated. Hippocampal-sparing plans were developed in cases where hippocampal constraints were not respected in the original plan. ResultsAmong constraints analysed Dmax and D40% have been exceeded in ten out of 22 cases. The constraints were not respected in patients with more than one metastatic lesion and in three patients with only one lesion. Considering all exceeded constraints values in non-hippocampal sparing plans, the 50% of them was respected after replanning. No significant differences were found among conformity and homogeneity index between non-hippocampal sparing and hippocampal sparing plans. ConclusionVolumetric intensity-modulated arc therapy hippocampal sparing plans significantly decreases dose to hippocampus assuring an equal target coverage and organs at risk avoiding.

Radiotherapy for Adult Medulloblastoma: Evaluation of Helical Tomotherapy, Volumetric Intensity Modulated Arc Therapy, and Three-Dimensional Conformal Radiotherapy and the Results of Helical Tomotherapy Therapy.

Introduction All adult medulloblastoma (AMB) patients should be treated with craniospinal irradiation (CSI) postoperatively. Because of the long irradiation range, multiple radiation fields must be designed for conventional radiotherapy technology. CSI can be completed in only one session with helical tomotherapy (HT). We evaluated the dose of HT, volumetric intensity modulated arc therapy (VMAT), and three-dimensional conformal radiotherapy (3D-CRT) of AMB and the results of 5 cases of AMB treated with HT. Methods Complete craniospinal and posterior cranial fossa irradiation with HT, VMAT, and 3D-CRT and dose evaluation were performed. And results of 5 cases of AMB treated with HT were evaluated. Results A large volume of tissue was exposed to low dose radiation in the organs at risk (OAR), while a small volume was exposed to high dose radiation with HT. The conformity and uniformity of the targets were good with HT and VMAT, and the volume of targets exposed to high dose with VMAT was larger than that of HT. The uniformity of 3D-CRT was also good, but the dose conformity was poor. The main toxicity was hematologic toxicity, without 4th-degree bone marrow suppression. There was 3rd-degree inhibition in the white blood cells, hemoglobin, and platelets. The three female patients suffered menstrual disorders during the course of radiation. Two female patients with heavy menstruation suffered 3rd-degree anemia inhibition, and 2 patients suffered amenorrhea after radiotherapy. Although menstrual cycle was normal, the third patient was not pregnant. Conclusion CSI with HT is convenient for clinical practice, and the side effects are mild. With good conformity and uniformity, VMAT can also be used for selection in CSI. For poor conformity, 3D-CRT should not be the priority selection for CSI. In female patients, the ovaries should be protected.

A Comparison of IMRT and VMAT Treatment Planning for Head and Neck Cancer With NTCP/TCP Analysis

Intensity-modulated radiation therapy (IMRT) and volumetric intensity-modulated arc therapy (VMAT) for HN cancers have been used with comparable coverage of planning target volumes (PTV). However, there is controversy over superiority of these techniques in management of HN cancers due to proximity to organs at risk (OAR), beam time, monitor units (MU) and integral dose. Using conventional dosimetric parameters conformity and homogeneity index (CI, HI), and biological indices NTCP/TCP, we evaluated VMAT and IMRT in their ability to provide superior coverage of PTV while sparing OAR. Fourteen consecutive HN cancer patients treated to the bilateral neck were planned with both IMRT and VMAT techniques in a commercial treatment planning system with 100% coverage to 95% PTV volume to a dose of 7000cGy. If OAR dose constraints were met for both VMAT and IMRT plans, a VMAT plan was preferred for treatment. The CI, HI, MU, gradient, as well as NTCP/TCP values were calculated. OAR studied include spinal cord, brachial plexus, bilateral parotids, constrictors, and larynx. Maximum doses for serial organs and mean doses for parallel organs were calculated for each OAR. NTCP model parameters were taken from QUANTEC and calculated for larynx, parotid, and spinal cord. TCP was modeled with published parameters based on a Poisson model with repopulation and sublethal damage. Statistical comparisons between VMAT and IMRT parameters were made using the paired t-test. The TCP values ranged 70-85% and were not significantly different (P>0.05) in IMRT compared to VMAT. NTCPs for the larynx and left/right parotid did not differ significantly between IMRT and VMAT plans. The PTV HI and CI were not significantly different between plans. Based on OAR coverage, six plans were treated with IMRT instead of VMAT. The OARs that were better spared in these six IMRT plans were constrictors (N=3), oral cavity (N=1), parotid (N=1) and brachial plexus (N=1). Significantly more MUs were used in IMRT plans than VMAT plans (average difference 733 MU, p<0.001). Maximum doses in VMAT plans were significantly greater than IMRT plans (mean max-dose difference 98cGy, p = 0.001). VMAT plans had an average maximum cord dose 1800cGy lower than IMRT plans (p < 0.001). IMRT delivered significantly lower mean dose to the oral cavity (mean dose difference 288cGy, p = 0.003) and middle/inferior constrictors (mean dose difference 121cGy, p = 0.02; 220cGy, p = 0.03, respectively). There was no significant difference between techniques in mean dose delivered to larynx or parotids or maximum dose delivered to the brachial plexus. IMRT and VMAT techniques generated comparable coverage of PTV and resulted in similar TCP. VMAT showed a significant reduction of MU and maximum dose delivered to spinal cord. Selection of techniques should be based on a more nuanced clinical decision rather than purely physical parameters.

Analysis of VMAT dosimetric verifications with different techniques

Objective To investigate the gamma (γ) passing rates for volumetric-modulated arc therapy (VMAT) dosimetric verification with different techniques. Methods A total of 12 VMAT plans for the treatment of different anatomical sites in cancer patients were chosen. The Octavius 4D system was used to measure the dose distributions in two different settings: the gantry was rotating (three-dimensional (3D) and 2D γ-analysis) and the gantry was fixed at 0°(2D γ-analysis). The γ passing rates were analyzed with 3%/3 mm and 2%/2 mm criteria, using the paired t test or Wilcoxon signed-rank test. The 2D γ passing rates for different irradiation methods were calculated. Results For the 3D and 2D dose distributions obtained at a rotating gantry angle as well as the 2D dose distribution obtained at zero gantry angle, the average γ passing rates were 96.03%, 96.98%, and 98.90% for 3%/3 mm (P= 0.227, P= 0.000, P= 0.003); 82.08%, 84.04%, and 90.90% for 2%/2 mm (P= 0.379, P= 0.000, P= 0.000). For the 2D dose distributions obtained with different irradiation methods, the average γ passing rate was 98.99% for 3%/3 mm and 93.68% for 2%/2 mm. Conclusions The VMAT dosimetric verification based on a 3D volumetric dosimeter at a rotating gantry position can be clinically useful for delivery quality assurance (QA), and can achieve the most reliable dose calculation for VMAT, which has more referential values. Key words: Volumetric intensity modulated arc therapy; Dosimetric verification; Octavius 4D system; γ passing rates

Health-related quality of life outcomes in a phase I/II study of stereotactic hypofractionated once-weekly radiation therapy (SHORT) for nonmetastatic prostate cancer.

126 Background: Stereotactic Radiation Therapy (SRT) for prostate cancer offers an opportunity to exploit the low alpha/beta ratio of prostate cancer. We present patient reported health-related Quality-of-life (HR-QoL) outcomes of an SRT schedule with once-weekly fractionation in an unselected cohort of non-metastatic prostate cancer. Methods: In a Phase I/II study 30 patients with non-metastatic prostate cancer (multiparametric MRI cT1-4N0, M0, Gleason 6-10, PSA &lt; = 60 ng/ml) were treated to a dose of 35Gy in 5 fractions delivered once a week (along with simultaneous elective nodal radiotherapy at 25Gy/5Fr to patients high-risk by NCCN criteria). Androgen deprivation therapy given to intermediate and high-risk patients. Treatments were planned using volumetric intensity modulated arc therapy. Quality of life was assessed using the EORTC QLQ C30 and PR25 questionnaires. HR-QoL parameters at baseline (before start of SRT) was compared to those at treatment completion and 3 months post-SRT. The raw QoL scores were converted to a scale of 0-100 by convention. A scale difference of 10 or higher was considered clinically meaningful. Results: All of the 30 recruited patients completed treatment and HR-QoL data were available at 3 time points for all patients. The ratio of low, intermediate and high risk patients was 1:9:20. SRT was well tolerated with no acute Grade 3 GI or GU symptoms by NCI CTC v4 (separately reported). Twenty one parameters were studies within the QLQ C30 and PR25 framework. At the end of treatment, only the urinary symptom score showed a clinically meaningful worsening (mean of 20/100 at baseline vs 34/100 at end of treatment, p &lt; 0.001). At 3 months, the urinary symptom score had returned close to baseline (26/100, p = 0.08). There was no clinically meaningful deterioration in the remaining HR-QoL parameters. Conclusions: Patient perception of function and symptoms with once-weekly SRT was good, with only a temporary worsening of the urinary symptom score, and subsequent recovery by 3 months. Compared to baseline scores, other QoL parameters did not show a clinically meaningful difference at end of treatment or at 3 months. Clinical trial information: CTRI/2016/02/006671.

Phase I/II study on stereotactic hypofractionated once-weekly radiation therapy (SHORT) for localized prostate cancer.

130 Background: The low α/β ratio of prostate cancer (PrCa) is well established. However, stereotactic hypofractionated radiotherapy (SRT) has been investigated primarily in highly selected patient populations with low-intermediate risk disease. We performed a clinical trial of SRT delivered in once-weekly fractions on an unselected cohort of patients with non-metastatic PrCa. Methods: In this Phase I/II study 30 patients with non-metastatic PrCa (multiparametric MRI cT1-4N0, M0, Gleason 6-10, PSA &lt; = 60 ng/ml) were treated with SRT to a prescription dose of 35Gy in 5 fractions delivered once a week (overall treatment time 29 days). Elective nodal RT at 25Gy/5Fr was delivered in patients high-risk by NCCN criteria, and androgen deprivation therapy given to intermediate and high-risk patients. SRT was planned using volumetric intensity modulated arc therapy (VMAT) or Helical Tomotherapy (HT) with pre-defined dose-criteria. The primary endpoint was acute toxicity NCI CTC v4, and secondary endpoints were biochemical control and late toxicity. Results: Thirty patients completed treatment per-protocol. Stage T3, Gleason 8-10, and PSA &gt; 10 was seen in 18 (60%), 7 (23%) and 24 (80%) respectively. Overall 20 (66.7%) were high-risk. Median of Mean PTV dose was 36Gy, and normal tissue constraints could be met in all patients (Table). Acute urinary toxicities (Gr 0: 1; Gr 1: 27; Gr 2: 1; Gr 3-4: 0) and acute rectal toxicities (Gr 0: 20; Gr 1: 10; Gr 2: 0; Gr 3-4: 0) were very modest. The mean IPSS scores at baseline, end of treatment and 3 months after treatment were 8.8, 14.7, and 9.9. With a median follow up of 23.7 months, the 2 year biochemical control was 96%. Late grade 2 rectal bleeding developed in 1 patient. Conclusions: Carefully planned stereotactic VMAT/HT based once-weekly SRT to a predominantly high-risk non-metastatic PrCa cohort was very well tolerated and found to be safe for clinical use. Preliminary biochemical control and late toxicity profiles are encouraging. Clinical trial information: CTRI/2016/02/006671. [Table: see text]

Analysis of Dose Calculation Accuracy in Cone Beam Computed Tomography with Various Amount of Scattered Photon Contamination

Cone-beam computed tomography (CBCT) images have inaccurate CT numbers because of scattered photons. Thus, quantitative analysis of scattered photons that affect an electron density (ED) curve and calculated doses may be effective information to achieve CBCT-based radiation treatment planning. We quantitatively evaluated the effect of scattered photons on the accuracy of dose calculations from a lung image. The Monte Carlo method was used to calculate CBCT projection data, and we made two calibration curves for conditions with or without scattered photons. Moreover, we applied cupping artifact correction and evaluated the effects on image uniformity and dose calculation accuracy. Dose deviations were compared with those of conventional CT in conventional and volumetric intensity modulated arc therapy (VMAT) planning by using γ analysis and dose volume histogram (DVH) analysis. We found that cupping artifacts contaminated the scattered photons, and the γ analysis showed that the dose distribution was most decreased for a scattered photon ratio of 40%. Cupping artifact correction significantly improved image uniformity; therefore, ED curves were near ideal, and the pass rate results were significantly higher than those associated with the scattered photon effect in 65.1% and 78.4% without correction, 99.5% and 97.7% with correction, in conventional and VMAT planning, respectively. In the DVH analysis, all organ dose indexes were reduced in the scattered photon images, but dose index error rates with cupping artifact correction were improved within approximately 10%. CBCT image quality was strongly affected by scattered photons, and the dose calculation accuracy based on the CBCT image was improved by removing cupping artifacts caused by the scattered photons.

Гипертермия как дополнительная опция в лечении больных плоскоклеточным раком анального канала

Purpose: to estimate the rate of locoregional recurrence and distant metastases, and the grade of chemoradiotherapy toxicity when in combination with local hyperthermia for treating squamous cell anal canal cancer T1-4N0,1-3M0-1. Materials and methods. 112 patients with squamous cell anal canal cancer were treated between 2011 and 2015 with chemotherapy, radiation therapy based on 3D CRT, intensity-modulated radiation therapy (IMRT) and volumetric intensity modulated arc therapy (VMAT), and local hypothermia. Staging was based on TNM (7th edition): I - 4 (3.6%) patients, II - 39 (34.8%) patients; IIIA - 33 (29.5%) patients, IIIB - 34 (30.3%) patients and IV - 2 (1.8%) patients. The median of mean follow-up was 32 months (range, 3-63 months). Local hyperthermia was performed in 81 (72.3%) patients. Results. 2-year local control was 73.2%. All recurrences, no matter which chemotherapy was performed, were in patients with advanced disease (IIIA/IIIB stages), from which 22.2% relapses were in group without local hyperthermia vs. 4.7% in group with radiomodification, p=0.038. Distant metastases were found in 9.4% patients with hyperthermia and in 11.1% patients without radiomodification, p=1. Usage of local hyperthermia is associated with increase II grade of dermatological toxicity (p=0.056). Conclusion. The combination of local hyperthermia and modern technologies of conformal radiation therapy has influenced the decrease of locoregional recurrences, but it is associated with lack of influence on distant metastases appearance regardless on chemotherapy regimen.

A circular matrix-merging algorithm with application in Volumetric Intensity-Modulated Arc Therapy

In this paper, we study an optimization problem, called the circular matrix-merging (CMM) problem: Given a cyclic sequence of n non-negative matrices that are associated with some locations on a circle and an operation that merges two consecutive matrices into one matrix at the expense of some merging error, merge the n matrices into the minimum number of matrices under the constraint of a threshold of the total merging error. This problem arises in Volumetric Intensity-Modulated Arc Therapy (VMAT) for radiation cancer treatment, where the circular structure represents a delivery arc path of 360° around the patient and the matrices represent the radiation fluence maps at selected delivery angles on that path. By computing the minimum k matrices, the CMM algorithm produces a most efficient delivery plan that meets clinical requirements. Based on dynamic programming and computing a set of k-link shortest paths, we present a polynomial time algorithm for the CMM problem, improving the quality and efficiency of VMAT delivery.

Volumetric intensity modulated arc therapy for stereotactic body radiosurgery in oligometastatic breast and gynecological cancers: feasibility and clinical results.

In the present study, the preliminary results of the first stereotactic body radiosurgery (SRS) experience with volumetric intensity modulated arc therapy (VMAT) in oligometastatic breast and recurrent gynecological tumors (OBRGT) are reported in terms of feasibility, toxicity and efficacy. Patients were treated in a head-first supine treatment position on a customized body frame immobilization shell. SRS-VMAT treatment plans were optimized using the ERGO++ treatment planning system. Response assessment was performed 8-12 weeks after treatment by morphologic imaging modalities, or if feasible, also by functional imaging. Thirty-six lesions in 24consecutive patients (median age, 63years; range, 40-81) were treated: 13.9% had primary or metastatic lung lesions, 30.5% had liver metastases, 36.1% had bone lesions, 16.7% had lymph node metastases and 2.8% had a primary vulvar melanoma. The median dose was 18Gy (BED2Gy, α/β: 10=50.4Gy), the minimal dose was 12Gy (BED2Gy, α/β: 10=26.4Gy) and the maximal dose was 28Gy (BED2Gy, α/β: 10=106.4Gy). Seven patients (29.2%) experienced acute toxicity, which however was grade2 in only 1case. Moreover, only 3patients (12.5%) developed late toxicity of which only 1 was grade2. Objective response rate was 77.7% including 16lesions achieving complete response (44.4%) and 12lesions achieving partial response (33.3%). The median duration of follow-up was 15.5months (range, 6-50). Recurrence/progression within the SRS-VMAT treated field was observed in 6patients (total lesions=7) with a 2-year inside SRS-VMAT field disease control expressed on a per lesion basis of 69%. Recurrence/progression of disease outside the SRS-VMAT field was documented in 15patients; the 2-year outside SRS-VMAT field metastasis‑free survival, expressed on a per patient basis, was 35%. Death due to disease was documented in 6patients and the 2-year overall survival was 58%. Although the maximum tolerated dose was not reached, SRS-VMAT resulted in positive early clinical results in terms of tumor response, local control rate and toxicity.