Karen Long

Evaluation of target and cardiac position during visually monitored deep inspiration breath-hold for breast radiotherapy

A low-resource visually monitored deep inspiration breath-hold (VM-DIBH) technique was successfully implemented in our clinic to reduce cardiac dose in left-sided breast radiotherapy. In this study, we retrospectively characterized the chest wall and heart positioning accuracy of VM-DIBH using cine portal images from 42 patients. Central chest wall position from field edge and in-field maximum heart distance (MHD) were manually measured on cine images and compared to the planned positions based on the digitally reconstructed radiographs (DRRs). An in-house program was designed to measure left anterior descending artery (LAD) and chest wall separation on the planning DIBH CT scan with respect to breath-hold level (BHL) during simulation to determine a minimum BHL for VM-DIBH eligibility. Systematic and random setup uncertainties of 3.0 mm and 2.6 mm, respectively, were found for VM-DIBH treatment from the chest wall measurements. Intrabeam breath-hold stability was found to be good, with over 96% of delivered fields within 3 mm. Average treatment MHD was significantly larger for those patients where some of the heart was planned in the field compared to patients whose heart was completely shielded in the plan (p < 0.001). No evidence for a minimum BHL was found, suggesting that all patients who can tolerate DIBH may yield a benefit from it. PACS number(s): 87.53.Jw, 87.53.Kn, 87.55.D.A low‐resource visually monitored deep inspiration breath‐hold (VM‐DIBH) technique was successfully implemented in our clinic to reduce cardiac dose in left‐sided breast radiotherapy. In this study, we retrospectively characterized the chest wall and heart positioning accuracy of VM‐DIBH using cine portal images from 42 patients. Central chest wall position from field edge and in‐field maximum heart distance (MHD) were manually measured on cine images and compared to the planned positions based on the digitally reconstructed radiographs (DRRs). An in‐house program was designed to measure left anterior descending artery (LAD) and chest wall separation on the planning DIBH CT scan with respect to breath‐hold level (BHL) during simulation to determine a minimum BHL for VM‐DIBH eligibility. Systematic and random setup uncertainties of 3.0 mm and 2.6 mm, respectively, were found for VM‐DIBH treatment from the chest wall measurements. Intrabeam breath‐hold stability was found to be good, with over 96% of delivered fields within 3 mm. Average treatment MHD was significantly larger for those patients where some of the heart was planned in the field compared to patients whose heart was completely shielded in the plan (p < 0.001). No evidence for a minimum BHL was found, suggesting that all patients who can tolerate DIBH may yield a benefit from it. PACS number(s): 87.53.Jw, 87.53.Kn, 87.55.D‐

Dosimetric variations in permanent breast seed implant due to patient arm position.

PURPOSE Planning and delivery for permanent breast seed implant (PBSI) are performed with the ipsilateral arm raised; however, changes in implant geometry can be expected because of healing and anatomical motion as the patient resumes her daily activities. The purpose of this study is to quantify the effect of ipsilateral arm position on postplan dosimetry. METHODS AND MATERIALS Twelve patients treated at the Tom Baker Cancer Centre were included in this study. Patients underwent two postimplant CT scans on the day of implant (Day 0) and two scans approximately 8 weeks later (Day 60). One scan at each time was taken with the ipsilateral arm raised, recreating the planning scan position, and the other with both arms down in a relaxed position beside the body, recreating a more realistic postimplant arm position. Postplans were completed on all four scans using deformable image registration (MIM Maestro). RESULTS On the Day 0 scan, the V200 for the evaluation planning target volume was significantly increased in the arm-down position compared with the arm-up position. Lung, rib, and chest wall dose were significantly reduced at both time points. Left anterior descending coronary artery, heart, and skin dose showed no significant differences at either time point. CONCLUSIONS Although some dosimetric indices show significant differences between the arm-up and arm-down positions, the magnitude of these differences is small and the values remain indicative of implant quality. Despite the delivery of the majority of dose with the arm down, it is reasonable to use CT scans taken in the arm-up position for postplanning.

Including internal mammary lymph nodes in radiation therapy for synchronous bilateral breast cancer: an international survey of treatment technique and clinical priorities

PurposeThe aim of this study was to understand the international standard practice for radiation therapy treatment techniques and clinical priorities for institutions including the internal mammary lymph nodes (IMLNs) in the target volume for patients with synchronous bilateral breast cancer.MethodsAn international survey was developed to include questions that would provide awareness of favored treatment techniques, treatment planning and delivery resource requirements, and the clinical priorities that may lead to the utilization of preferred treatment techniques.ResultsOf the 135 respondents, 82 indicated that IMLNs are regularly included in the target volume for radiation therapy (IMLN-inclusion) when the patient is otherwise generally indicated for regional nodal irradiation. Of the 82 respondents that regularly include IMLNs, five were removed as those respondents do not treat this population synchronously. Of the 77 respondents, institutional standard of care varied significantly, though VMAT (34%) and combined static photon and electron fields (21%) were the most commonly utilized techniques. Respondents did preferentially select target volume coverage (70%) as the most important clinical priority, followed by normal tissue sparing (25%).ConclusionThe results of the survey indicate that the IMLN-inclusion for radiation therapy has not yet been comprehensively adopted. As well, no consensus on best practice for radiation therapy treatment techniques has been reached.

114: Patient Positioning and Mark-Up Optimization for Permanent Breast Seed Implant (PBSI)

S43 _________________________________________________________________________________________________________ in Ontario (ONT) and to develop recommendations to ensure all patients to have equitable access to MR-guided brachytherapy (MRgBT) for cervical cancer. Methods: A qualitative phone interview was designed by the GYN CoP working group to survey the current state of ccBT in the province. Questions were developed to inquire about the current use of image-guided ccBT and the associated referral processes, the usage of MR imaging in ccBT and the current use of imageguided interstitial GYN BT. All ONT cancer centres offering radiation treatments to GYN cancers were included. Two group members conducted and audio recorded the telephone interviews from May to November 2015 and analyzed all recordings and summarized the data. Results: Thirteen (n = 13) ONT cancer centres were interviewed. Of these, three centres do not offer ccBT, five centres offer CTguided ccBT, four centres offer a combination of CT-MR-guided ccBT and one centre offers strictly MR-guided ccBT. The three centres that do not offer ccBT have established referral processes with three tertiary cancer centres in ONT respectively. However, there is no standardized referral process, referral timing, or method of communication. Other practices vary throughout the centres. Three of 13 centres suggested developing a file portal to standardize and facilitate the sharing of external beam and BT plans, distributions and images. All CTguided ccBT centres except one have plans to develop MRgBT. The tertiary centres mentioned above are also the only centres that offer interstitial GYN BT. They are located in the southwestern part of the province. Of these, one centre offers CT-guided and two centres offer MR-guided interstitial GYN BT. There is currently no standardized guideline to identify patient candidates for interstitial GYN BT. Conclusions: This study demonstrated that models of shared care exist and are functioning in ONT. While referral processes are functioning well, some areas represent opportunities for improvement. Future work is needed by the GYN CoP to improve referral processes and to develop consensus on indications for interstitial brachytherapy. This will ensure all patients in ONT have access to this high quality brachytherapy.