Dosimetric Parameters Research Articles

Patient, tumour, and dosimetric factors influencing survival in non-small cell lung cancer patients treated with stereotactic ablative body radiotherapy.

We aimed to analyse clinical outcomes of peripheral, early-stage non-small cell lung cancer (NSCLC) patients treated with stereotactic ablative body radiotherapy (SABR), and evaluate potential patient, tumour, and dosimetric variables influencing survival. Data were collected retrospectively from patients treated between September 2012 and December 2016 and followed up until January 2021. Patient demographics, tumour characteristics, SABR dosimetric parameters, and survival data were collected from electronic patient medical records. Descriptive statistics were performed, and SPSS software was used for survival analysis. Eighty-nine patients were included of whom 49.5% were male and 50.5% female. Median age was 74 years. 98.8% of patients had T1-2 tumours and 89.9% underwent 55 Gy in 5 fractions. Median overall survival time was 58.7 months. On uni- and multi-variate analysis, neither patient nor tumour variables showed association with overall survival. However, planning target volume (PTV) and minimum dose to PTV correlated with overall survival. There was a signal for association between mean lung dose and overall survival on multivariate analysis. Our long-term results show SABR is an effective treatment for peripheral, early-stage NSCLC with excellent overall survival, comparable to other series. Our study found only the PTV and minimum dose to PTV had an impact on overall survival, which demonstrates the importance of generating optimal SABR plans. Our work identified lung SABR dosimetric parameters that correlate with survival, which illustrates the importance of producing optimal lung SABR plans.

Dose advantage of abdominal deep inspiratory breath-hold (aDIBH) in postoperative adjuvant radiotherapy for left breast cancer

PurposeWe explored the dosimetric efficacy of the abdominal deep inspiration breath hold (aDIBH) technique using an audio-guided device in patients with left breast cancer undergoing postoperative adjuvant radiotherapy compared to free breathing (FB).MethodsA total of 35 patients with early stage left breast cancer underwent two computed tomography simulation scans each with aDIBH and FB after breast-conserving surgery. Treatment planning was optimized using the Pinnacle3 9.10 planning system. The heart, left anterior descending coronary artery (LADCA), and left lung was defined as organs at risk (OARs). The dosimetric differences in the planning target volume (PTV) and OARs were compared between aDIBH and FB.ResultsCompared with FB, the heart moved farther caudally and away from the chest wall, and the volume of heart became smaller under aDIBH due to expansion of the lungs. The D mean of the heart, LADCA and left lung of aDIBH were respectively reduced by 332.79 ± 264.61 cGy (P < 0.001), 1290.37 ± 612.09 cGy (P < 0.047) and 69.94 ± 117.73 cGy (P < 0.001). The V20 and V30 of the OARs were also significantly reduced with statistical differences (P < 0.05). In addition, there was no significant difference in the dosimetric parameters of the PTV between the two groups (P > 0.05).ConclusionsImplementation of the aDIBH technique for postoperative radiotherapy after breast-conserving surgery of the left breast cancer could reduce irradiation of the heart dose, LADCA dose and left lung dose, without compromising target coverage.

Dosimetric Comparison between the HyperArc and Conventional VMAT in Cervical Spine Stereotactic Radiosurgery.

Background: This research aims to evaluate the usability of the HyperArc (HA) technique in stereotactic radiosurgery for cervical spine metastasis by comparing the dosimetry of the target and organs at risk, specifically the spinal cord, between HA and VMAT and conventional volumetric modulated arc therapy (VMAT). Methods: A RANDO® phantom and QFix EncompassTM and support system were used to simulate three target types (A, B, and C) based on RTOG0631 guidelines. Treatment plans included one VMAT and two HyperArc techniques with different SRS NTO values (100 and 250). Dosimetric parameters such as conformity index (CI), homogeneity index (HI), R50, and spinal cord sparing were analyzed. Gamma analysis was performed using portal dosimetry to validate the dose delivery accuracy. Results: HyperArc plans demonstrated higher conformity, sharper dose fall-off, and improved quality assurance (QA) results compared to VMAT plans. HA with SRS NTO 250 showed even better results in terms of conformity, dose fall-off, and spinal cord dose reduction (V10 and Dmax) compared to HA with SRS NTO 100. Although the mean gamma passing rates were slightly lower, all plans achieved rates above 95%. Conclusion: The findings suggest that HA provides superior dosimetric benefits over VMAT and could be effectively utilized for cervical spine radiation therapy.

Helical to wide volume acquisition in lumbar spine CT: Structures scoring based analysis

This study aims to compare the effectiveness of standard helical CT (HMCT) and volume CT (VMCT) protocols for lumbar spine imaging in terms of radiation dose and image quality. Two groups of 56 patients each (32 males, 24 females) who underwent lumbar spine CT were evaluated. The first group was imaged using HMCT and the second with VMCT. Dosimetric parameters including CTDIvol, DLP, and SSDE for both protocols were assesed and compared to evaluate radiation exposure. Image quality was assessed through quantitative analysis of Hounsfield Units (HU) and image noise, and qualitative analysis based on anatomical structure scoring by four reviewers. The VMCT protocol significantly reduced the mean CTDIvol (13 ± 3 mGy vs. 26 ± 6 mGy), DLP (270 ± 29 mGy cm vs. 609 ± 71 mGy cm), and effective dose (5 ± 0 mSv vs. 11 ± 1 mSv) compared to HMCT. SSDE was also lower for VMCT (15.6 ± 4.8 mGy) versus HMCT (31.8 ± 9.1 mGy). Despite this reduction in radiation dose, VMCT showed increased image noise across all anatomical regions, though differences in HU values were region-specific. Qualitative scoring revealed that VMCT images were similar in clarity and sharpness to HMCT images, with only marginally lower scores for most structures. VMCT significantly reduces radiation exposure compared to HMCT with observed difference in noise and CT number. The VMCT protocol can represent a promising tool in terms of radiation protection of patients while image quality needs further evaluation to take into consideration other parameters.

Personalized selection of unequal sub-arc collimator angles in VMAT for multiple brain metastases

PurposeInvestigating the effects of unequal sub-arc personalized collimator angle selection on the quality of Volumetric Modulated Arc Therapy (VMAT) plans for treating multiple brain metastases. MethodsThis study included 21 patients, each with 2–4 target volumes of multiple brain metastases. Two stereotactic radiotherapy (SRT) approaches were utilized: sub-arc collimator VMAT (SAC-VMAT) and fixed collimator VMAT (FC-VMAT). In the SAC-VMAT group, multi-leaf collimators (MLC) shaped the target area, dividing the full arc into four unequal sub-arcs under the beam's eye view (BEV). Each sub-arc had an appropriate collimator angle selected to mitigate ‘island blocking problems'. Conversely, the FC-VMAT group used a fixed collimator angle of 15° or 345°. A comparative analysis of the dosimetric parameters of the target volumes and normal tissues, along with the monitor units (MU), was conducted between the two groups. ResultsThe mean dose and dose-volume to normal brain tissue (2–26 Gy, with a step of 2 Gy) were significantly lower in the SAC-VMAT group (P < 0.01). There was no statistical difference between the two groups in dose to the target volumes, conformity index (CI), homogeneity index (HI), and other normal tissues (P > 0.05). Compared with the FA-VMAT group, the SAC-VMAT group significantly reduced the gradient index (GI) (4.5 ± 0.59 vs 5.2 ± 0.75, P < 0.001) and MU (1774.33 ± 181.77 vs 2001.0 ± 344.86, P < 0.001). Notably, with an increase in the number of PTV, the SAC-VMAT group demonstrated more significant improvements in the dose-volume of normal brain tissue, GI, and MU. ConclusionsIn this study, personalized selection of the unequal sub-arc collimator angle ensured the prescribed dose to the PTV, CI, and HI, while significantly reducing the GI, MU, and the dose to normal brain tissue in the VMAT plan for multi-target brain metastases in the cohort of cases with 2–4 target volumes. Particularly as the number of targets increase, the advantages of this method become more pronounced.

Exploring the impact of field shape on predicted dose distribution in breast cancer patients using deep learning in radiation therapy

BackgroundGeometrical information such as field shape is essential for dose calculation in radiation therapy. However, new methods of dose prediction based on deep learning only use CT images and contouring of patients. The aim of this study is to develop a deep learning method for three-dimensional dose prediction for breast cancer radiotherapy using field shape as well as CT and contouring images of patients. MethodsA total of 150 breast cancer patients' data treated with 3D conformal radiation therapy (CRT) technique were used to train and test 3D-U-Res-F-Net model. The model inputs were CT images, patients' contouring and field shape. The network output was the corresponding the patients’ dose distribution. Then, the dosimetric parameters extracted from the dose volume histograms related to the planned and predicted dose distributions were compared and were statistically analysed with the paired-samples t-test. These parameters include Dmean and Dmax for planning target volume and organs at risk, D95%, D50%, V47.5Gy for PTV, V30Gy and V25Gy for heart and V20Gy for left lung. The gamma index with 3%/3 mm criteria was calculated for PTV and OARs. ResultsThe average absolute difference of the Dmean relative to the prescribed dose for the PTV, heart, left lung, right lung and spinal cord were 1.37 ± 0.4%, 2.02 ± 2%, 2.12 ± 1%, 0.37 ± 0.3% and 0.41 ± 0.3%, respectively. The average absolute difference of the Dmax relative to the prescribed dose for the PTV and OARs varied from 0.23 ± 0.2% to 2.04 ± 2%. The 3D gamma pass rate with 3mm/3% criteria for planning target volume, heart, left lung, right lung, spinal cord and body were 89 ± 3%, 91 ± 5%, 93 ± 5%, 99 ± 3%, 99 ± 1% and 96 ± 2% respectively. ConclusionsThe results of the proposed model demonstrate that there is no significant difference between the predicted and planned dose distributions. The deep learning model can directly predict the 3D dose distribution faster than treatment planning systems. Further studies with more patients and on other cancer sites are essential to fully validate the proposed method.

Evaluation of Inverse Planned and Forward Planned Intensity Modulated Radiotherapy Techniques in Breast Cancer

Introduction: The objective of this study is to compare the dosimetric parameters of radiation to the whole breast between the two intensity-modulated radiotherapy (IP IMRT) techniques, i.e. Inverse planned IMRT (IP IMRT) and Forward Planned IMRT (FP IMRT) with regard to target coverage (PTV) and irradiation of organs at risk (OAR). Material and Methods: Plain and Contrast enhanced computed tomography (CECT) datasets were created for 41 patients treated with whole breast radiation therapy. CT simulation and treatment is performed using deep inspiratory breath hold technique (DIBH). Radiotherapy treatment Planning is done using Eclipse Treatment Planning System (version 13.7) with a prescription dose of 40 Gy in 15#. The developed treatment plans were subjected to objective comparison of PTV and OARs using dose volume histograms (DVH). Results: IP IMRT plans provided better coverage (99.5% vs 97.6%), comparable though higher maximum dose (Dmax 45.0 VS 44.1 Gy), higher hot spot (PTV105% 49.2 vs 33), lower volumes receiving 20, 25, 30 Gy (V20, V25, V30) for heart, more homogeneous (homogeneity index 0.10 vs. 0.14) and conformal dose distribution (conformity Index 1.0 vs 0.98) compared to FP IMRT. Regarding OAR dosimetry it is observed that FP IMRT showed reduced mean dose to Coronary artery (LADCA), Contralateral Lung (CL), Contralateral breast (CB) along with reduction in low dose region (V5) to all OARs under study. It was also observed that Monitor units used and planning time were lower for FP IMRT. Conclusion: On weighing different dosimetric factors, both the techniques have displayed their own advantages and disadvantages. Choosing a planning technique needs to be customized taking into consideration various factors such as breast topography, size and volumes of breast, availability of expertise planning skills and resources.

Brachial plexopathy following stereotactic body radiation therapy in apical lung malignancies: A dosimetric pooled analysis of individual patient data

Background and objectivesThe aim of this study is to establish dosimetric constraints for the brachial plexus at risk of developing grade ≥ 2 brachial plexopathy in the context of stereotactic body radiation therapy (SBRT). Patients and MethodsIndividual patient data from 349 patients with 356 apical lung malignancies who underwent SBRT were extracted from 5 articles. The anatomical brachial plexus was delineated following the guidelines provided in the atlases developed by Hall, et al. and Kong, et al.. Patient characteristics, pertinent SBRT dosimetric parameters, and brachial plexopathy grades (according to CTCAE 4.0 or 5.0) were obtained. Normal tissue complication probability (NTCP) models were used to estimate the risk of developing grade ≥ 2 brachial plexopathy through maximum likelihood parameter fitting. ResultsThe prescription dose/fractionation schedules for SBRT ranged from 27 to 60 Gy in 1 to 8 fractions. During a follow-up period spanning from 6 to 113 months, 22 patients (6.3 %) developed grade ≥2 brachial plexopathy (4.3 % grade 2, 2.0 % grade 3); the median time to symptoms onset after SBRT was 8 months (ranged, 3–54 months). NTCP models estimated a 10 % risk of grade ≥2 brachial plexopathy with an anatomic brachial plexus maximum dose (Dmax) of 20.7 Gy, 34.2 Gy, and 42.7 Gy in one, three, and five fractions, respectively. Similarly, the NTCP model estimates the risks of grade ≥2 brachial plexopathy as 10 % for BED Dmax at 192.3 Gy and EQD2 Dmax at 115.4 Gy with an α/β ratio of 3, respectively. Symptom persisted after treatment in nearly half of patients diagnosed with grade ≥2 brachial plexopathy (11/22, 50 %). ConclusionsThis study establishes dosimetric constraints ranging from 20.7 to 42.7 Gy across 1–5 fractions, aimed at mitigating the risk of developing grade ≥2 brachial plexopathy following SBRT. These findings provide valuable guidance for future ablative SBRT in apical lung malignancies.

Stereotactic body radiotherapy using CyberKnife versus interstitial brachytherapy in accelerated partial breast irradiation on left-sided breast: A comparison of dosimetric characteristics and preliminary clinical results

IntroductionWe compared the dosimetric characteristics of the target and organs at risk (OARs) as well as the preliminary clinical outcomes between two accelerated partial breast irradiation (APBI) techniques. MethodsForty-four patients diagnosed with left-sided early breast cancer who underwent APBI using either interstitial brachytherapy (IB) or stereotactic body radiation therapy (SBRT) with CyberKnife (CK) were retrospectively reviewed. The dosimetric parameters of the target and OARs were compared. Preliminary clinical outcomes, including tumor control and acute toxicity, were analyzed. ResultsTreatment plans with CK demonstrated a better cardiac dose-sparing effect. Radiation doses to the heart at V150cGy for the CK and IB groups were 24.4 % and 60.4 %, respectively (p < 0.001), while the mean heart doses for the CK and IB groups were 107.4 cGy and 204 cGy, respectively (p < 0.001). The heart D1c.c. and the ipsilateral lung received a lower dose in the IB group, without any significant differences. The median follow-up time in the CK and IB groups was 28.6 and 61.3 months, respectively. No patients died from either breast cancer or cardiac events during follow-up. A locoregional recurrence event at the neck occurred in one patient within the IB group. ConclusionsAPBI planned by CK was shown to have a better dose-sparing effect on the heart, as well as better conformity and homogeneity to the target. CK is a non-invasive treatment which showed minimal acute toxicity and promising tumor control.

Effect of body contour changes on the setup and dosimetric accuracy of radiotherapy after cervical cancer surgery.

The body contour of patients with cervical cancer is prone to change between radiotherapy sessions. This study aimed to investigate the effect of body contour changes on the setup and dosimetric accuracy of radiotherapy. 15 patients with cervical cancer after surgery were randomly selected for retrospective analysis. The body contours on the once-per-week cone-beam computed tomography (CBCT) were registered to the planning CT (pCT) for subsequent evaluation. A body contour conformity index (CIbody) was defined to quantify the variation of body changes. The body volume measured by CBCT was collected, and its relative difference in reference with the first CBCT was calculated and denoted by ΔVn. The relative setup errors, denoted by ΔSELR, ΔSEAP, ΔSESI, and ΔSEvec for left-right, anterior-posterior, superior-inferior, and vectorial shifts, respectively, were defined as the difference in measured setup errors between the reference and following CBCTs. The planned dose was calculated on the basis of virtual CT generated from CBCT and pCT by altering the CT body contour to fit the body on CBCT without deformable registration. The correlations between body contour changes and relative setup errors as well as dosimetric parameters were evaluated using Spearman's correlation coefficient rs . CIbody was found to be negatively correlated with the superior-inferior and vectorial relative setup errors ΔSESI (rs = -0.448, p = 0.001) and ΔSEvec (rs = -0.387, p = 0.002), and no significant correlation was found between relative setup errors and ΔVn. Moreover, ΔVn was negatively correlated with ΔD2 (rs = -0.829, p < 0.001), ΔD98 (rs = -0.797, p < 0.001), and ΔTVPIV (rs = -0.819, p < 0.001). ΔD2, ΔD98, and ΔTVPIV were negatively correlated with ΔVn (p < 0.005). No correlation was found for other examined dosimetric parameters. The body contour change of patients could be associated with the setup variability. The effect of body contour changes on dose distribution is minimal. The extent of body change could be used as a metric for radiation therapists to estimate the setup errors.

Dose prediction for cervical cancer in radiotherapy based on the beam channel generative adversarial network

BackgroundExisting deep learning methods, such as generative adversarial network (GAN) technology, face challenges when dealing with mixed datasets, which involve a combination of Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT). This issue significantly complicates the application of dose prediction in the field of radiotherapy. In this study, we propose a novel approach called beam channel GAN (Bc-GAN) to address the task of radiation dose prediction for mixed datasets. Bc-GAN introduces a dose prediction calculation method that requires less precision. By defining an approximate range for dose prediction, Bc-GAN limits the physical range of GAN prediction, resulting in more reasonable dose distribution predictions. MethodsWe adopt a beam angle weighting method to determine the beam angle in the dose calculation. The dose of the beam with the highest weight is calculated using medical images and is then inputted into the artificial intelligence dose prediction model as the input channel. Additionally, we collect data from a total of 346 patients with Cervical Cancer (CC) for dataset. After cleaning the data, we exclude 51 cases with incomplete organ delineation, leaving us with 295 cases (IMRT: VMAT = 137:158) randomly divided into three sets: the training set, the validation set, and the test set, with proportions of 205:60:30, respectively. The assessment of model predictions was conducted via an analysis of dose distributions on the tomographic plane, dose volume histogram (DVH), and dosimetric parameters within the target zones and organs at risk (OAR). ResultsAfter DVH analysis, minimal discrepancy was found between predicted and actual dose distributions in PTV and OAR. The predicted distribution aligned with clinical standards. Dosimetric parameters for PTV were generally lower in the predicted model, except for homogeneity index (HI) (0.238 ± 0.024, P = 0.017) and Dmax (53.599 ± 0.710 Gy, P = 1.8e-05). The prediction model varied in estimating doses for six organs. Specifically, small intestine showed higher V20 (67.92 ± 51.64 %, P = 0.019) and V30 (57.171 ± 1.213 %, P = 0.024) than manual planning. A similar trend was seen in colon's V30 (37.13 ± 61.14 %, P = 0.016). However, predicted bladder V30 (87.51 ± 41.44 %, P = 2.03e-16) was lower, indicating significant dosimetric differences. ConclusionOverall, this study presents an innovative prediction method for CC in radiotherapy using the Bc-GAN model, addressing the challenges posed by different radiotherapy techniques. The proposed approach allows IMRT and VMAT in radiotherapy to be used as training sets, enabling the potential for large-scale engineering and commercialization applications of artificial intelligence (AI). The Bc-GAN-based prediction method for CC in radiotherapy not only reduces the amount of data needed for the training set but also expedites the model generation process. This approach can be applied to guide the development of clinical radiation therapy plans. Furthermore, future studies should consider extending the dose prediction method to encompass other types of tumors.

Reirradiation of Utracentrally Located Thoracic Tumors Using a 10-Fraction Hypofractionated Stereotactic Body Radiation Therapy Course: A Detailed Dosimetric Analysis

PurposeThere is very little information detailing outcomes and toxicity following re-irradiation for ultracentrally located thoracic tumors, and detailed dosimetric data is non-existent. This data is critical for the safe management of these extremely difficult cases. Materials and MethodsThe records of fifteen individuals undergoing 10-fraction hypofractionated stereotactic body radiotherapy (hfSBRT) for the management of ultracentrally located thoracic tumors between 2009 and 2020 at a single institution were retrospectively reviewed. Treatment outcomes and toxicity were analyzed. A detailed dosimetric analysis of treatment plans and centrally located organs at risk (OARs), from the initial, re-irradiation, and cumulative radiotherapy courses was presented. ResultsAt a median follow up of 10 months, one- and three-year overall survival (OS), progression free survival (PFS) and local control (LC) were 52% and 28%, 33% and 28%, and 76% and 61%, respectively. Treatment related adverse events were low with 5 individuals (33%) developing ≥ grade 2 pneumonitis (Grade 2 = 4, Grade 3 = 1). Dosimetric parameters were not associated with the development of clinically relevant pneumonitis. No adverse events involving central OARs (esophagus, great vessels, primary bronchial tree) were identified. Median cumulative mean lung dose (MLD) was 24 Gy (EQD2) (range: 10-33 Gy), with a V20 of 33% (range: 11-51%). Median esophageal, primary bronchial tree, and great vessel maximum doses (Dmax) were 93.2 Gy (EQD2) (range: 50-148 Gy), 163 Gy (range: 77-204 Gy), and 191 Gy (range: 129-262 Gy), respectively. ConclusionsThe current investigation is the first to provide detailed cumulative dosimetric data from a cohort of patients comprised entirely of ultracentrally located thoracic tumors. Despite unfavorable anatomic tumor location given an intimate association to critical OARs, delivering an ablative dose with a 10-fraction hfSBRT course can serve as a feasible option for these challenging cases.

Predictive Value of Simulated CT Radiomics Combined with Ipsilateral Lung Dosimetry Parameters for Radiation Pneumonitis in Patients with Esophageal Cancer: A Machine Learning-Based Retrospective Study.

To explore how non-surgical esophageal cancer patients can identify high-risk factors for radiation-induced pneumonitis after receiving radiotherapy. We retrospectively included 228 esophageal cancer patients who were unable to undergo surgical treatment but received radiotherapy for the first time. By retrospective analysis and identifying potential risk factors for symptomatic radiation-induced pneumonitis (ie ≥grade 2), as well as delineating the affected lung as an area of interest on localized CT and extracting radiomics features, along with extracting dosimetric parameters from the affected lung area. After feature screening, patients were randomly divided into training and testing sets in a 7-to-3 ratio, and a prediction model was established using machine learning algorithms. Finally, the receiver operating characteristic (ROC) curve and decision curve analysis (DCA) were used to validate the predictive performance of the model. A total of 54 cases of symptomatic radiation pneumonitis occurred in this study, with a total incidence rate of 23.68%. The results of multivariate analysis showed that the occurrence of symptomatic radiation pneumonitis was significantly correlated with the mean lung dose (MLD), esophageal PTVD90, esophageal PTVV50, V5, V10, V15, and V20 in patients. The machine learning prediction model constructed based on candidate prediction variables has a prediction performance interval between 0.751 (95% CI: 0.700-0.802) and 0.891 (95% CI: 0.840-0.942) in the training and validation sets, respectively. Among them, the RFM algorithm has the best prediction performance for radiation-induced pneumonitis, with 0.891 (95% CI: 0.840-0.942) and 0.887 (95% CI: 0.836-0.938) in the training and validation sets, respectively. The combination of localization CT radiomics features and diseased lung dosimetry parameters has good predictive value for radiation-induced pneumonitis in esophageal cancer patients after radiotherapy. Especially, the radiation-induced pneumonitis prediction model constructed using RF algorithm can be more effectively used to guide clinical decision-making in esophageal cancer patients.

3D-printed individual template brachytherapy for the treatment of intractable central pelvic recurrent cervical cancer: A single institution experience

OBJECTIVEThe prognosis of recurrent cervical cancer tends to be poor and there are limited effective treatments currently available for these patients. This study was developed to find a safe and effective treatment for patients with central pelvic recurrent cervical cancer. MATERIALS AND METHODSThis retrospective study analyzed patients with central pelvic recurrent cervical cancer who received 3D-printed individual template (3D-PIT) brachytherapy between February 2019 and June 2023. Analyses of dosimetric parameters, toxicity-related complications, and survival were conducted based on the data of these patients. RESULTSTwenty-one patients with central pelvic recurrent cervical cancer patients were enrolled. All of them received 3D-printed individual template (3D-PIT) brachytherapy. The mean respective adjusted cumulative HRCTV-D90 and HRCTV-D98 values for these patients were 86.9 Gy and 75.4 Gy. And the local control (LC) rate of these patients was 57.1%. In these 21 patients, only 2 (9.5%) of them experienced grade 3–4 rectal adverse reactions, while 7 (33.3%) patients experienced grade 3–4 bladder adverse reactions. 5(23.8%) patients had fistula, while 3 of these 5 patients had undergone prior anti-VEGF targeted drug treatment which is a risk factor of fistula. The respective 2-year rates of overall and progression-free survival (OS and PFS) for these patients were 72.9% and 57.4%, with a 26-month median PFS. CONCLUSIONSThese single-institution data highlight the potential viability of 3D-PIT brachytherapy as an approach to managing intractable central pelvic recurrent cervical cancer following first-line treatment.

Image-guided brachytherapy for pediatric bladder and/or prostate rhabdomyosarcoma: toward an increased personalization of treatment.: Brachytherapy in uro-pediatric rhabdomyosarcoma

IntroductionRhabdomyosarcoma (RMS) is the most common soft tissue cancer in children. Around 15% of RMS involve the bladder and/or prostate (BP). Overall survival is around 85%. After chemotherapy, patients receive local treatment based on surgery and/or radiotherapy. In recent decades, image guidance and pulsed dose-rate (PDR) brachytherapy have made it possible to personalize treatment, reduce radiation-related toxicity, while maintaining a good tumor control. We report one of the largest series of image-guided brachytherapy for pediatric RMS BP. Material and methodsThe clinical and dosimetric parameters of children treated with brachytherapy for BP RMS between July 2014 and September 2020 were retrospectively reviewed. Patients were treated with a multimodal conservative approach, combining partial conservative surgery (preservation of the bladder neck and urethra), followed by an interstitial brachytherapy procedure. Iridium-192 PDR treatment was administered on the basis of CT and MRI planning. Toxicities were reported according to version 4.0 of the Common Terminology Criteria for Adverse Events. ResultsA total of 75 patients were identified, with a median age of 29 months (range 2–84) at diagnosis. The median brachytherapy dose was 60.06 Gy (143 pulses, 0.42 Gy/pulse). With a median follow-up of 44.1 months (range 0.7–90), the 5-year OS and PFS rates were 97.3% and 92% respectively. Median D50% for the bladder and D1cc for the rectum were 38.6 Gy and 49 Gy respectively. The 5-year probability of survival without severe late urinary toxicity (grade 3 or higher) was estimated at 78.8% (CI95%: 68.1–91.1). A total of 9.3% of children experienced grade 2 or 3 late rectal toxicity. ConclusionsImage-guided PDR brachytherapy offers a personalized treatment for pediatric BP RMS, with a favorable therapeutic index. No prognostic factors for urinary toxicity have been identified. Multicenter studies with larger numbers of patients are needed to clarify these data.

Adjuvant modern radiotherapy in resected pN2 NSCLC patients: results from a multicentre retrospective analysis on acute and late toxicity on behalf of AIRO thoracic oncology study group: the RAC-TAC study.

Recently, the PORT-C and LUNG-ART trials, which evaluated the role of postoperative radiation therapy (PORT), have significantly altered the treatment landscape for NSCLC pN2 patients who previously underwent surgery. In response, the Italian Association of Radiotherapy and Oncology Thoracic Oncology study group has initiated an observational multicenter trial to assess both acute and late toxicities of PORT in pN2 NSCLC patients treated with modern techniques. Data on NSCLC patients submitted to PORT after radical surgery treated between 2015 and 2020 in six Italian Centers were collected. Heart, lung, and esophageal acute and late toxicities have been retrospectively analyzed and related to radiation therapy dosimetric parameters. Furthermore, loco-regional control, distant metastasis and overall survival have been analyzed. A total of 212 patients with a median age of 68years from six different centers were included in this analysis (142 males and 70 females). Prior to undergoing PORT, 96 patients (45.8%) had a history of heart disease, 110 patients (51.9%) had hypertension, and 51 patients (24%) had COPD. Acute toxicity was observed in 147 patients (69.3%), with lung toxicity occurring in 93 patients (G1 in 70 patients, G2 in 17 patients, and G3 in 4 patients), esophageal toxicity in 114 patients (G1 in 89 patients, G2 in 23 patients, and G3 in 1 patient), and cardiac toxicity in 4 patients (G1 in 2 patients and G3 in 2 patients). Late side effects were found in 60 patients (28.3%), predominantly involving the lungs (51 patients: 32 G1, 11 G2, and 1 G3) and the esophagus (11 patients: 8 G1 and 3 G2), with no reported late cardiac side effects. Various clinical and dosimetric parameters were found to correlate with both acute and chronic toxicities. Over a median follow-up period of 54months, 48 patients (22.6%) showed locoregional disease relapse, 106 patients (50%) developed distant metastases, and 66 patients (31.1%) died. RAC-TAC retrospective multicentric study showed the low toxicity of PORT when advanced technology is used. At the same time, it's noteworthy to underline that 50% of the patients develop distant recurrences in the follow up.

Beam profile characteristics of a Varian linear accelerator across different photon energy levels

Radiotherapy employs variety of energy radiation to destroy cancer cells. A linear accelerator(also called LINAC) is the machine used to delivered external beam radiation therapy.In order to confirm the treatment planning systems that deliver the best radiation to the tumors while sparing the surrounding normal tissues, extensive measurements of dosimetric parameters are part of the commissioning procedure of a LINAC for clinical usage. This work aimed to compare and assess photon beam profiles with respect to penumbra width, symmetry, and beam flatness. Beam profile measurements were performed for this study atTMSS Cancer Center, Bogura, Bangladesh, using a linear accelerator (Varian VitalBeam SN: 5199) with 6MV,10MV and 15MV photon energies for a set of field sizes (4 × 4, 10 × 10 and 20 × 20 cm2) and various reference depths keeping the same environmental conditions. A 3D water phantom, CC13 ionization chamber (SN:18635)as a reference chamber, CC04 ionization field chamber (SN:18616) as a and IBA myQA Accept software version 1.6 were used to measure the profiles of photon energies 6 MV, 10 MV 15 MV respectively. Utilizing the Eclipse (Version: 16.1) external treatment planning system, the profile calculation was carried out. According to the manufacturer's and IEC specifications, the photon beam profile data from the current investigation are compatible, and all of the tolerances fall within the ranges of clinically acceptable tolerance.

A novel x-Ray and γ-Ray combination strategy for radiotherapy after breast-conserving surgery in patients with right breast cancer.

Radiotherapy is a primary therapeutic approach for breast cancer following breast-conserving surgery. The TaiChiB dual-modality radiotherapy system combining X-ray and focused γ-ray, offers a new approach to reduce the radiation dose of organs at risk (OARs) and has the potential to mitigate the adverse effects of radiotherapy. Currently, there are few studies on the dosimetric characteristics of the TaiChiB dual-modality system for actual treatment plans for specific diseases. The purpose of this work is to study the dosimetric advantages of dual-modal systems for right breast patients after breast-conserving surgery. Treatment plans for 20 patients with right breast cancer were generated for a linear accelerator (LINAC) based system and the TaiChiB dual-modality system, respectively. Volumetric modulated arc therapy plans with simultaneous integrated boost (VMAT-SIB) were made for the LINAC. Focused γ-ray was used to deliver the boost dose with the dual-modality system. The dosimetric parameters of the target and OARs were evaluated and compared between the treatment plans generated for the two systems. The TaiChiB dual-modality plans exhibit a higher conformal index (CI) and lower gradient index (GI) for the PGTV and PTV compared with the LINAC-based VMAT-SIB plans. Compared to VMAT-SIB plans, the PTV Dmax, PTV Dmean, PTV V110, PGTV Dmax, and PGTV Dmean of the TaiChiB dual-modality plans are significantly lower. Meanwhile, the dose to OARs, such as the Dmean of the heart, the V5 of liver, the Dmean of ipsilateral lung, the V30 of ipsilateral lung, the V20 of ipsilateral lung, the V5 of ipsilateral lung, the Dmean of contralateral lung, Dmax of contralateral breast and the Dmean of contralateral breast are significantly reduced. Our study demonstrates the dosimetric advantages of the novel TaiChiB dual-modality radiotherapy system for the treatment of right-sided breast cancer. Overall, for the TaiChiB dual-modality radiotherapy system, the radiation dose outside the target region decreases rapidly, thereby minimizing radiation exposure to neighboring organs and ensuring the conformity of the target area. Our research confirms the potential of the TaiChiB dual-modality system for future radiotherapy.

The addition of pembrolizumab to neoadjuvant chemoradiotherapy did not increase the risk of developing postoperative anastomotic leakage for ESCC: an analysis from a prospective cohort

BackgroundTo compare the difference of postoperative anastomotic leakage (AL) rate between neoadjuvant chemoradiotherapy (NCRT) with pembrolizumab and NCRT group, and investigate the risk factors of developing AL for locally advanced esophageal squamous cell cancer (ESCC).Materials and methodsThe GF was contoured on the pretreatment planning computed tomography and dosimetric parameters were retrospectively calculated. Univariate and multivariate logistic regression analysis was performed to determine the independent risk predictors for the entire cohort. A nomogram risk prediction model for postoperative AL was established.ResultsA total of 160 ESCC patients were included for analysis. Of them, 112 were treated with NCRT with pembrolizumab and 44 patients with NCRT. Seventeen (10.6%) patients experienced postoperative AL with a rate of 10.7% (12/112) in NCRT with pembrolizumab and 11.4% (5/44) in NCRT group. For the entire cohort, mean, D50, Dmax, V5, V10 and V20 GF dose were statistically higher in those with AL (all p < 0.05). Multivariate logistic regression analysis indicated that tumor length (p = 0.012), volume of GF (p = 0.003) and mean dose of GF (p = 0.007) were independently predictors for postoperative AL. Using receiver operating characteristics analysis, the mean dose limit on the GF was defined as 14 Gy.ConclusionBased on our prospective database, no significant difference of developing AL were observed between NCRT with pembrolizumab and NCRT group. We established an individualized nomograms based on mean GF dose combined with clinical indicators to predict AL in the early postoperative period.

Cumulative rib fracture risk after stereotactic body radiotherapy in patients with localized non-small cell lung cancer

IntroductionRib fracture is a known complication after stereotactic body radiotherapy (SBRT). Patient-related parameters are essential to provide patient-tailored risk estimation, however, their impact on rib fracture is less documented compared to dosimetric parameters. This study aimed to predict the risk of rib fractures in patients with localized non-small cell lung cancer (NSCLC) post-SBRT based on both patient-related and dosimetric parameters with death as a competing risk. Materials and methodsIn total, 602 patients with localized NSCLC treated with SBRT between 2010–2020 at Odense University Hospital, Denmark were included. All patients received SBRT with 45–66 Gray (Gy)/3 fractions. Rib fractures were identified in CT-scans using a word embedding model. The cumulative incidence function was based on cause-specific Cox hazard models with variable selection based on cross-validation model likelihood performed using 50 bootstraps. ResultsIn total, 19 % of patients experienced a rib fracture. The cumulative risk of rib fracture increased rapidly from 6-54 months post-SBRT. Female gender, bone density, near max dose to the rib, V30 and V40 to the rib, gross tumor volume, and mean lung dose were significantly associated with rib fracture risk in univariable analysis. The final multi-variable model consisted of V20 and V30 to the rib and mean lung dose. ConclusionFemale gender and low bone density in male patients are significant predictors of rib fracture risk. The final model predicting cumulative rib fracture risk of 19 % in patients with localized NSCLC treated with SBRT contained no patient-related parameters, suggesting that dosimetric parameters are the primary drivers.