Repeatability and reproducibility of prostate apparent diffusion coefficient values on a 1.5 T magnetic resonance linear accelerator.

Background and Purpose: Integrated magnetic resonance linear accelerator (MR-Linac) systems offer potential for biologically based adaptive radiation therapy using apparent diffusion coefficient (ADC). Accurate tracking of longitudinal ADC changes is key to establishing ADC-driven dose adaptation. Here, we report repeatability and reproducibility of intraprostatic ADC using deformable image registration (DIR) to correct for inter-fraction prostate changes. Materials and Methods: The study included within-fraction repeat ADC measurements for three consecutive fractions for 20 patients with prostate cancer treated on a 1.5 T MR-Linac. We deformably registered successive fraction T2-weighted images and applied the deformation vector field to corresponding ADC maps to align to fraction 2. We delineated gross tumour volume (GTV), peripheral zone (PZ) and prostate clinical target volume (CTV) regions-of-interest (ROIs) on T2-weighted MRI and copied to ADC maps. We computed intraclass correlation coefficients (ICC) and percent repeatability coefficient (%RC) to determine within-fraction repeatability and between-fraction reproducibility for individual voxels, mean and 10th percentile ADC values per ROI. Results: The ICC between repeats and fractions was excellent for mean and 10th percentile ADC in all ROIs (ICC > 0.86), and moderate repeatability and reproducibility existed for individual voxels (ICC > 0.542). Similarly, low %RC within-fraction (4.2-17.9 %) mean and 10th percentile ADC existed, with greater %RC between fractions (10.2-36.8 %). Higher %RC existed for individual voxel within-fraction (21.7-30.6 %) and between-fraction (32.1-34.5 %) ADC. Conclusions: Results suggest excellent ADC repeatability and reproducibility in clinically relevant ROIs using DIR to correct between-fraction anatomical changes. We established the precision of voxel-level ADC tracking for future biologically based adaptation implementation.

Prospective evaluation of patient-reported anxiety and experiences with adaptive radiation therapy on an MR-linac.

Purpose: An integrated magnetic resonance scanner and linear accelerator (MR-linac) was implemented with daily online adaptive radiation therapy (ART). This study evaluated patient-reported experiences with their overall hospital care as well as treatment in the MR-linac environment. Methods: Patients pre-screened for MR eligibility and claustrophobia were referred to simulation on a 1.5 T MR-linac. Patient-reported experience measures were captured using two validated surveys. The 15-item MR-anxiety questionnaire (MR-AQ) was administered immediately after the first treatment to rate MR-related anxiety and relaxation. The 40-item satisfaction with cancer care questionnaire rating doctors, radiation therapists, the services and care organization and their outpatient experience was administered immediately after the last treatment using five-point Likert responses. Results were analyzed using descriptive statistics. Results: 205 patients were included in this analysis. Multiple sites were treated across the pelvis and abdomen with a median treatment time per fraction of 46 and 66 min respectively. Patients rated MR-related anxiety as "not at all" (87%), "somewhat" (11%), "moderately" (1%) and "very much so" (1%). Positive satisfaction responses ranged from 78 to 100% (median 93%) across all items. All radiation therapist-specific items were rated positively as 96-100%. The five lowest rated items (range 78-85%) were related to general provision of information, coordination, and communication. Overall hospital care was rated positively at 99%. Conclusion: In this large, single-institution prospective cohort, all patients had low MR-related anxiety and completed treatment as planned despite lengthy ART treatments with the MR-linac. Patients overall were highly satisfied with their cancer care involving ART using an MR-linac.

Impact of technological advances in treatment planning, image guidance, and treatment delivery on target margin design for prostate cancer radiotherapy: an updated review.

Recent innovations in image guidance, treatment delivery, and adaptive radiotherapy (RT) have created a new paradigm for planning target volume (PTV) margin design for patients with prostate cancer. We performed a review of the recent literature on PTV margin selection and design for intact prostate RT, excluding post-operative RT, brachytherapy, and proton therapy. Our review describes the increased focus on prostate and seminal vesicles as heterogenous deforming structures with further emergence of intra-prostatic GTV boost and concurrent pelvic lymph node treatment. To capture recent innovations, we highlight the evolution in cone beam CT guidance, and increasing use of MRI for improved target delineation and image registration and supporting online adaptive RT. Moreover, we summarize new and evolving image-guidance treatment platforms as well as recent reports of novel immobilization strategies and motion tracking. Our report also captures recent implementations of artificial intelligence to support image guidance and adaptive RT. To characterize the clinical impact of PTV margin changes via model-based risk estimates and clinical trials, we highlight recent high impact reports. Our report focusses on topics in the context of PTV margins but also showcase studies attempting to move beyond the PTV margin recipes with robust optimization and probabilistic planning approaches. Although guidelines exist for target margins conventional using CT-based image guidance, further validation is required to understand the optimal margins for online adaptation either alone or combined with real-time motion compensation to minimize systematic and random uncertainties in the treatment of patients with prostate cancer.

Practice-based training strategy for therapist-driven prostate MR-Linac adaptive radiotherapy.

Purpose: To develop a practice-based training strategy to transition from radiation oncologist to therapist-driven prostate MR-Linac adaptive radiotherapy. Methods and materials: In phase 1, 7 therapists independently contoured the prostate and organs-at-risk on T2-weighted MR images from 11 previously treated MR-Linac prostate patients. Contours were evaluated quantitatively (i.e. Dice similarity coefficient [DSC] calculated against oncologist generated online contours) and qualitatively (i.e. oncologist using a 5-point Likert scale; a score ≥ 4 was deemed a pass, a 90% pass rate was required to proceed to the next phase). Phase 2 consisted of supervised online workflow with therapists required no intervention from the oncologist on 10 total cases to advance. Phase 3 involved unsupervised therapist-driven workflow, with offline support from oncologists prior to the next fraction. Results: In phase 1, the mean DSC was 0.92 (range 0.85-0.97), and mean Likert score was 3.7 for the prostate. Five therapists did not attain a pass rate (3-5 cases with prostate contour score < 4), underwent follow-up one-on-one review, and performed contours on a further training set (n = 5). Each participant completed a median of 12 (range 10-13) cases in phase 2; of 82 cases, minor direction were required from the oncologist on 5 regarding target contouring. Radiation oncologists reviewed 179 treatment fractions in phase 3, and deemed 5 cases acceptable but with suggestions for next fraction; all other cases were accepted without suggestions. Conclusion: A training stepwise program was developed and successfully implemented to enable a therapist-driven workflow for online prostate MR-Linac adaptive radiotherapy.

Assessment of intra-fraction motion during frameless image guided Gamma Knife stereotactic radiosurgery.

As frameless stereotactic radiosurgery increase in use, the aim of this study was to evaluate intra-fraction motion through cone-beam CT (CBCT) and high-definition motion management (HDMM) systems. Intra-fraction motion measured between localization, repeat localization and post-treatment CBCTs were correlated to intra-faction motion indicated by the HDMM files using the Pearson coefficient (r). A total of 302 plans were reviewed from 263 patients (114 male, 149 female); 216 pairs of localization-repeat localization, and 260 localization-post-treatment CBCTs were analyzed against HDMM logs. We found the magnitude of intra-fraction motion detected by the HDMM system were larger than the corresponding CBCT results.

Impact of intrafraction changes in delivered dose of the day for prostate cancer patients treated with stereotactic body radiotherapy via MR-Linac.

Purpose: The purpose of this study is to evaluate the impact of intrafraction pelvic motion by comparing the adapted plan dose (APD) and the computed delivered dose of the day (DDOTD) for patients with prostate cancer (PCa) treated with SBRT on the MR-Linac. Methods: Twenty patients with PCa treated with MR-guided adaptive SBRT were included. A 9-field IMRT distribution was adapted based on the anatomy of the day to deliver a total prescription dose of 3000 cGy in 5 fractions to the prostate plus a 5 mm isotropic margin. Prostate, bladder, and rectum were re-contoured on the MR-image acquired during treatment delivery (MRBO). DDOTD was computed by propagating the dose from the daily adapted plan generated during treatment onto the MRBO. Results: Target coverage was met for all fractions, however, computed DDOTD was significantly less than the APD (p < 0.05). During an average treatment of 53 min, mean bladder volume increased by 116%, which led to a significant decrease in the DDOTD bladder D40% (p < 0.001). However, DDOTD to bladder 5 cc was significantly higher (p < 0.001) than APD. Rectum intrafraction changes were observed based on a volume change of -20% to 83% and presence of significant dose changes from APD to DDOTD for rectum D20% (p < 0.05) and D1cc (p < 0.0001). Conclusions: Intrafraction motion observed during prostate SBRT treatment on the MR-Linac have dosimetric impacts on both the target and organs at risk. Post-treatment computation using DDOTD may inform adaptation beyond anatomic changes in subsequent treatment fractions to best capitalize on MR-Linac technology and widen the therapeutic index of SBRT for PCa.

Case Report: MR-Guided Adaptive Radiotherapy, Some Room to Maneuver.

Background: A magnetic resonance linear accelerator (MR-Linac) provides superior soft tissue contrast to evaluate inter- and intra-fraction motion and facilitate online adaptive radiation therapy (ART). We present here an unusual case of locally advanced castrate-resistant prostate cancer treated with high-dose palliative ultra-hypofractionated radiation therapy on the MR-Linac with significant inter-fraction tumor regression. Case Presentation: The patient was a 65-year-old man diagnosed with metastatic prostate cancer to bone and pelvic lymph nodes 7 years prior. At diagnosis, he presented with a PSA of 23 ng/ml and was commenced on a luteinizing hormone-releasing hormone agonist, achieving a PSA nadir of 4.68 ng/ml at 12 months. The patient subsequently had progressive lower urinary tract symptoms, his PSA increased to 47 ng/ml, and there was a markedly enlarged pelvic mass involving the prostate with gross extra-capsular disease and invasion into the posterior bladder wall. The patient was referred for palliative radiation to the pelvic mass due to urinary symptoms, pain, and lower limb paraesthesia. Treatment was planned to be delivered on the MR-Linac with a schedule of 36 Gy over 6 weekly factions allowing for maximal target dose delivery while minimizing surrounding organs at risk (OARs) radiation exposure. Unexpectedly, the target volume had a marked 49% (453 cc to 233 cc) reduction that was accounted for in the online adaptive process. A new reference plan was generated after 3 fractions to add sacral plexus as an OAR, previously not visible due to mass encroachment. The patient reported ongoing reduction in urinary symptoms, pelvic pain, and lower limb paresthesia by the end of treatment. Conclusion: Using daily MR-guided ART, improved visualization of the changing target and OARs ensured safe dose escalation. The unexpected positive response of the target and improved patient outcomes demonstrated the added value of the MR-Linac for online adaptive radiotherapy in this setting.

Dosimetric comparison of MR-guided adaptive IMRT versus 3DOF-VMAT for prostate stereotactic radiotherapy.

INTRODUCTION: To compare the dosimetry of prostate stereotactic radiotherapy (SBRT) delivered by adaptive intensity modulated radiotherapy (A-IMRT) and 3 degree of freedom volumetric modulated arc therapy (3DOF-VMAT). METHODS & MATERIALS: Twenty-five prostate patients treated with High Dose Rate (HDR) brachytherapy followed by SBRT were included (fifteen with hydrogel spacer in place for treatment). Interfraction changes in the volume of prostate, rectum and bladder were measured. Fractional dose to these structures was estimated for A-IMRT and 3DOF-VMAT for comparison against the corresponding reference dose and between each other. RESULTS: Clinically acceptable dose was delivered to prostate in all 125 fractions through A-IMRT and 3DOF-VMAT. A-IMRT was better than 3DOF-VMAT in reducing dose to 1 cm3 of rectum. Conversely, 3DOF-VMAT was superior in sparing 50% and 20% of rectum. When comparing the reference and delivered dose, there was no significant difference for Bladder D5cm3 for either technique. However, rectum in the high dose region benefited more from A-IMRT by being irradiated to a lower than reference dose in more fractions than 3DOF-VMAT. Hydrogel spacer reduced the rectal dose and was associated with a smaller deviation from reference dose for rectum D50% for A-IMRT. CONCLUSIONS: Despite the presence of large interfraction organ volumes changes, clinically acceptable dose was delivered to the prostate by both systems. A-IMRT facilitated a greater rectal sparing from the high dose region than 3DOF-VMAT. Further reduction in rectal dose could be achieved by hydrogel spacer to displace the rectum, or by adaptation delivered by VMAT.

MRI-Guided Online Adaptive Stereotactic Body Radiation Therapy of Liver and Pancreas Tumors on an MR-Linac System.

PURPOSE: To describe a comprehensive workflow for MRI-guided online adaptive stereotactic body radiation therapy (SBRT) specific to upper gastrointestinal cancer patients with abdominal compression on a 1.5T MR-Linac system. Additionally, we discuss the workflow's clinical feasibility and early experience in the case of 16 liver and pancreas patients. METHODS: Eleven patients with liver cancer and five patients with pancreas cancer were treated with online adaptive MRI-guidance under abdominal compression. Two liver patients received single-fraction treatments; the remainder plus all pancreas cancer patients received five fractions. A total of 65 treatment sessions were investigated to provide analytics relevant to the online adaptive processes. The quantification of target and organ motion as well as definition and validation of internal target volume (ITV) margins were performed via multi-contrast imaging provided by three different 2D cine sequences. The plan generation was driven by full re-optimization strategies and using T2-weighted 3D image series acquired by means of a respiratory-triggered exhale phase or a time-averaged imaging protocol. As a pre-requisite for the clinical development of the procedure, the image quality was thoroughly investigated via phantom measurements and numerical simulations specific to upper abdominal sites. The delivery of the online adaptive treatments was facilitated by real-time monitoring with 2D cine imaging. RESULTS: Liver 1-fraction and 5-fraction online adaptive session time were on average 80 and 67.5 min, respectively. The total session length varied between 70-90 min for a single fraction and 55-90 min for five fractions. The pancreas sessions were 54-85 min long with an average session time of 68.2 min. Target visualization on the 2D cine image data varied per patient, with at least one of the 2D cine sequences providing sufficient contrast to confidently identify its location and confirm reproducibility of ITV margins. The mean/range of absolute and relative dose values for all treatment sessions evaluated with ArcCheck were 90.6/80.9-96.1% and 99/95.4-100%, respectively. CONCLUSION: MR-guidance is feasible for liver and pancreas tumors when abdominal compression is used to reduce organ motion, improve imaging quality, and achieve a robust intra- and inter-fraction patient setup. However, the treatment length is significantly longer than for the conventional linac, and patient compliance is paramount for the successful completion of the treatment. Opportunities for reducing the online adaptive session time should be explored. As the next steps, dose-of-the-day and dose accumulation analysis and tools are needed to enhance the workflow and to help further refine the online re-planning processes.

Could knowledge of patient demographics facilitate a personalized approach to radiation therapy patient education?

INTRODUCTION: Using patient demographics to tailor cancer patient education processes results in improved patient outcomes. However, there is little information on how to successfully tailor radiation therapy (RT) educational content and delivery. The aim of this quality improvement project was to describe the information preferences of a diverse group of patients undergoing RT and determine if different RT education processes were associated with certain patient demographics. MATERIALS AND METHODS: An educational needs assessment questionnaire, based on a validated tool, was offered to all patients undergoing RT on a single day. Questionnaire sections included demographics and questions regarding the importance of topics related to RT treatments, desired mode of information delivery, quantity of information, desired timing of information, and satisfaction with information received. Patients were also asked to answer qualitative questions focused on what was working well and what could be improved. Participants' responses were cohorted based on demographic groupings (age, gender, education level) and were tested for statistically significant differences and associations. RESULTS: 130 patients completed the questionnaire. Compared to those over 60 years, more participants who were 50 - 59 years old thought the topics were 'very important' (96% vs 77%, p<0.001) and wanted a higher quantity of information about the topics (80% vs 66%, p<0.001). More participants over 70 years old preferred pamphlets compared to those less than 70 years (48% vs 30%, p<0.047) while more participants under 50 years old preferred one-on-one sessions compared to those older than 50 years (40% vs 25%, p<0.038). Fewer participants <50 years wanted information at their first meeting with the Radiation Oncologist compared to those older than 50 years (57% vs 73%, p<0.001). Compared to the male cohort, more female participants felt the information topics were more important (83% vs 74%, p<0.0001) and had more unmet education needs (29% vs 17%, p<0.001). Compared to those with post-secondary education, more participants with primary or high school education desired a higher quantity of information (76% vs 65%, p<0.001), preferred to receive that information using pamphlets (43% vs 32%, p=0.006) and wanted all the information at the first opportunity (81% vs 67%, p<0.001). CONCLUSIONS: This quality improvement project found that age, gender and education level influenced patient preferences for information quantity, delivery mode and timing of RT education. These findings are promising and support further evaluations to determine a more precise definition of the personal factors that could help to individualize our approach to educating patients receiving RT.

Facilitators and barriers to getting obstructive sleep apnea diagnosed: perspectives from patients and their partners.

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is a prevalent and debilitating condition that is significantly underdiagnosed. The majority of adults sleep with someone-a partner. Partners can play a significant role in the patient's OSA diagnosis. The goal of this work is to describe facilitators and barriers to OSA diagnosis as discussed by patients with OSA and their partners. METHODS: This was a qualitative secondary analysis with results drawn from 20 dyadic interviews, conducted 1 couple at a time, in 20 newly diagnosed adult patients with OSA and their partners. Qualitative interview data were analyzed using conventional content analysis. RESULTS: Facilitators of OSA diagnosis were partners pushing patients to seek care, patients actively seeking care, and care providers identifying the patient's risk of OSA. Barriers to OSA diagnosis were patients' lack of serious attention to symptoms, patients' negative perceptual framing of diagnosis and treatment of OSA, and poor coordination of health care services. CONCLUSIONS: We recommend engaging partners in the OSA diagnosis and developing educational and behavioral interventions to raise public awareness about OSA. It is important to educate clinicians on atypical presentations of OSA. Further investigation is needed to evaluate the impact of health care services on OSA diagnosis. CITATION: Ye L, Li W, Willis DG. Facilitators and barriers to getting obstructive sleep apnea diagnosed: perspectives from patients and their partners. J Clin Sleep Med. 2022;18(3):835-841.

Patient perspectives on frame versus mask immobilization for gamma knife stereotactic radiosurgery.

PURPOSE: To assess patient experiences and perspectives following Gamma Knife (GK) stereotactic radiosurgery (SRS) using frame versus mask immobilization. METHODS: Patients who received GK-SRS using both frame and mask immobilization were included in this study. One-on-one semi-structured interviews, led by a third-party expert, were used to gain insight into the patient experience. To reduce memory bias of either immobilization device, patients underwent the interview at their follow-up appointment. Initial assessment of patient transcriptions was completed by one study staff; a second member reviewed transcripts for thematic saturation. All interviews were independently coded for themes to minimize interpretation bias. RESULTS: Fifteen patients were consented; 12 were successfully interviewed (3 lost due to deteriorating health status). Interviews ranged from 30 to 60 min in duration. The most common patient concern regarding the frame was pain (9 patients), while the primary concerns with the mask system were the ability to remain still (6 patients) and claustrophobia (4 patients). Eleven patients chose the mask as their preferred choice in terms of their overall experience. Two themes emerged during the interviews that spoke to patient satisfaction with each process: unexpected pain with frame placement; and tightness experienced while wearing the mask during treatment. CONCLUSIONS: From the patient perspective there was overwhelming agreement that the mask was the preferred choice for GK-SRS. The patient experience could be improved by enhanced education to better prepare patients on what to expect during the frame placement and mask treatment processes.

A Multidisciplinary Approach to Implement Image-Guided Craniospinal Irradiation.

PURPOSE: Practical considerations dictated a change in the craniospinal irradiation (CSI) technique. We report our experience in developing and refining CSI planning and treatment parameters, using a 3-isocenter image-guided intensity-modulated radiation therapy (IG-IMRT) technique. METHODS AND MATERIALS: Two institutional values guided development: multidisciplinary decision-making and coordinated considerations throughout simulation, planning, and delivery. Patient immobilization and simulation parameters were selected based on treatment delivery system limitations. Commissioning fluence verification maps were acquired to verify dose in regions of overlapping fields. Robustness analysis was performed to assess impact of potential setup errors measured through IGRT verification. Treatment considerations included order of isocenter imaging and treatment and respective IGRT frequency, modality, and image registration thresholds. RESULTS: Overall film measurements were within 3% of planned dose, confirmed by phantom composite measurements showing all points were within 97% of planned dose. Setup sensitivity analysis suggested a 3-mm setup tolerance was sufficient to ensure confidence in the delivered plan. As the most critical organs at risk were in the superior isocenter, the daily isocenter treatment order was confirmed as superior, middle, and inferior. Daily cone beam computed tomography guidance was chosen for all isocenters (3° rotational threshold). Except for the superior/inferior direction of the middle and inferior isocenters, which were adjusted to 3 mm based on sensitivity analysis, a 1-mm translational threshold was used. CONCLUSIONS: An IG-IMRT CSI technique has been developed and implemented in our institution through a multidisciplinary approach. This process highlights the collaborative, iterative approach used to successfully integrate a new treatment technique in an image-guidance era.

Impact of Immobilization on Interfractional Errors for Upper Extremity Soft Tissue Sarcoma Radiation Therapy.

INTRODUCTION/BACKGROUND: Owing to the rare nature and presentation of upper extremity soft tissue sarcomas (STSs) and the high mobility of associated anatomy, various patient positioning strategies are used for radiation therapy. The purpose of this study is to measure the interfractional setup errors associated with upper extremity sarcomas using different immobilization methods through cone-beam computed tomography (CBCT) images. METHODS: All patients treated with daily CBCT guidance for upper extremity STSs during 2014-2015 were identified and triaged based on type of immobilization. After defining an optimal region of interest for image registration, daily CBCT images were automatically registered to reference CT images to quantify positional discrepancies. Means and standard deviations were calculated, and one-way analysis of variance was calculated to determine significance of data. RESULTS: Seventeen patients with upper extremity sarcoma met inclusion criteria: 13 were treated to the shoulder/axilla/upper arm and 4 to the arm/elbow/forearm. Three main types of immobilization were identified: vacuum cradle with custom thermoplastic shell, vacuum cradle alone, and no immobilization accessory used. Patient repositioning occurred if translational and rotational displacements were larger than 1 mm and 5°, respectively, as per institutional guidelines. Patient repositioning rates were 18% for vacuum cradle with thermoplastic shells, 15% for vacuum cradles only, and 6% for no immobilization accessories. Mean translational displacements in right/left (R/L), superior/inferior (S/I), and anterior/posterior (A/P) directions were -0.04 ± 0.33 cm, 0.32 ± 0.33 cm, and 0.12 ± 0.25 cm for vacuum cradle with thermoplastic shell; 0.25 ± 0.10 cm, -0.07 ± 0.22 cm, and 0.00 ± 0.17 cm for vacuum cradle alone; and 0.14 ± 0.15 cm, 0.08 ± 0.45 cm, and -0.01 ± 0.24 cm for no immobilization. For all patients, rotational displacements in the pitch, roll, and yaw were 0.15 ± 1.99°, 0.31 ± 2.11°, and -0.21 ± 1.76°, respectively. There were significant (P < .05) differences in systematic error values for all translational and rotational axes between immobilization methods. CONCLUSION: Large interfractional errors, especially in the rotational axes, were observed, regardless of immobilization strategy. Small study population and unequal representation of different parts of the upper extremity are identified limitations. The need for better immobilization techniques for upper extremity STS treatments is clearly demonstrated.

The Effect of Lumpectomy Cavity Changes on Planning Dose in Breast Radiotherapy Boost.

INTRODUCTION: The addition of a postoperative tumour bed (cavity) boost after whole-breast radiotherapy (RT) is known to decrease the risk of local in-breast recurrence. The purpose of this retrospective study is to assess breast excision cavity changes and planned doses at the time of initial boost RT treatments after the completion of whole-breast RT. METHODS: Over a 4-month period, women with highly visible cavity on computed tomography (CT) and treated with whole-breast RT followed by a conformal photon boost to the tumour bed were identified. The patient's day 1 boost online cone beam CT (CBCT) and corresponding setup corrections were overlaid with the planning CT image. The cavity and dose evaluation volumes (DEVs = 1 cm expansion of the cavity, excluding 5 mm of lung and skin) were assessed. Dosimetric evaluations were performed for maximum and minimum cavity doses, cavity volume receiving 90% (V90) and 95% (V95) of prescription dose, and DEV receiving 85% (V85), 95%, and 105% (V105) of the prescription dose. The two-tailed student t-test and Pearson's correlation test were performed for statistical analysis. RESULTS: Eighteen patients were included in the analysis. The CT cavity (CAVCT) volume (mean: 28.8 cc, SD 27.9) was larger than the CBCT cavity (CAVCBCT) volume (mean: 21.1 cc, SD: 22.4) (P value= .003). The CT DEV similarly decreased at the time of boost; DEVCT (mean: 113.9 cc, SD: 63.2) versus DEVCBCT (mean: 92.3 cc, SD: 50.8), (P = .002). A strong correlation was observed between the initial CT cavity volume and cavity shrinkage observed at time of boost (day 1 CBCT) (Pearson's r = 0.697; r2= 0.486, P = .001). Both time periods from surgery to CT (median: 92 days, range: 31-227) and from surgery to day 1 CBCT (median: 141 days, range: 56-265) were not associated with cavity volume change. However, an inverse correlation was observed between time from initial CT to day 1 boost CBCT (median: 33 days, range: 24-54) and % cavity volume change (Pearson's r = -0.642; r2= 0.4121, P = .004). Dosimetric evaluations of the cavity and DEV showed no significant differences in maximum, minimum, and target dose coverage between the CT and boost volumes. CONCLUSION: In patients with breast cancer treated with a tumour bed boost after whole-breast RT, the postoperative cavity can shrink between the time of CT and day 1 boost. The extent of cavity reduction was greatest in patients with large postoperative cavities on initial CT. Despite the cavity size change, conformal boost fields provide adequate dose coverage to the cavity.

Impact of a pharmacy-led smoking cessation clinic in a dermatology centre.

INTRODUCTION: Cigarette smoking is a leading cause of morbidity and mortality, and has a deleterious effect on dermatological conditions, such as skin cancers, hidradenitis suppurativa and psoriasis. The study aimed to evaluate the efficacy of a pharmacist-led smoking cessation clinic in reducing cigarette smoking at a tertiary referral dermatology centre. We described the impact of this clinic to provide guidance on how such a model could be further improved and implemented more widely. METHODS: In this single-centre, retrospective study, 74 currently smoking patients who received counselling at a structured smoking cessation clinic between January 2010 and March 2013 were identified. Information on baseline demographic characteristics and detailed past medical history, including smoking history, was collected. Follow-up was conducted at two weeks and three months. RESULTS: At the first follow-up at two weeks, which was attended by 57 patients, 9 (15.8%) had stopped smoking and 26 (45.6%) showed reduction in the number of cigarette sticks smoked per day, with an average reduction of 4.1 cigarette sticks per day. However, a few patients also reported no change or increased number of cigarette sticks smoked per day following counselling. CONCLUSION: A structured pharmacist-led smoking cessation clinic is effective and can be made a part of the holistic management of dermatological conditions.

Patterns of practice of adaptive re-planning for anatomic variances during cone-beam CT guided radiotherapy.

PURPOSE: Substantial, unanticipated anatomic variances during cone-beam CT (CBCT)-guided radiotherapy can potentially impact treatment accuracy and clinical outcomes. This study assessed patterns of practice of CBCT variances reported by RTTs and subsequent interventions for multiple-disease sites. METHODS: A chart review was conducted at a large cancer centre for patients treated with daily online CBCT-guided radiotherapy. Patients selected for review were identified via RTT-reported variances that then triggered offline multi-disciplinary assessment. Cases were categorized by the type of anatomic variance observed on CBCT and any further interventions recorded such as un-scheduled adaptive re-planning. RESULTS: Over a 1-year period, 287 variances from 261 patients were identified (6.2% of the 4207 patients treated with daily CBCT-guided radiotherapy), most often occurring within the first 5 fractions of the treatment course. Of these variances, 21% (59/287) were re-planned and 3.5% (10/287) discontinued treatment altogether. Lung was the most frequent disease-site (27% of 287 variances) reported with IGRT-related variances although head and neck and sarcoma were most frequently re-planned (19% of 59 re-plans for each site). Technical or clinical rationales for re-planning were not routinely documented in patient medical records. All disease-sites had numerous categories of variances. Three of the four most frequent categories were for tumor-related changes on CBCT, and the re-planning rate was highest for tumor progression at 25%. Normal tissue variances were the second most frequency category, and re-planned in 14% of those cases. CONCLUSION: RTTs identified a wide range of anatomic variances during CBCT-guided radiotherapy. In a minority of cases, these substantially altered the care plan including ad hoc adaptive re-planning or treatment discontinuation. Improved understanding of the clinical decisions in these cases would aid in developing more routine, systematic adaptive strategies.

Evidence-based region of interest matching guidelines for sarcoma volumetric image-guided radiation therapy.

PURPOSE: Region-of-interest (ROI) guidelines for online cone-beam computed tomography (CBCT) radiotherapy may improve matching reproducibility and reduce inter-user variability of soft tissue sarcoma (STS) image guidance. The purpose of this work is to standardize ROI STS CBCT image registration guidelines using the plan-do-study-act (PDSA) cycle for the lower extremity, retroperitoneal, pelvis, and thorax. METHODS: Based on anatomic bony surrogates, initial ROI matching guidelines for STS were developed by a team of radiation therapists, physicists and oncologists (Plan). Retrospective, qualitative evaluation of the guidelines was completed by the designated sarcoma lead therapist to determine clinical feasibility (Do). Validation of the ROI guidelines was performed through independent evaluation by radiation therapy CBCT imaging experts on a cohort of 10 patients per anatomic region (Study). RESULTS: Draft ROI guidelines were evaluated by 2 independent observers who registered weekly CBCT images to test their validity. Each observer assessed 5 patients per anatomic site, testing ROI options for accuracy of image registration and feasibility, while some ROI borders were adjusted based on algorithm matching performance. Validated ROI guidelines were presented to the sarcoma multidisciplinary site group, and an inter-professional committee of imaging experts for approval prior to clinical implementation (Act). CONCLUSION: ROI matching guidelines for STS IGRT were standardized for 4 anatomic sites using the PDSA cycle for change testing and implementation. IGRT guidelines are intended to improve STS image registration reproducibility, and in turn, are expected to improve the confidence of IGRT decision making and workflow efficiencies for a rare disease with diverse presentation.