Deep Inspiration Breath-hold Radiotherapy Research Articles

424 - Feasibility of voluntary deep inspiration breath-hold radiotherapy technique (vDIBH-RT) implementation without DIBH-assisting device

424 - Feasibility of voluntary deep inspiration breath-hold radiotherapy technique (vDIBH-RT) implementation without DIBH-assisting device

Is intensive training with atime interval between instruction and planning CT necessary for deep inspiration breath-hold radiotherapy in breast cancer?

Breathing instruction and exercises and atime gap between training and planning CT scans (pCT) is recommended as part of deep inspiration breath-hold (DIBH) assisted radiotherapy (RT). However, this is associated with additional time expenditure. In two of the authors' treatment centers (TC), patient training took place before the planning CT of DIBH-assisted therapy. In TC1, afurther appointment was made with aminimum interval of 2days to perform the planning CT. At TC2, the planning CT was performed immediately after the first patient instruction. Aretrospective evaluation of the clinical parameters of the therapy was carried out to investigate the relevance of the time gap between DIBH exercises and pCT. Atotal of 72patients were included, 35 of whom were treated in TC1 and37 in TC2. In TC1, an average interval of ~4 days was observed between patient training and planning CT, while in TC2, training and CT were performed immediately after each other. No significant differences in radiation dose exposure of the lung on the treated side, the whole lung, or the heart were found between the two centers. Furthermore, there was no significant difference in the application of the daily RT fraction. The requirement for daily positioning checks was also the same at both treatment centers. This study does not show any advantages for atime gap between instruction/training and pCT. Skipping the time break does not deteriorate any clinically relevant endpoints.

1370: Systematic intrafraction drift motion of lymph nodes during lung cancer DIBH radiotherapy sessions

1370: Systematic intrafraction drift motion of lymph nodes during lung cancer DIBH radiotherapy sessions

Identification of variables and development of a prediction model for DIBH eligibility in left-sided breast cancer radiotherapy: a prospective cohort study with temporal validation

ObjectiveTo identify variables associated with a patients’ ability to reproducibly hold their breath for deep-inspiration breath-hold (DIBH) radiotherapy (RT) and to develop a predictive model for DIBH eligibility.MethodsThis prospective, single-institution, IRB-approved observational study included women with left-sided breast cancer treated between January 2023 and March 2024. Patients underwent multiple breath-hold sessions over 2–3 consecutive days. DIBH waveform metrics and clinical factors were recorded and analysed. Logistic mixed modelling was used to predict DIBH eligibility, and a temporal validation cohort was used to assess model performance.ResultsIn total, 253 patients were included, with 206 in the model development cohort and 47 in the temporal validation cohort. The final logistic mixed model identified increasing average breath-hold duration (OR, 95% CI: 0.308, 0.104–0.910. p = 0.033) and lower amplitude (OR, 95% CI: 0.737, 0.641–0.848. p < 0.001) as significant predictors of DIBH eligibility. Increasing age was associated with higher odds of being ineligible for DIBH (OR, 95% CI: 1.040, 1.001–1.081. p = 0.044). The model demonstrated good discriminative performance in the validation cohort with an AUC of 80.9% (95% CI: 73.0-88.8).ConclusionThe identification of variables associated with DIBH eligibility and development of a predictive model has the potential to serve as a decision-support tool. Further external validation is required before its integration into routine clinical practice.

Impact of deep inspiration breath hold irradiation on dose reduction to the heart and left coronary artery in breast cancer

Impact of deep inspiration breath hold irradiation on dose reduction to the heart and left coronary artery in breast cancer

Eliciting the views of left breast cancer patients' receiving deep inspiration breath hold radiation therapy to inform the design of multimedia education and improve patient-centred care for prospective patients.

The currently accepted best practice radiation treatment for left breast cancer patients is Deep Inspiration Breath Hold (DIBH) where patients hold a deep breath to reduce late cardiac and pulmonary effects from treatment. DIBH can be challenging and induce or exacerbate anxiety in patients due to the perceived pressure to reduce radiation treatment side effects. This study explored the experiences of patients treated with Deep Inspiration Breath Hold Radiation Therapy (DIBH-RT) to improve patient-centred care and inform the design of multimedia educational tools for future patients undergoing DIBH. This descriptive qualitative study was underpinned by a social constructivist approach to create new educational and patient care approaches based on previous patients' experiences. Semi-structured interviews were conducted with patients who had completed DIBH-RT for breast cancer. Data was analysed with reflexive thematical analysis. Twenty-two patients were interviewed with five key themes identified: (1) informational needs, (2) care needs, (3) autonomy, (4) DIBH performance influencers and (5) other centredness. Recommendations were derived from these themes to improve future treatments of DIBH patients. These recommendations revolved around improvements to education, patient-centred care and strategies to improve self-efficacy with breath holding. Patients offer a wealth of knowledge regarding their lived experiences with treatment which can enhance future patients' experiences if incorporated into their education and care. Eliciting patients' views of their DIBH-RT treatment highlighted the need to improve patient self-efficacy with DIBH through familiarity with their planned treatment from new multimedia education, and foster patient care to enhance their experience.

Skin marker combined with surface-guided auto-positioning for breast DIBH radiotherapy daily initial patient setup: An optimal schedule for both accuracy and efficiency.

By employing three surface-guided radiotherapy (SGRT)-assisted positioning methods, we conducted a prospective study of patients undergoing SGRT-based deep inspiration breath-hold (DIBH) radiotherapy using a Sentine/Catalys system. The aim of this study was to optimize the initial positioning workflow of SGRT-DIBH radiotherapy for breast cancer. A total of 124 patients were divided into three groups to conduct a prospective comparative study of the setup accuracy and efficiency for the daily initial setup of SGRT-DIBH breast radiotherapy. Group A was subjected to skin marker plus SGRT verification, Group B underwent SGRT optical feedback plus auto-positioning, and Group C was subjected to skin marker plus SGRT auto-positioning. We evaluated setup accuracy and efficiency using cone-beam computed tomography (CBCT) verification data and the total setup time. In groups A, B, and C, the mean and standard deviation of the translational setup-error vectors were small, with the highest values of the three directions observed in group A (2.4±1.6, 2.9±1.8, and 2.8±2.1mm). The rotational vectors in group B (1.8±0.7°, 2.1±0.8°, and 1.8±0.7°) were significantly larger than those in groups A and C, and the Group C setup required the shortest amount of time, at 1.5±0.3min, while that of Group B took the longest time, at 2.6±0.9min. SGRT one-key calibration was found to be more suitable when followed by skin marker/tattoo and in-room laser positioning, establishing it as an optimal daily initial set-up protocol for breast DIBH radiotherapy. This modality also proved to be suitable for free-breathing breast cancer radiotherapy, and its widespread clinical use is recommended.

Surface-guided radiotherapy systems in locoregional deep inspiration breath hold radiotherapy for breast cancer - a multicenter study on the setup accuracy.

Daily image-guided radiotherapy (IGRT) and deep inspiration breath hold (DIBH) technique are recommended for locoregional RT of breast cancer. The optimal workflow for a combination of surface-guided RT (SGRT) with DIBH technique is of current clinical interest. The setup accuracy at three hospitals was evaluated using different SGRT workflows. A total of 150 patients (2269 image pairs) were analyzed in three groups: patient setup with the AlignRT® SGRT system in Tampere (Site 1, n = 50), the Catalyst™ SGRT system in Turku (Site 2, n = 50) and the Catalyst™ SGRT system in Jönköping (Site 3, n = 50). Each site used their routine workflow with SGRT-based setup and IGRT positioning. Residual errors of the bony chest wall, thoracic vertebra (Th 1) and humeral head were evaluated using IGRT images. Systematic residual errors in the cranio-caudal (CC) direction and in pitch were generally larger at Site 2 than those at Sites 1 and 3 (p = 0.01-0.7). With daily IGRT, only a small difference (p = 0.01-0.9) was observed in residual random errors of bony structures in other directions between sites. The introduction of SGRT and the use of daily IGRT lead to small residual errors when combining the best workflow practices from different hospitals. Our multicenter evaluation led to improved workflow by tightening the SGRT tolerances on Site 2 and fixation modification. Because of mainly small random errors, systematic posture errors in the images need to be corrected after posture correction with new setup surfaces. We recommend tight SGRT tolerances, good fixation and correction of systematic errors.

Protocol of a phase II study to evaluate the efficacy and safety of deep-inspiration breath-hold daily online adaptive radiotherapy for centrally located lung tumours (PUDDING study)

BackgroundCentrally located lung tumours present a challenge because of their tendency to exhibit symptoms such as airway obstruction, atelectasis, and bleeding. Surgical resection of these tumours often requires sacrificing the lungs, making definitive radiotherapy the preferred alternative to avoid pneumonectomy. However, the proximity of these tumours to mediastinal organs at risk increases the potential for severe adverse events. To mitigate this risk, we propose a dual-method approach: deep inspiration breath-hold (DIBH) radiotherapy combined with adaptive radiotherapy. The aim of this single-centre, single-arm phase II study is to investigate the efficacy and safety of DIBH daily online adaptive radiotherapy.MethodsPatients diagnosed with centrally located lung tumours according to the International Association for the Study of Lung Cancer recommendations, are enrolled and subjected to DIBH daily online adaptive radiotherapy. The primary endpoint is the one-year cumulative incidence of grade 3 or more severe adverse events, as classified by the Common Terminology Criteria for Adverse Events (CTCAE v5.0).DiscussionDelivering definitive radiotherapy for centrally located lung tumours presents a dilemma between ensuring optimal dose coverage for the planning target volume and the associated increased risk of adverse events. DIBH provides measurable dosimetric benefits by increasing the normal lung volume and distancing the tumour from critical mediastinal organs at risk, leading to reduced toxicity. DIBH adaptive radiotherapy has been proposed as an adjunct treatment option for abdominal and pelvic cancers. If the application of DIBH adaptive radiotherapy to centrally located lung tumours proves successful, this approach could shape future phase III trials and offer novel perspectives in lung tumour radiotherapy.Trial registration. Registered at the Japan Registry of Clinical Trials (jRCT; https://jrct.niph.go.jp/); registration number: jRCT1052230085 (https://jrct.niph.go.jp/en-latest-detail/jRCT1052230085).

Individual benefit in heart sparing during DIBH-supported left breast radiotherapy

IntroductionDeep-inspirational breath hold (DIBH) is an option for heart protection in breast radiotherapy; we intended to study its individual benefit. Materials and Methods3DCRT treatment planning was performed in a cohort of 103 patients receiving radiotherapy of the whole breast (WBI)/chest wall (CWI) ± nodal regions (NI) both under DIBH and free breathing (FB) in the supine position, and in the WBI only cases prone (n = 45) position, too. A series of patient-related and heart dosimetry parameters were analyzed. ResultsThe DIBH technique provided dramatic reduction of all heart dosimetry parameters the individual benefit, however, varied. In the whole population the best predictor of benefit was the ratio of ipsilateral lung volume (ILV)FB and ILVDIBH. In the WBI cohort 9–11 patients and 5–8 patients received less dose to selected heart structures with the DIBH and prone positioning, respectively; based on meeting various dose constraints DIBH was the only solution in 6–13 cases, and prone positioning in 5–6 cases. In addition to other excellent predictors, a small ILVFB or ILVDIBH with outstanding predicting performance (AUC ≥ 0.90) suggested prone positioning. Detailed analysis consistently indicated the outstanding performance of ILVFB and ILVDIBH in predicting the benefit of one over the other technique in lowering the mean heart dose (MHD), left anterior descending coronary artery (LAD) mean dose and left ventricle(LV)-V5Gy. The preference of prone positioning was further confirmed by anatomical parameters measured on a single CT scan at the middle of the heart. Performing spirometry in a cohort of 12 patients, vital capacity showed the strongest correlation with ILVFB and ILVDIBH hence this test could be evaluated as a clinical tool for patient selection. DiscussionIndividual lung volume measures estimated by spirometry and anatomical data examined prior to acquiring planning CT may support the preference of DIBH or prone radiotherapy for optimal heart protection.

Continuous Positive Airway Pressure–Assisted Breathing With Supine Tangential Left Breast Radiation Therapy When Deep Inspiration Breath-Hold Radiation Therapy Was Ineffective or Unsuitable: Clinical Implications for an Affordable Heart-Sparing Breast Radiation Therapy to Reduce the Health Care Disparities in Low-Resource Settings

Continuous Positive Airway Pressure–Assisted Breathing With Supine Tangential Left Breast Radiation Therapy When Deep Inspiration Breath-Hold Radiation Therapy Was Ineffective or Unsuitable: Clinical Implications for an Affordable Heart-Sparing Breast Radiation Therapy to Reduce the Health Care Disparities in Low-Resource Settings

Deep inspiration breath hold real-time tumor-tracking radiation therapy (DBRT) as a novel stereotactic body radiation therapy approach for lung tumors

Radiotherapy with deep inspiration breath hold (DIBH) reduces doses to the lungs and organs at risk. The stability of breath holding and reproducibility of tumor location are higher during expiration than during inspiration; therefore, we developed an irradiation method combining DIBH and real-time tumor-tracking radiotherapy (RTRT) (DBRT). Nine patients were enrolled in this study. Fiducial markers were placed near tumors using bronchoscopy. Treatment planning computed tomography (CT) was performed thrice during DIBH, assisted by spirometer-based device. Each CT scan was fused using fiducial markers. Gross tumor volume (GTV) was contoured for each dataset and summed to create GTVsum; adding a 5-mm margin around GTVsum generated the planning target volume. The prescribed dose was mainly 42 Gy in four fractions. The treatment plan was created using DIBH CT (DBRT-plan), with a similar treatment plan created for expiratory CT for cases for which DBRT could not be performed (conv-plan). Vx defined as the volume of the lung received x Gy, and the mean lung dose, V20, V10, and V5 were evaluated. DBRT was completed in all patients. Mean dose, V20, and V10 were significantly lower in the DBRT-plan than in the conv-plan (all p = 0.003). Mean rates of decrease for mean dose, V20, and V10 were 14.0%, 27.6%, and 19.1%, respectively. No significant difference was observed in V5. We developed DBRT, a stereotactic body radiation therapy performed with the DIBH technique; it combines a spirometer-based breath-hold support system with an RTRT system. All patients who underwent DBRT completed the procedure without any technical or mechanical complications. This is a promising methodology that may significantly reduce lung doses.

Chest Wall to Heart Distance Reproducibility in Postoperative Deep Inspiration Breath-Hold Radiotherapy for Left-Sided Breast Cancer Using an Anzai Laser Sensor With Visual Feedback.

Background Left-sided breast cancer radiotherapy may increase the risk of cardiovascular death due to possible heart irradiation. Thereproducibility of the chest wall to heart distance in deep inspiration breath-hold (DIBH) was studied using a laser sensor with visual feedback. Methodology A total of 10 consecutive postoperative left-sided breast cancer cases receiving DIBH radiotherapy between December 2022 and September 2023 were retrospectively investigated. The prescribed dose was 50 Gy in 25 fractions. An Anzai respiratory gating system, AZ-733VI (Anzai, Tokyo, Japan), was employed that has a laser displacement sensor and a visual feedback device. An Elekta linac with a cone-beam CT unit, Axesse (Elekta AB, Stockholm, Sweden), was used in this study. The interfractional changes in the chest wall to heart distance among 25 fractions were analyzed for each of the 10 patients in each coordinate axis. In addition, the median with the 95% confidence interval (CI) and interquartile range (IQR) for all 250 fractions were calculated in each axis to assess the reproducibility of our DIBH technique. Results The medians of the interfractional changes in the chest wall to heart distance in each of the 10 patients ranged from -2 mm to 3 mm, -1 mm to 3 mm, and -2 mm to 1 mm in the lateral (X), superior-inferior (Y), and anterior-posterior (Z) directions, respectively. For all 10 cases, the medians were 1 mm (95% CI = 0.72 to 1.28 mm) in X, 1 mm (95% CI = 0.76 to 1.24 mm) in Y, and 0 mm (95% CI = -0.20 to 0.20 mm) in Z directions, whereas the IQRs were 4 mm in X, 2 mm in Y and 2 mm in Z directions. The measured IQRs were two to three times smaller than those shown in a previous report without visual feedback, suggesting a clinical advantage of the visual feedback in DIBH for left-sided breast cancer radiotherapy. The DIBH solution shown in this study required approximately 10 minutes from room-in to room-out, thereby not reducing the daily number of patients. Conclusions Our DIBH approach with visual feedback achieved better distance reproducibility between the chest wall and heart by a factor of two to three in terms of IQR compared to the previously reported data without visual feedback. Patient throughput was also favorable. To our knowledge, this is the first report demonstrating the chest wall to heart distance reproducibility in DIBH with visual feedback.

Cardiac segments dosimetric benefit from deep inspiration breath hold technique for left-sided breast cancer radiotherapy.

The objective was to compare dosimetry in left-sided breast cancer (LSBC) patients receiving deep inspiration breath hold (DIBH) radiotherapy (RT) with free-breathing (FB) treatment plans. Voluntary DIBH with a spirometer-based video-assisted system and CT-simulation were performed under FB and DIBH conditions on 40 LSBC patients, segmented according Duane's atlas. IMRT plans kept the same dosimetric goals on FB and DIBH conditions. Target, lungs and heart volumes were measured. Planning target volume (PTV) dose distribution, organs at risk (OARs) dose/volume parameters, including cardiac substructures, were calculated. Lungs and left-lung volumes increased in DIBH conditions (ΔV = 1637.8 ml ± 555.3 and 783.5 ml ± 286.4, respectively). Heart volume slightly decreased in apnea (p = 0.04), but target volumes, CTV and PTV were similar in FB or DIBH plans. PTV dose coverage was similar irrespective of respiratory conditions (median D50% = 41.1 Gy vs 41.0 Gy, p = 0.665; V95% = 96.9% vs. 97%). Mean dose for the whole heart (MHD), left ventricle (LV), and LV segments were significantly reduced in DIBH plans. V20 values for heart subvolumes were significantly different only for those that received considerable doses (apical and anterior). DIBH plans provided significantly smaller doses (Dmax, D2%, and V20) to the LAD artery. Important dosimetric improvements can be achieved with DIBH technique for LSBC patients, reducing the dose to the LAD artery and heart, particularly to the segments closer to the chest wall. Apical/anterior LV segments, should be considered as separate organ at risk in breast RT.

Failure mode and effects analysis in consensus-based GDM for surface-guided deep inspiration breath-hold breast radiotherapy for breast cancer under the framework of linguistic Z-number

Most of the cancer patients cannot get the usual treatment in the advanced stage of the disease. In particular, for breast cancer, it is to use a special kind of radiation that targets the tumor while the patient holds their breath. This is called surface-guided (SG) breast radiotherapy (RT) with deep inspiration breath-hold (DIBH). This treatment is very complicated and different from the normal way of treating breast cancer. It can also have many errors and problems that are not well-studied or understood. To prevent these problems, we need to use a method called failure mode and effects analysis (FMEA). This method helps us find and rank the possible risks and how to avoid them. In keeping with this aim, this paper studies consensus-reaching process-based group decision-making (GDM) with completely unknown risk factors' weights and the gained-lost dominance score (GLDS)-based ranking process. We cannot avoid the uncertainty related to relativity information in medical science. Therefore, in this study, we offer the experts to provide their opinions using the linguistic Z number (LZN) because LZN is designed to capture such types of information in medical science. For the consensus-reaching process (CRP), the relativity among experts is considered for consensus measurement, and the minimum adjustment sum with group consensus opinion-based feedback is offered. For unknown weight of risk factors, we don't know how much each risk factor weighs. So, we use a method that combines two ways of calculating weights. One way is a subjective weight computation process, and the other way is based on the data using entropy and division. Finally, we applied our proposed CRP-based GDM approach for ranking the identified FMs related to the SG DIBH RT process. We conduct sensitive, comparative, and statistical assessments to ensure our method is reasonable and practical.

AI segmentation as a quality improvement tool in radiotherapy planning for breast cancer

AI segmentation has been recently introduced in the local department for delineation of targets and organs-at-risk (OAR) for a wide range of tumour sites. For breast radiotherapy, AI segmentation can provide target delineation (breast and lymph nodes) and required OAR, and this has enabled a stepwise series of improvements to the local planning technique.Clinician feedback deemed 67 - 89 % of nodal target volumes required no edits or only minor edits, so AI breast and lymph nodes volumes were first used to guide tangent and supraclavicular field placement, instead of a bony-anatomy based technique.Next, evolution from anatomical field-placement to true inverse optimised planning was introduced using AI to create the required target volumes. For internal mammary node (IMN) treatments, the previous 3-field technique prohibited Deep Inspiration breath-hold (DIBH), due to the couch rotation used to match field edges. The roll-out of VMAT (volumetric-modulated arc therapy) with DIBH enabled by AI therefore resulted in a dose reduction to ipsi-lateral lung, and in mean heart dose compared to the old 3-field technique. Median time from CT scan to VMAT IMN plan approval reduced from 12 days (with manual contouring) to 7 days using reviewed and edited AI-generated volumes.Consistent, high-quality contours for 9 OAR and breast PTVs for all patients facilitates comparison with NHS-E scorecards as a benchmark for plan quality. Workflows have been simplified, with significant time-savings. DIBH radiotherapy is now available to more patients, further improving dose sparing for heart and lung.

EP08.02-32 Optimal Planning Target Volume Margins for Spirometer-Based DIBH Radiotherapy for Lung Cancer

EP08.02-32 Optimal Planning Target Volume Margins for Spirometer-Based DIBH Radiotherapy for Lung Cancer

The Effect of Deep Inspiration Breath-Hold Technique on Right Coronary Artery, Heart, and Liver Doses in Right Breast Cancer Radiotherapy

The deep inspiration breath-hold (DIBH) approach has been thoroughly researched with the aim of reducing radiation exposures to normal tissues in breast cancer patients. Although heart and lung toxicity are widely addressed in many literature, radiation-associated liver toxicity and dose constraints for the right coronary artery (RCA) are not well studied in relation to breast radiotherapy. Additionally, very few studies have investigated the relationship between doses to cardiac substructures. This study aimed to determine the effect of the DIBH technique on the right coronary artery (RCA) region, cardiac substructures, and liver dose in right breast cancer irradiation. Between January 2022 and December 2022, thirty-five right breast cancer patients who previously received breast-surgery underwent computed tomography (CT) simulation with both free-breathing (FB) and DIBH techniques. Patients were contoured by a radiation oncologist on the scans using the Treatment Planning System. For cardiac substructures, reference atlas contours were used for accurate delineation and to reduce inter-observer variation. Each patient underwent two treatment plans for both the DIBH and FB datasets. The plan comprised the FB and DIBH techniques, and the doses to the cardiac substructures, ipsilateral lung, RCA region, and liver were compared using a two-tailed paired t-test. Radiotherapy was delivered with a Linac with the prescription dose of 50 Gy in 25 fractions. For both FB and DIBH irradiation groups, the mean radiation doses to the ipsilateral lung, heart, and RCA region in patients with FB and DIBH techniques were; 14.67 Gy, 2.33 Gy, 4.88 Gy and 12.05 Gy, 1.34 Gy and 3.29 Gy respectively. The mean radiation doses to the cardiac substructures; for the left ventricle, right ventricle, left atrium, and right atrium for the FB were 1.08 Gy, 1.79 Gy, 4.11 Gy, and for DIBH, 0.49 Gy, 1.49 Gy, 0.95 Gy, and 2.61 Gy, respectively. For the DIBH group, the liver maximum dose (p<0.01), right lung mean dose (p = 0.001), heart maximum dose (p = 0.009), RCA mean dose (p = 0.020), RCA maximum dose (p = 0.008), RCA V5 dose (p = 0.035), right atrium maximum dose (p = 0.009) and right ventricle mean dose (p = 0.040) were significantly lower than in patients treated in the non-gated group. DIBH resulted in considerable displacement of the liver away from the high-dose target region, such that the volume of liver in the high-dose region was reduced. Additionally, the use of the DIBH technique in right breast cancer irradiation effectively reduces the radiation doses to the cardiac substructures, such as the left ventricle, right ventricle, left atrium, right atrium, RCA region, and lungs. DIBH could lead to substantial sparing of these structures with the right breast cancer radiotherapy. Future prospective studies are required to determine whether improvements to dose-distribution will translate into improved toxicity outcomes.

Application of tangent-arc technology for deep inspiration breath-hold radiotherapy in left-sided breast cancer.

To explore the advantages of dosimetry and the treatment efficiency of tangent-arc technology in deep inspiration breath-hold radiotherapy for breast cancer. Forty patients with left-sided breast cancer who were treated in our hospital from May 2020 to June 2021 were randomly selected and divided into two groups. The first group's plan was a continuous semi-arc that started at 145° ( ± 5°) and stopped at 325° ( ± 5°). The other group's plan, defined as the tangent-arc plan, had two arcs: the first arc started at 145° ( ± 5°) and stopped at 85° ( ± 5°), and the second arc started at 25° ( ± 5°) and stopped at 325° ( ± 5°). We compared the target dose, dose in organs at risk (OARs), and treatment time between the two groups. The target dose was similar between the continuous semiarc and tangent-arc groups. The V5 of the right lung was significantly different between the two groups (Dif 5.52, 95% confidence interval 1.92-9.13, t=3.10, P=0.004), with the patients in the continuous semi-arc and tangent-arc groups having lung V5 values of (9.16 ± 1.62)%, and (3.64 ± 0.73)%, respectively. The maximum dose to the spinal cord was (1835.88 ± 222.17) cGy in the continuous semi-arc group and (599.42 ± 153.91) cGy in the tangent-arc group, yielding a significant difference between the two groups (Dif 1236.46, 95% confidence interval 689.32-1783.6, t=4.57, P<0.001). The treatment times was (311.70 ± 60.45) s for patients in the continuous semi-arc group and (254.66 ± 40.73) s for patients in the tangent-arc group, and there was a significant difference in the mean number of treatment times between the two groups (Dif 57.04, 95% confidence interval 24.05-90.03, t=3.5, P=0.001). Both the continuous semi-arc and tangent-arc plans met the clinical prescription dose requirements. The OARs received less radiation with the tangent-arc plan than the continuous semi-arc plan, especially for the lung (measured as V5) and the spinal cord (measured as the maximum dose). Tangent-arc plan took significantly less time than the continuous semi-arc, which can greatly improve treatment efficiency. Therefore, tangent-arc plans are superior continuous semi-arc plans for all cases.

Comparison of cone beam computed tomography (CBCT)-based image guided radiotherapy approaches in the reduction of setup uncertainties during deep inspiration breath-hold radiotherapy (DIBH-RT) for left breast cancer

Advances in radiotherapy has allowed higher cure rates for cancer such as breast and thus, it is important to reduce the possible radiation side effects from exposure to other organs such as the heart. Deep inspiration breath-hold radiotherapy technique (DIBH-RT) significantly reduces cardiac dose during left breast radiotherapy, but the patient setup requires careful adoption of image guidance radiotherapy technique (IGRT) approaches. This study investigates the effectiveness of cone beam computed tomography (CBCT)-based IGRT protocols for patients' inter-fraction set-up correction. Setup error data from two patients’ groups; A and B who had daily CBCT and first 3 fractions + weekly CBCT imaging respectively, were analysed. This constitutes a total of 13 left breast cancer patients treated using DIBH-RT at Advanced Medical Dental Institute (AMDI), Universiti Sains Malaysia (USM), Malaysia. The analysis was performed using MATLAB (MathWorks Inc Natick MA) to calculate the mean setup errors. The population systematic (∑) and random (σ) errors were calculated for non-IGRT, online, and two offline IGRT protocols; no action level (NAL) and extended no action level (eNAL) for each patient group. The corresponding planning target volume (PTV) margin and its percentage reduction for each of the IGRT protocols were established using van Herk margin recipe. The least population systematic setup error and PTV margin were found when using the online protocol (∑X/Y/Z = 0.17/0.22/0.31 mm; PTVX/Y/Z = 0.71/0.92/1.28 mm) followed by eNAL (∑X/Y/Z = 1.32/1.94/1.85 mm; PTVX/Y/Z = 5.75/7.99/8.46 mm), NAL (∑X/Y/Z = 1.45/2.26/1.84 mm; PTVX/Y/Z = 6.27/8.93/8.46 mm) and non-IGRT (∑X/Y/Z = 2.28/3.35/3.10 mm; PTVX/Y/Z = 7.77/10.85/10.93 mm). Up to 90% in PTV margin reduction is achieved with the online protocol. In conclusion, the use of IGRT during DIBH-RT for left breast cancer patients reduces patient set-up error and allows the use of tighter PTV margins. The online IGRT protocol was shown to be more effective in the reduction of errors and the PTV margin followed by eNAL and NAL offline IGRT protocols.