Radiotherapy For Breast Cancer Research Articles

Quality of Life Outcomes Associated With Optimization of Treatment by Omitting Radiotherapy in Early Breast Cancer

PurposeImproved prognosis of early breast cancer (EBC) has created opportunities for treatment optimization but reducing morbidity should not inadvertently compromise quality of life (QoL). PROSPECT1 used pre-operative MRI and pathology findings to identify women suitable for radiotherapy (RT) omission following breast conserving surgery. We retrospectively explored the association between de-escalation by omission of RT and QoL in women with EBC. Materials and methodsThree groups were recruited: PROSPECT participants who omitted RT following preoperative MRI (A); participants who received RT following preoperative MRI (B); and women who received usual care - No MRI, received RT (C). Measures included the EORTC QLQ-C30 and BR23, BCTOS, DASS-21 and a measure of decision regret. Between group differences were assessed using ANOVA or nonparametric equivalents. Semi-structured interviews were analyzed with qualitative description (n = 44). ResultsData from 400 women were analyzed (125A, 102B, 173C). Group A had fewer symptoms and better body image (breast symptoms: A-B P = .003, A-C P = <.001; arm symptoms: A-B P = .004, A-C P = .011; body image: A-C P = .041) and fewer differences between the treated and untreated breasts (cosmetic: A-B P < .001, A-C P < .001; functional: A-C P = .011; breast specific pain: A-B P < .001, A-C P < .001). Two qualitative themes were found: Treatment with the biggest impact on QoL, and Specific impact of RT on QoL. ConclusionsOmission of RT was associated with better QoL and functional and cosmetic outcomes. It was highly acceptable to patients. Clinicians should consider the potential for preserved QoL associated with treatment optimization via omission of RT in treatment planning for patients with EBC.

151 (PB-058) Poster - Predictive factors of incidental internal mammary chain irradiation in breast cancer radiotherapy

151 (PB-058) Poster - Predictive factors of incidental internal mammary chain irradiation in breast cancer radiotherapy

Effects on Lung Tissue After Breast Cancer Radiation: Comparing Photon and Proton Therapies

PurposeIn breast cancer, improved treatment approaches that reduce injury to lung tissue and early diagnosis and intervention for lung toxicity are increasingly important in survivorship. The aims of this study are to (1) compare lung tissue radiographic changes in women treated with conventional photon radiation therapy and those treated with proton therapy (PT), (2) assess the volume of lung irradiated to 5 Gy (V5) and 20 Gy (V20) by treatment modality, and (3) quantify the effects of V5, V20, time, and smoking history on the severity of tissue radiographic changes. Patients and MethodsA prospective observational study of female breast cancer patients was conducted to monitor postradiation subclinical lung tissue radiographic changes. Repeated follow-up x-ray computed tomography scans were acquired through 2 years after treatment. In-house software was used to quantify an internally normalized measure of pulmonary tissue density change over time from the computed tomography scans, emphasizing the 6- and 12-month time points. ResultsCompared with photon therapy, PT was associated with significantly lower lung V5 and V20. Lung V20 (but not V5) correlated significantly with increased subclinical lung tissue radiographic changes 6 months after treatment, and neither correlated with lung effects at 12 months. Significant lung tissue density changes were present in photon therapy patients at 6 and 12 months but not in PT patients. Significant lung tissue density change persisted at 12 months in ever-smokers but not in never-smokers. ConclusionPatients treated with PT had significantly lower radiation exposure to the lungs and less statistically significant tissue density change, suggesting decreased injury and/or improved recovery compared to photon therapy. These findings motivate additional studies in larger, randomized, and more diverse cohorts to further investigate the contributions of treatment modality and smoking regarding the short- and long-term radiographic effects of radiation on lung tissue.

143 (PB-050) Poster - MR-guided adaptive partial breast radiotherapy in low-risk breast cancer: a phase II study

143 (PB-050) Poster - MR-guided adaptive partial breast radiotherapy in low-risk breast cancer: a phase II study

23 (PB-4) Poster Spotlight - Development of an explainable AI prediction model for arm lymphoedema following breast cancer surgery and radiotherapy

23 (PB-4) Poster Spotlight - Development of an explainable AI prediction model for arm lymphoedema following breast cancer surgery and radiotherapy

Lymphocytopenia following adjuvant radiotherapy for breast cancer

AbstractObjectiveWe retrospectively analyzed breast cancer patients who received adjuvant radiotherapy to determine the incidence of lymphocytopenia and its risk factors.MethodsWe reviewed 812 patients with breast cancer who received postoperative radiotherapy. Patients were divided into two groups based on the use of chemotherapy, and a generalized linear regression model was used to explore predictive factors for grade 2 or higher lymphocytopenia. We also examined the effect of lymphocytopenia on overall survival.ResultsGrade 2 or higher lymphocytopenia was observed in 19.4% of patients who did not receive chemotherapy and 45.1% of patients who received chemotherapy. In multivariate analysis, bilateral disease, regional lymph node irradiation, and baseline lymphocytopenia were associated with lymphocytopenia in patients who did not receive cytotoxic chemotherapy. Regional lymph node irradiation, baseline lymphocytopenia, use of antimetabolites, and use of molecular‐targeted agents were associated with lymphocytopenia in patients treated with chemotherapy. In the survival analysis, lymphocytopenia was associated with worse overall survival only in patients treated with cytotoxic chemotherapy (p = 0.039), and not in patients who did not receive chemotherapy (p = 0.77).ConclusionThe analysis revealed the incidence and risk factors of lymphocytopenia after postoperative radiotherapy in patients with breast cancer.

Clinical Feasibility of Artificial Intelligence-Based Autosegmentation of the Left Anterior Descending Artery in Radiotherapy for Breast Cancer

Abstract Introduction Breast cancer is a prevalent global disease, and radiotherapy plays a crucial role in its treatment. However, radiotherapy may lead to cardiac complications, particularly in patients receiving left-sided radiotherapy who may experience increased risks due to toxicity in the left anterior descending (LAD) artery. The manual contouring of the LAD artery is time-consuming and subject to variability. This study aimed to provide an overview of artificial intelligence (AI) based LAD artery contouring, assess its feasibility, and identify its limitations. Objectives The primary objectives were to evaluate the feasibility of AI-based LAD artery contouring, compare different approaches, and quantify properties impacting accuracy. The secondary objective was to recommend algorithms with greater accuracy. Materials and Methods A (noncontrast) computed tomography dataset of nine patients with breast cancer was used to analyze the features and behavior of the LAD artery. The functioning of different AI models used for autosegmentation was studied, and the LAD artery imaging features were identified and quantified using the widely used AI models. Additionally, an algorithm to reliably compute interpatient variability in the LAD artery contours was proposed. Results A lack of distinctive features, diminutive contour size (∼5 pixels on average), and inconsistent position of the LAD artery were observed. The interpatient variability in the LAD artery contours was five to seven times the average size of the contours. The dataset also had a high standard deviation of 28.9 and skewed data distribution. Conclusions The results indicated that the variable path of the LAD artery and high interpatient variability were the primary reasons for the inability of AI algorithms to have a concordance. Further, the small contour size amplified model inaccuracy. For higher autosegmentation accuracy, an anatomical landmark–based approach is necessary to capture surrounding structures that affect the path of the LAD artery.

Comparing Performances of Predictive Models of Toxicity after Radiotherapy for Breast Cancer Using Different Machine Learning Approaches.

Different ML models were compared to predict toxicity in RT on a large cohort (n = 1314). The endpoint was RTOG G2/G3 acute toxicity, resulting in 204/1314 patients with the event. The dataset, including 25 clinical, anatomical, and dosimetric features, was split into 984 for training and 330 for internal tests. The dataset was standardized; features with a high p-value at univariate LR and with Spearman ρ>0.8 were excluded; synthesized data of the minority were generated to compensate for class imbalance. Twelve ML methods were considered. Model optimization and sequential backward selection were run to choose the best models with a parsimonious feature number. Finally, feature importance was derived for every model. The model's performance was compared on a training-test dataset over different metrics: the best performance model was LightGBM. Logistic regression with three variables (LR3) selected via bootstrapping showed performances similar to the best-performing models. The AUC of test data is slightly above 0.65 for the best models (highest value: 0.662 with LightGBM). No model performed the best for all metrics: more complex ML models had better performances; however, models with just three features showed performances comparable to the best models using many (n = 13-19) features.

The Development and Evaluation of an Educational Video for Breast Cancer Patients Requiring Adjuvant Radiation Therapy

Patient education and informed consent are required prior to adjuvant radiation therapy (RT) for early breast cancer (EBC), and include the role, rationale, potential toxicities and practicalities of the treatment process. Current education of patients about RT is verbal, in the form of a consultation by a radiation oncologist, often supplemented with print or online materials. This approach is limited by its doctor-dependency and non-standardised nature. Video education is being recognised increasingly as an opportunity to remediate this and appeal to patients’ preference for visual learning. The purpose of this study was to design and produce a video as an educational adjunct for EBC patients’ viewing prior to adjuvant RT, and to evaluate its acceptability through content analysis of three online focus group discussions, among ten participants with EBC requiring RT. After qualitative content analysis of the focus group transcripts, data were summarised into three main categories: (1) understanding of RT, (2) ease of engagement with the video and (3) anxiety and preparedness for RT. The 18-min video was positively received by all participants, and discussion feedback was used to inform improvements to the video. This focus group study demonstrated that the video was well understood, informative and acceptable to EBC patients in preparing them for RT. The effectiveness of the video in improving knowledge and alleviating distress in preparation for therapy will be further evaluated in an ethics-approved biphasic quasi-experimental study.

The Accessible Clinical Application Progress of Supine Fixation Technique in Radiotherapy After Breast Conserving Surgery for Early Breast Cancer in China

Radiation therapy (radiotherapy) is one of the important methods for comprehensive treatment of breast cancer. Radiotherapy after breast conserving surgery for early breast cancer can not only achieve local control rate and long-term survival rate similar to total mastectomy, but also meet patients&amp;apos; pursuit of higher quality of life. With the development of intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), helical tomotherapy (HT), and other advanced radiotherapy technique, the consistency of patient position fixation during radiotherapy is the key to ensure the implementation of accurate radiotherapy. Due to the special and high activity of breast organs, there is no unified fixation method for breast conserving postoperative radiotherapy. This article reviews the clinical application and research progress of various accessible supine fixation techniques in early breast cancer postoperative radiotherapy in recent years. This paper analyzes the clinical application method and clinical application effect of various techniques, compares the advantages and disadvantages of each technology. It is found that breast bracket is the most widely used for classical breast cancer radiotherapy. In any fixation technique, it is still a practical problem for the clinic to solve the problem of the normal location of the breast activity and the consistency of the radiation. It is recommended that the position of the supposition fixation technique should be selected according to the patient&amp;apos;s BMI, breast size and target area.

Organ-sparing techniques and dose-volume constrains used in breast cancer radiation therapy – Results from European and Latin American surveys

BackgroundAdvances in local and systemic therapies have improved the outcomes of patients with breast cancer (BC), leading to a possible increased risk for postoperative radiation therapy (RT) late adverse events. The most adequate technologies and dose constraints for organs at risk (OAR) in BC RT have yet to be defined. MethodsAn online survey was distributed to radiation oncologists (ROs) practicing in Europe and Latin America including the Caribbean (LAC) through personal contacts, RO and BC professional groups’ networks. Demographic data and clinical practice information were collected. ResultsThe study included 585 responses from ROs practicing in 57 different countries. The most frequently contoured OAR by European and LAC participants were the whole heart (96.6 % and 97.7 %), the ipsilateral (84.3 % and 90.8 %), and contralateral lung (71.3 % and 77.4 %), whole lung (69.8 % and 72.9 %), and the contralateral breast (66.4 % and. 83.2 %). ESTRO guidelines were preferred in Europe (33.3 %)and the RTOG contouring guideline was the most popular in LAC (62.2 %), while some participants used both recommendations (13.2 %and 19.2 %). IMRT (68.6 % and 59.1 %) and VMAT (65.6 % and 60.2 %) were the preferred modalities used in heart sparing strategies, followed by deep inspiration breath-hold (DIBH)(54.8 % and 37.4 %) and partial breast irradiation (PBI)(41.6 % and 24.6 %). Only a small percentage of all ROs reported the dose-volume constraints for OAR used in routine clinical practice. A mean heart dose (Heart-Dmean) between 4 and 5 Gy was the most frequently reported parameter (17.2 % and 39.3 %). ConclusionThe delineation approaches and sparing techniques for OAR in BC RT vary between ROs worldwide. The low response rate to the dose constraints subset of queries reflects the uncertainty surrounding this topic and supports the need for detailed consensus recommendations in the clinical practice.

Dosimetric Comparison of CPAP and DIBH for Left-sided Breast Cancer Radiation Therapy

PurposeDespite the increasing interest in using continuous positive airway pressure (CPAP) in radiotherapy (RT), direct comparisons with the more widely employed deep inspiration breath-hold (DIBH) have been limited. This planning study aimed to offer comprehensive geometric and dosimetric evidence by comparing CPAP and DIBH-based RT plans. Materials and MethodsA retrospective dataset of 35 left-sided breast cancer patients with planning CT (pCT) scans under three breathing conditions (free breathing, CPAP with 10 cmH2O pressure, and DIBH) was collected. Volumetric arc therapy plans aimed for 95% dose coverage to 95% of the planning target volume with a maximum dose below 107%. A comparative dosimetric analysis among the three plans was conducted. Additionally, geometric differences were assessed by calculating the minimum distance between the heart and the clinical target volume (CTV) in each pCT. ResultsCPAP and DIBH plans demonstrated comparable mean heart doses (1.05 Gy), which were significantly lower than the FB plan (1.34 Gy). The maximum dose to the left anterior descending artery was smallest in the CPAP plan (4.44 Gy), followed by DIBH (4.73 Gy) and FB (7.33 Gy). Other organ-at-risk doses for CPAP and DIBH were similar, with mean contralateral breast doses of 2.27 and 2.21 Gy, mean ipsilateral lung doses of 4.09 and 4.08 Gy, V20 at 6.11 and 6.31%, and mean contralateral lung doses of 0.94 and 0.92 Gy, respectively. No significant difference was found in the minimum heart-to-CTV distance between CPAP and DIBH. DIBH exhibited the greatest lung volume (3908 cc), followed by CPAP (3509 cc), and FB (2703 cc). ConclusionThe comparison between CPAP and DIBH shows their similarity in both geometric and dosimetric aspects, providing strong evidence for CPAP's effectiveness and feasibility in RT. This suggests its potential as an alternative to DIBH for left-sided breast cancer patients.

Sleep quality and psychological disorders in breast cancer female patients receiving radiotherapy at a tertiary oncology center in West Saudi Arabia.

Breast cancer is the most prevalent type of cancer among women worldwide. Many recently diagnosed and treated breast cancer patients complain about sleep disorders, depression, anxiety, stress, and fatigue. This study aimed to evaluate sleep quality among breast cancer patients and to assess its association with psychological disorders, and socio-demographic and clinical characteristics of patients. This cross-sectional study was conducted among women who received radiotherapy for breast cancer (stage 1-3) at King Abdul-Aziz Medical City-Jeddah from January to August 2021. Each participant completed a personal information form, the Pittsburgh Sleep Quality Index (PSQI), the Depression, Anxiety, and Stress Scale-21 (DASS-21), and the International Physical Activity Questionnaire (IPAQ). Clinical data were collected from the medical records to evaluate certain risk factors. Descriptive statistics were used for participant characteristics, and analyses of variance were used to assess associations between the qualitative variables. Fifty-six women with a mean age of 50.1years and an average of 10months after cancer diagnosis were included. Poor sleep quality was present in 58% of respondents. Symptomatic depression, anxiety, and stress were found in 34%, 32%, and 30% of women, respectively. Poor sleep quality was associated with depression (p = 0.031), anxiety (p = 0.03), and stress (p = 0.024) and was independently associated with hot flashes. In multivariate analysis, patients with depression or withcancer for more than 6months were less likely to have good sleep after controlling other variables (21.74 and 14.71 times, respectively). Poor sleep quality was present in 58% of women with breast cancer receiving radiotherapy and was significantly associated with depression, anxiety, stress, and hot flashes. Depression level and cancer duration were significant predictors of sleep quality. Early identification and proper management of psychological and sleep disorders are necessary to improve the quality of life and survival of breast cancer patients.

Evaluating delivered radiation dose in intraoperative radiotherapy for breast cancer using TLD

The extra radiation that it delivers has been questioned by patients, physicians, and the public for early breast cancer patients of intraoperative radiotherapy (IORT). This investigation concerns a left breast Rando phantom with a lumpectomy cavity of 30 cm3 of left breast of Rando phantom made of polymethylmethacrylate (PMMA). Thermoluminescent dosimetry (TLD) was used to evaluate the extra radiation dose or air kerma (kair) rate under IORT from 20 Gy, 50 kV of an Xoft Axxent system. TLDs were first calibrated using 50 kV photons, and then inserted at phantom positions that were close to the positions of the represented organs and tissues. Equivalent doses (DT) delivered to the organ at risks (OAR) were evaluated according to ICRP 103. Entrance surface doses (ESD) or skin doses (Dskin) varied markedly among positions close to the lumpectomy cavity. The dose was 20 Gy at the surface of a balloon applicator and kair varied from 6.40 ± 0.92 Gy down to 1.20 ± 0.30 mGy along the left-right axis of the 17th slice of Rando. These experimental results are compared with those in the literature. The shielding effect of the tungsten-impregnated rubber was also evaluated. This study supports recommendations to patients, relatives, physicians and radiologists concerning IORT.

21-gene recurrence score in predicting the outcome of postoperative radiotherapy in T1-2N1 luminal breast cancer after breast-conserving surgery

BackgroundIn those with one to three positive lymph nodes (N1) breast cancer (BC), the 21-gene recurrence score (RS) classification can be referred for decision-making on adjuvant chemotherapy. This study aimed to investigate the effect of RS in predicting the survival benefit of postoperative radiotherapy (PORT) in T1-2N1 BC with estrogen receptor-positive and human epidermal growth factor receptor 2-negative disease after breast-conserving surgery (BCS). MethodsWe included patients with BC and available RS data from the Surveillance, Epidemiology, and End Results Oncotype DX database. The chi-square test, Kaplan-Meier method, propensity score matching (PSM) as well as multivariable Cox proportional hazard analyses were used for statistical analyses. ResultsWe included 6509 patients in the analysis. Of these patients, 5302 (85.5%) were treated with BCS + PORT, and 207 (15.5%) had BCS alone. There were 1419 (21.8%), 4319 (66.4%), and 771 (11.8%) patients being low-, intermediate-, and high-risk RS, respectively. After PSM, PORT was significantly associated with a 5-year overall survival (OS) advantage (95.1% vs. 90.5%, P < 0.001) compared to those without PORT, which similar breast cancer-specific survival (BCSS) was found between the treatment arms (P = 0.126). The sensitivity analyses showed that PORT was not associated with a better BCSS (P = 0.472) and OS (P = 0.650) than those without PORT in the low-risk RS cohort. However, PORT was associated with a better BCSS (P = 0.031) and OS (P < 0.001) compared to those without PORT in the intermediate/high-risk RS cohorts. ConclusionsOur study highlights the possible role of the RS in predicting the outcome of PORT in T1-2N1 luminal BC patients undergoing BCS.

Hyperbaric Oxygen Therapy and Late Local Toxic Effects in Patients With Irradiated Breast Cancer

Hyperbaric oxygen therapy (HBOT) is proposed as treatment for late local toxic effects after breast irradiation. Strong evidence of effectiveness is lacking. To assess effectiveness of HBOT for late local toxic effects in women who received adjuvant radiotherapy for breast cancer. This was a hospital-based, pragmatic, 2-arm, randomized clinical trial nested within the prospective UMBRELLA cohort following the trials within cohorts design in the Netherlands. Participants included 189 women with patient-reported moderate or severe breast, chest wall, and/or shoulder pain in combination with mild, moderate, or severe edema, fibrosis, or movement restriction 12 months or longer after breast irradiation. Data analysis was performed from May to September 2023. Receipt of 30 to 40 HBOT sessions over a period of 6 to 8 consecutive weeks. Breast, chest wall, and/or shoulder pain 6 months postrandomization measured by the European Organization for Research and Treatment of Cancer QLQ-BR23 questionnaire. Secondary end points were patient-reported fibrosis, edema, movement restriction, and overall quality of life. Data were analyzed according to intention-to-treat (ITT) and complier average causal effect (CACE) principles. Between November 2019 and August 2022, 125 women (median [range] age at randomization, 56 [37-85] years) with late local toxic effects were offered to undergo HBOT (intervention arm), and 61 women (median [range] age at randomization, 60 [36-80] years) were randomized to the control arm. Of those offered HBOT, 31 (25%) accepted and completed treatment. The most common reason for not accepting HBOT was high treatment intensity. In ITT, moderate or severe pain at follow-up was reported by 58 of 115 women (50%) in the intervention arm and 32 of 52 women (62%) in the control arm (odds ratio [OR], 0.63; 95% CI, 0.32-1.23; P = .18). In CACE, the proportion of women reporting moderate or severe pain at follow-up was 32% (10 of 31) among those completing HBOT and 75% (9.7 of 12.9) among control participants expected to complete HBOT if offered (adjusted OR, 0.34; 95% CI, 0.15-0.80; P = .01). In ITT, moderate or severe fibrosis was reported by 35 of 107 (33%) in the intervention arm and 25 of 49 (51%) in the control arm (OR, 0.36; 95% CI, 0.15-0.81; P = .02). There were no significant differences in breast edema, movement restriction, and quality of life between groups in ITT and CACE. In this randomized clinical trial, offering HBOT to women with late local toxic effects was not effective for reducing pain, but was effective for reducing fibrosis. In the subgroup of women who completed HBOT, a significant reduction in pain and fibrosis was observed. A smaller than anticipated proportion of women with late local toxic effects was prepared to undergo HBOT. ClinicalTrials.gov Identifier: NCT04193722.

P 012: Complete heart block following radiotherapy for breast cancer: A case report

P 012: Complete heart block following radiotherapy for breast cancer: A case report

Abstract A082: Stretching towards relief: The Kent-Collins protocol for radiation-induced eustachian tube dysfunction

Abstract Background: Eustachian tube dysfunction is a common side effect of radiotherapy for head and neck cancers or brain tumors, although few effective treatments exist. The Kent-Collins Protocol represents a novel therapeutic option for post-radiotherapy Eustachian tube dysfunction. Case Presentation: The Kent-Collins Protocol was employed in one patient with Eustachian tube dysfunction following fractionated stereotactic radiotherapy for HER-2 positive breast cancer with cerebral metastases. The Kent-Collins Protocol provided relief of symptoms (conductive hearing loss, aural fullness, and otalgia) for a range of 5 to 45 minutes. The protocol could be repeated when symptoms returned to provide additional relief. The patient also reported psychological benefit from this protocol, knowing the hearing loss was reversible and not likely to be permanent. Conclusions: This case demonstrates the potential of The Kent-Collins Protocol for the treatment of post-radiotherapy Eustachian tube dysfunction. The protocol is effective, inexpensive, easy to teach, and safe, offering an alternative to invasive therapies currently in existence. Citation Format: Matthew E Kent, Patrick J Colllins, Ayal A Aizer. Stretching towards relief: The Kent-Collins protocol for radiation-induced eustachian tube dysfunction [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A082.

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.

Setup margins based on the inter- and intrafractional setup error of left-sided breast cancer radiotherapy using deep inspiration breath-hold technique (DIBH) and surface guided radiotherapy (SGRT).

The use of volumetric modulated arc therapy (VMAT), simultaneous integrated boost (SIB), and hypofractionated regimen requires adequate patient setup accuracy to achieve an optimal outcome. The purpose of this study was to assess the setup accuracy of patients receiving left-sided breast cancer radiotherapy using deep inspiration breath-hold technique (DIBH) and surface guided radiotherapy (SGRT) and to calculate the corresponding setup margins. The patient setup accuracy between and within radiotherapy fractions was measured by comparing the 6DOF shifts made by the SGRT system AlignRT with the shifts made by kV-CBCT. Three hundred and three radiotherapy fractions of 23 left-sided breast cancer patients using DIBH and SGRT were used for the analysis. All patients received pre-treatment DIBH training and visual feedback during DIBH. An analysis of variance (ANOVA) was used to test patient setup differences for statistical significance. The corresponding setup margins were calculated using the van Herk's formula. The intrafractional patient setup accuracy was significantly better than the interfractional setup accuracy (p<0.001). The setup margin for the combined inter- and intrafractional setup error was 4, 6, and 4mm in the lateral, longitudinal, and vertical directions if based on SGRT alone. The intrafractional error contributed ≤1mm to the calculated setup margins. With SGRT, excellent intrafractional and acceptable interfractional patient setup accuracy can be achieved for the radiotherapy of left-sided breast cancer using DIBH and modern radiation techniques. This allows for reducing the frequency of kV-CBCTs, thereby saving treatment time and radiation exposure.