M. Nyflot

Challenges and opportunities in patient-specific, motion-managed and PET/CT-guided radiation therapy of lung cancer: review and perspective

The increasing interest in combined positron emission tomography (PET) and computed tomography (CT) to guide lung cancer radiation therapy planning has been well documented. Motion management strategies during treatment simulation PET/CT imaging and treatment delivery have been proposed to improve the precision and accuracy of radiotherapy. In light of these research advances, why has translation of motion-managed PET/CT to clinical radiotherapy been slow and infrequent? Solutions to this problem are as complex as they are numerous, driven by large inter-patient variability in tumor motion trajectories across a highly heterogeneous population. Such variation dictates a comprehensive and patient-specific incorporation of motion management strategies into PET/CT-guided radiotherapy rather than a one-size-fits-all tactic. This review summarizes challenges and opportunities for clinical translation of advances in PET/CT-guided radiotherapy, as well as in respiratory motion-managed radiotherapy of lung cancer. These two concepts are then integrated into proposed patient-specific workflows that span classification schemes, PET/CT image formation, treatment planning, and adaptive image-guided radiotherapy delivery techniques.

Targeting safety improvements through identification of incident origination and detection in a near-miss incident learning system.

PURPOSEnRadiation treatment planning involves a complex workflow that has multiple potential points of vulnerability. This study utilizes an incident reporting system to identify the origination and detection points of near-miss errors, in order to guide their departmental safety improvement efforts. Previous studies have examined where errors arise, but not where they are detected or applied a near-miss risk index (NMRI) to gauge severity.nnnMETHODSnFrom 3/2012 to 3/2014, 1897 incidents were analyzed from a departmental incident learning system. All incidents were prospectively reviewed weekly by a multidisciplinary team and assigned a NMRI score ranging from 0 to 4 reflecting potential harm to the patient (no potential harm to potential critical harm). Incidents were classified by point of incident origination and detection based on a 103-step workflow. The individual steps were divided among nine broad workflow categories (patient assessment, imaging for radiation therapy (RT) planning, treatment planning, pretreatment plan review, treatment delivery, on-treatment quality management, post-treatment completion, equipment/software quality management, and other). The average NMRI scores of incidents originating or detected within each broad workflow area were calculated. Additionally, out of 103 individual process steps, 35 were classified as safety barriers, the process steps whose primary function is to catch errors. The safety barriers which most frequently detected incidents were identified and analyzed. Finally, the distance between event origination and detection was explored by grouping events by the number of broad workflow area events passed through before detection, and average NMRI scores were compared.nnnRESULTSnNear-miss incidents most commonly originated within treatment planning (33%). However, the incidents with the highest average NMRI scores originated during imaging for RT planning (NMRI = 2.0, average NMRI of all events = 1.5), specifically during the documentation of patient positioning and localization of the patient. Incidents were most frequently detected during treatment delivery (30%), and incidents identified at this point also had higher severity scores than other workflow areas (NMRI = 1.6). Incidents identified during on-treatment quality management were also more severe (NMRI = 1.7), and the specific process steps of reviewing portal and CBCT images tended to catch highest-severity incidents. On average, safety barriers caught 46% of all incidents, most frequently at physics chart review, therapists chart check, and the review of portal images; however, most of the incidents that pass through a particular safety barrier are not designed to be capable of being captured at that barrier.nnnCONCLUSIONSnIncident learning systems can be used to assess the most common points of error origination and detection in radiation oncology. This can help tailor safety improvement efforts and target the highest impact portions of the workflow. The most severe near-miss events tend to originate during simulation, with the most severe near-miss events detected at the time of patient treatment. Safety barriers can be improved to allow earlier detection of near-miss events.

The effectiveness of pretreatment physics plan review for detecting errors in radiation therapy

PURPOSEnThe pretreatment physics plan review is a standard tool for ensuring treatment quality. Studies have shown that the majority of errors in radiation oncology originate in treatment planning, which underscores the importance of the pretreatment physics plan review. This quality assurance measure is fundamentally important and central to the safety of patients and the quality of care that they receive. However, little is known about its effectiveness. The purpose of this study was to analyze reported incidents to quantify the effectiveness of the pretreatment physics plan review with the goal of improving it.nnnMETHODSnThis study analyzed 522 potentially severe or critical near-miss events within an institutional incident learning system collected over a three-year period. Of these 522 events, 356 originated at a workflow point that was prior to the pretreatment physics plan review. The remaining 166 events originated after the pretreatment physics plan review and were not considered in the study. The applicable 356 events were classified into one of the three categories: (1) events detected by the pretreatment physics plan review, (2) events not detected but potentially detectable by the physics review, and (3) events not detectable by the physics review. Potentially detectable events were further classified by which specific checks performed during the pretreatment physics plan review detected or could have detected the event. For these events, the associated specific check was also evaluated as to the possibility of automating that check given current data structures. For comparison, a similar analysis was carried out on 81 events from the international SAFRON radiation oncology incident learning system.nnnRESULTSnOf the 356 applicable events from the institutional database, 180/356 (51%) were detected or could have been detected by the pretreatment physics plan review. Of these events, 125 actually passed through the physics review; however, only 38% (47/125) were actually detected at the review. Of the 81 events from the SAFRON database, 66/81 (81%) were potentially detectable by the pretreatment physics plan review. From the institutional database, three specific physics checks were particularly effective at detecting events (combined effectiveness of 38%): verifying the isocenter (39/180), verifying DRRs (17/180), and verifying that the plan matched the prescription (12/180). The most effective checks from the SAFRON database were verifying that the plan matched the prescription (13/66) and verifying the field parameters in the record and verify system against those in the plan (23/66). Software-based plan checking systems, if available, would have potential effectiveness of 29% and 64% at detecting events from the institutional and SAFRON databases, respectively.nnnCONCLUSIONSnPretreatment physics plan review is a key safety measure and can detect a high percentage of errors. However, the majority of errors that potentially could have been detected were not detected in this study, indicating the need to improve the pretreatment physics plan review performance. Suggestions for improvement include the automation of specific physics checks performed during the pretreatment physics plan review and the standardization of the review process.

Contribution of submandibular gland and swallowing structure sparing to post-radiation therapy PEG dependence in oropharynx cancer patients treated with split-neck IMRT technique

BackgroundRadiation therapy-related dysphagia is worsened by xerostomia. The submandibular glands (SMG) produce saliva rich in lubricating mucins, and sparing the SMG has been shown to reduce xerostomia. The goal of this study was to determine whether SMG sparing IMRT is associated with reduced post-treatment PEG dependence in locally advanced oropharynx cancer patients.MethodsPatients treated with definitive radiation therapy for oropharynx cancer were included in this retrospective study. Those with disease recurrence were excluded. Salivary glands and swallowing-related organs at risk, including pharyngeal constrictors, were contoured. Primary endpoint was time from end of radiation treatment to freedom from gastrostomy (PEG) tube dependence. Cox proportional hazards regression and logistic regression were used to assess influence of normal tissue doses on swallowing related endpoints.ResultsSixty-nine patients were included. All had stage III/IV disease and 97% received concurrent systemic therapy. Fifty-seven percent had contralateral SMG (cSMG) mean dose <50xa0Gy, a level shown to predict for xerostomia. Eighty four percent of patients had a PEG tube placed electively. On univariate analysis, the strongest predictor of time to freedom from PEG tube dependence was cSMG dose (HR 0.97 per Gy (95% CI 0.95–0.98), pu2009<u20090.0001). This relationship persisted on multivariate analysis (pu2009=u20090.052). The dose to superior and middle pharyngeal constrictor muscles, and larynx were also significant on univariate analysis. Patients with cSMG dose less than median (42xa0Gy, nu2009=u200934) had a significantly shorter time to freedom from PEG dependence: median 1.9 vs. 3.5xa0months, pu2009<u20090.0001. At 6xa0months, 3% of patients with cSMG doseu2009<u200942xa0Gy were PEG dependent compared to 31% with cSMG doseu2009>u200942xa0Gy (pu2009=u20090.002).ConclusionsPatients treated with cSMG sparing radiotherapy had significantly shorter time to PEG tube removal after treatment, suggesting a clinically meaningful reduction in subacute dysphagia compared to non-cSMG sparing treatment.

Best practices for safety improvement through high-volume institutional incident learning: lessons learned from 2 years

ObjectiveIncident learning systems (ILSs) are a key component of improving patient safety in radiation oncology, but the practicalities of ILS implementation can present major challenges. We describe the implementation and best practices derived from 2xa0years of experience with institutional incident learning, with details on root cause analysis (RCA), a list of key process improvements, and operational aspects of ILS use.Methods and materialsThe structure of the ILS is consistent with recommendations from the American Association of Physicists in Medicine (AAPM). Workflow is analyzed for incident reports from initial reporting to analysis and feedback to the reporter, including staffing required. A system for incident categorization is shown, as well as sample events selected for root cause analysis, and suggestions for providing feedback to users of ILS.ResultsIn the first 2xa0years of the ILS implementation from 2012 to 2014, 1897 near-miss incidents were reported. There is widespread participation in the ILS program across all professional groups inside the department, with at least 75xa0% of clinical staff having filed at least one report. Total workload for the ILS program is estimated to be approximately one full-time employee, shared by approximately eight team members. Fifteen events were selected for RCA during this period. Eighteen major process improvement projects are described, ranging from issues related to process standardization, automation, staffing, new organization structures, and equipment purchase.ConclusionsA unique high reporting volume institutional ILS has successfully resulted in numerous improvements in process, safety, and quality. Details for implementation and best practices for incident learning have been presented to allow adaptation in other practices.

The Relationship Between Cardiac Radiation Dose and Mediastinal Lymph Node Involvement in Stage III Non-Small Cell Lung Cancer Patients

Purpose The results from Radiation Therapy Oncology Group (RTOG) 0617, a dose escalation trial that compared treatment with 60 Gy versus 74 Gy for patients with stage III non-small cell lung cancer (NSCLC), suggested that in these patients, the heart dose from radiation therapy correlates with survival. In particular, the study noted that patients with a high heart V5 and V30 had a poorer overall survival; however, the exact cause of this correlation is not known. We hypothesize that heart dose may be a surrogate for mediastinal nodal involvement, which has prognostic value in NSCLC. This study evaluates the relationship between heart dose and involvement of mediastinal lymph nodes in patients with stage III NSCLC treated with radiation therapy. Methods and materials A total of 56 patients were identified and treated with definitive radiation therapy from 2007 to 2014. The heart was recontoured for every patient by a single physician, per the RTOG 1106 contouring atlas. We assessed lymph node station involvement using pretreatment data, and nodal coverage was confirmed on plan review. Results Mean heart dose was found to be significantly higher in patients with multinodal station and level 7 involvement. On Spearmans rank correlation, level 7 was significantly associated with all heart parameters tested (P < .001). Patients who had 2 or more lymph node stations involved were found to have significantly higher heart doses for all parameters tested when compared with those who had only one station involved or no nodal involvement. Conclusions Our findings suggest that heart dose may be a surrogate for other prognostic factors in stage III NSCLC rather than an independent predictor of outcome.

SU-D-201-07: A Survey of Radiation Oncology Residents' Training and Preparedness to Lead Patient Safety Programs in Clinics.

PURPOSEnSafety and quality has garnered increased attention in radiation oncology, and physicians and physicists are ideal leaders of clinical patient safety programs. However, it is not clear whether residency programs incorporate formal patient safety training and adequately equip residents to assume this leadership role. A national survey was conducted to evaluate medical and physics residents exposure to safety topics and their confidence with the skills required to lead clinical safety programs.nnnMETHODSnRadiation oncology residents were identified in collaboration with ARRO and AAPM. The survey was released in February 2016 via email using REDCap. This included questions about exposure to safety topics, confidence leading safety programs, and interest in training opportunities (i.e. workshops). Residents rated their exposure, skills, and confidence on 4 or 5-point scales. Medical and physics residents responses were compared using chi-square tests.nnnRESULTSnResponses were collected from 56 of 248 (22%) physics and 139 of 690 (20%) medical residents. More than two thirds of all residents had no or only informal exposure to incident learning systems (ILS), root cause analysis (RCA), failure mode and effects analysis (FMEA), and the concept of human factors engineering (HFE). Likewise, 63% of residents had not heard of RO-ILS. Response distributions were similar, however more physics residents had formal exposure to FMEA (p<0.0001) and felt they were adequately trained to lead FMEAs in clinic (p<0.001) than medical residents. Only 36% of residents felt their patient safety training was adequate, and 58% felt more training would benefit their education.nnnCONCLUSIONnThese results demonstrate that, despite increasing desire for patient safety training, medical and physics residents exposure to relevant concepts is low. Physics residents had more exposure to FMEA than medical residents, and were more confident in leading FMEA. This suggests that increasing resident exposure to specific topics may increase their confidence.

TU-F-12A-05: Sensitivity of Textural Features to 3D Vs. 4D FDG-PET/CT Imaging in NSCLC Patients

PURPOSEnNeighborhood Gray-level difference matrices (NGLDM) based texture parameters extracted from conventional (3D) 18F-FDG PET scans in patients with NSCLC have been previously shown to associate with response to chemoradiation and poorer patient outcome. However, the change in these parameters when utilizing respiratory-correlated (4D) FDG-PET scans has not yet been characterized for NSCLC. The Objectives: of this study was to assess the extent to which NGLDM-based texture parameters on 4D PET images vary with reference to values derived from 3D scans in NSCLC.nnnMETHODSnEight patients with newly diagnosed NSCLC treated with concomitant chemoradiotherapy were included in this study. 4D PET scans were reconstructed with OSEM-IR in 5 respiratory phase-binned images and corresponding CT data of each phase were employed for attenuation correction. NGLDM-based texture features, consisting of coarseness, contrast, busyness, complexity and strength, were evaluated for gross tumor volumes defined on 3D/4D PET scans by radiation oncologists. Variation of the obtained texture parameters over the respiratory cycle were examined with respect to values extracted from 3D scans.nnnRESULTSnDifferences between texture parameters derived from 4D scans at different respiratory phases and those extracted from 3D scans ranged from -30% to 13% for coarseness, -12% to 40% for contrast, -5% to 50% for busyness, -7% to 38% for complexity, and -43% to 20% for strength. Furthermore, no evident correlations were observed between respiratory phase and 4D scan texture parameters.nnnCONCLUSIONnResults of the current study showed that NGLDM-based texture parameters varied considerably based on choice of 3D PET and 4D PET reconstruction of NSCLC patient images, indicating that standardized image acquisition and analysis protocols need to be established for clinical studies, especially multicenter clinical trials, intending to validate prognostic values of texture features for NSCLC.

SU‐E‐T‐232: Safety and Quality Improvements in a Pediatric Total Body Irradiation Procedure

Purpose: Through the use of incident learning, safety‐critical areas were identified in our current procedure for pediatric patients undergoing total body irradiation (TBI) for bone‐marrow transplant. These are relatively rare and complex procedures requiring non‐standard setups and administration of anesthesia. The purpose of this study is to simplify and standardize the simulation and planning procedure for pediatric TBI to improve the safety and quality of care. Methods: Motivated by near‐miss incidents, a systematic review of current TBI procedures was conducted, and the following issues were identified: unclear communication describing variations in setup at simulation versus treatment related to anesthesia requirements, confusion about measurement units, unclear criteria for various setup options to accommodate patients ranging in age from infancy to 7 years, and variations in compensator design methods. To address these issues, a simulation form was designed with detailed instructions and documentation requirements. Dose calculation and tissue compensation procedures were redesigned to remove set‐up variations. Calculations were performed on 28 previously‐treated patients to determine the dose uniformity with the new vs. old method. Results: Feedback from clinical staff indicates that the new simulation form improves interdepartmental communication and decreases the risk of treating patients in a setup that differs from that used during the simulation. The new compensator design significantly improved patient dose uniformity: 0.8±0.4% (new method) vs. 4.2±2.3% (old method) (p < 0.01). The data indicates the new compensator design will Results in fewer out‐of‐tolerance in vivo dosimetry readings and reduce associated re‐planning efforts, which is especially critical for single‐fraction treatment. Conclusion: For an institution averaging one pediatric TBI case per month, standardization of the procedure simplifies the planning process and improves patient safety. Since there are few technical reports about pediatric TBI, this experience may be especially beneficial for other centers with low volumes of pediatric TBI patients.

TU-E-141-09: Impact of Attenuation Correction Mode On 4D PET/CT for Target Definition in Lung Cancer Patients

PURPOSEnThe impact of attenuation correction on respiratory-gated (4D) PET/CT images to define lung cancer targets, relative to 4D maximum intensity projection (MIP) or 3D static images, is poorly understood. Changes from 3DPET to 4DPET SUV metrics and target volumes were characterized in patients as a function of PET acquisition and CT attenuation correction (CTAC).nnnMETHODSnLung cancer patients underwent PET/CT list-mode examinations spanning 3 bed positions. Static and respiratory phase-gated sinograms were unlisted to generate 3DPET and 4DPET images. Emission data were attenuation-corrected with phase-averaged (4DAVG) or phase-matched (4DMATCH) 4DCT and reconstructed with OSEM (2 iterations, 28 subsets, 5 mm post-filter) on 2.0×2.0×3.3 mm3 voxel grids. PET target volumes were defined in MIM™5.6.3 using a gradient search method. Differences in SUVmax, SUVmean, SUVpeak, and defined volumes were compared between 3D, 4D MIP, and individual 4D phases by pairwise sign-rank tests. 4DAVG and 4DMATCH CTAC-PET image metrics were compared between respiratory phases using multi-group non-parametric ANOVA.nnnRESULTSnFor 13 FDG-PET avid lesions, SUVmax, SUVmean and SUVpeak were significantly higher in 4DMIP and 4D phase-gated images relative to 3D images (9-11%, p<0.03). 4DMIP volumes were larger than 3D and 4D phase volumes (6-14%, p<0.01). 4DMATCH SUVmax was higher than 4DAVG SUVmax near end-expiration phase and lower around peak-inspiration phase (p=0.001). 4DMATCH SUVmean exceeded 4DAVG SUVmean at end-expiration (p=0.02), while SUVpeak trended similarly but was insufficiently powered (p=0.06). 4D phase volumes were not significantly different between attenuation correction methods (p>0.37).nnnCONCLUSIONn4DPET provides improved image quantification over 3DPET. 4DPET quantification near end-expiration appears superior with phase-matched CTAC, but may be less reliable during phase-gates with residual motion and phase-sorting CT artifacts. Optimization of CTAC from patient-specific respiratory patterns may improve robustness of 4D PET/CT for lung cancer target definition and dose painting.