Influence of planning time and treatment complexity on radiation therapy errors

Using standardized workflows and quantitative data-driven management to reduce time interval from simulation to treatment initiation

PURPOSE

External beam radiotherapy is a complex process, involving timely coordination among multiple teams. The aim of this study is to report our experience of establishing a standardized workflow and using quantitative data and metrics to manage the time-to-treatment initiation (TTI).

METHODS AND MATERIALS

Starting in 2014, we established a standard process in a radiation oncology-specific electronic medical record system (RO-EMR) for patients receiving external beam radiation therapy in our department, aiming to measure the time interval from simulation to treatment initiation, defined as TTI, for radiation oncology. TTI data were stratified according to the following treatment techniques: three-dimensional (3D) conformal therapy, intensity-modulated radiotherapy (IMRT), and stereotactic body radiotherapy (SBRT). Statistical analysis was performed with the Mann-Whitney test for the respective metrics of aggregate data for the initial period 2012- 2015 (PI) and the later period 2016-2019 (PII).

RESULT

Over 8 years, the average annual number of treatments for PI and PII were 1760 and 2357 respectively, with 3D, IMRT, and SBRT treatments accounting for 53, 29, 18% and 44, 34, 22%, respectively, of the treatment techniques. The median TTI for 3D, IMRT, and SBRT for PI and PII were 1, 6, 7, and 1, 5, 7 days, respectively, while the 90th percentile TTI for the three techniques in both periods were 5, 9, 11 and 4, 9, 10 days, respectively. From the aggregate data, the TTI was significantly reduced (p = 0.0004, p < 0.0001, p < 0.0001) from PI to PII for the three treatment techniques.

CONCLUSION

Establishing a standardized workflow and frequently measuring TTI resulted in shortening the TTI during the early years (in PI) and maintaining the established TTI in the subsequent years (in PII).

Interval From Simulation Imaging to Treatment Delivery in SABR of Lung Lesions: How Long is Too Long for the Lung?

Purpose

The purpose of this study was to evaluate the effect of delay between planning computed tomography (CT) used as a basis for treatment planning and the start of treatment (delay planning treatment [DPT]), on local control (LC) for lung lesions treated by SABR.

Methods and Materials

We pooled 2 databases from 2 monocentric retrospective analysis previously published and added planning CT and positron emission tomography (PET)-CT dates. We analyzed LC outcomes based on DPT and reviewed all available cofounding factors among demographic data and treatment parameters.

Results

A total of 210 patients with 257 lung lesions treated with SABR were evaluated. The median DPT was 14 days. Initial analysis revealed a discrepancy in LC as a function of DPT and a cutoff delay of 24 days (21 days for PET-CT almost systematically done 3 days after planning CT) was determined according to the Youden method. Cox model was applied to several predictors of local recurrence-free survival (LRFS). Univariate analysis showed LRFS decreasing significantly related to DPT ≥24 days (P = .0063), gross tumor volume, and clinical target volume (P = .0001 and P = .0022), but also with the presence of >1 lesion treated with the same planning CT (P = .024). LRFS increased significantly with higher biological effective dose (P < .0001). On multivariate analysis, LRFS remained significantly lower for lesions with DPT ≥24 days (hazard ratio, 2.113; 95% confidence interval, 1.097-4.795; P = .027).

Conclusions

DPT to SABR treatment delivery for lung lesions appears to reduce local control. Timing from imaging acquisition to treatment delivery should be systematically reported and tested in future studies. Our experience suggests that the time from planning imaging to treatment should be <21 days.

Fast VMAT planning for prostate radiotherapy: dosimetric validation of a deep learning-based initial segment generation method

Objective. To develop and evaluate a deep learning based fast volumetric modulated arc therapy (VMAT) plan generation method for prostate radiotherapy. Approach. A customized 3D U-Net was trained and validated to predict initial segments at 90 evenly distributed control points of an arc, linked to our research treatment planning system (TPS) for segment shape optimization (SSO) and segment weight optimization (SWO). For 27 test patients, the VMAT plans generated based on the deep learning prediction (VMATDL) were compared with VMAT plans generated with a previously validated automated treatment planning method (VMATref). For all test cases, the deep learning prediction accuracy, plan dosimetric quality, and the planning efficiency were quantified and analyzed. Main results. For all 27 test cases, the resulting plans were clinically acceptable. The V 95% for the PTV2 was greater than 99%, and the V 107% was below 0.2%. Statistically significant difference in target coverage was not observed between the VMATref and VMATDL plans (P = 0.3243 > 0.05). The dose sparing effect to the OARs between the two groups of plans was similar. Small differences were only observed for the Dmean of rectum and anus. Compared to the VMATref, the VMATDL reduced 29.3% of the optimization time on average. Significance. A fully automated VMAT plan generation method may result in significant improvement in prostate treatment planning efficiency. Due to the clinically acceptable dosimetric quality and high efficiency, it could potentially be used for clinical planning application and real-time adaptive therapy application after further validation.

Treatment Options in Early Stage (Stage I and II) of Oropharyngeal Cancer: A Narrative Review

Objective: to show an overview on the treatments’ options for stage I and II oropharyngeal carcinomasquamous cell carcinoma (OPSCC). Background: The traditional primary treatment modality of OPSCC at early stages is intensity modulated radiation therapy (IMRT). Trans-oral robotic surgery (TORS) has offered as an alternative, less invasive surgical option. Patients with human papilloma virus (HPV)-positive OPSCC have distinct staging with better overall survival in comparison with HPV-negative OPSCC patients. Methods: a comprehensive review of the English language literature was performed using PubMed, EMBASE, the Cochrane Library, and CENTRAL electronic databases. Conclusions: Many trials started examining the role of TORS in de-escalating treatment to optimize functional consequences while maintaining oncologic outcome. The head–neck surgeon has to know the current role of TORS in HPV-positive and negative OPSCC and the ongoing trials that will influence its future implementation. The feasibility of this treatment, the outcomes ensured, and the side effects are key factors to consider for each patient. The variables reported in this narrative review are pieces of a bigger puzzle called tailored, evidence-based driven medicine. Future evidence will help in the construction of robust and adaptive algorithms in order to ensure the adequate treatment for the OPSCC at early stages.

Medical physics external beam plan review: What contributes to the variability?

PURPOSE

In this article we report on the results of a survey of physics plan review practices conducted by the Cancer Care Ontario Communities of Practice and the variations in practice between and within centers.

METHODS

The medical physicists at each center worked together to complete the survey and submit a single response for that center. A 4-point Likert scale, used to report the variation in practice at each center, was quantified into two parameters: "Intra-center variation", the distribution of responses within the center, and "Variation between centers", the difference between the center's response and the provincial mean. These metrics were correlated with center characteristics to identify factors that impacted on variations in practice.

RESULTS

Bolus and heterogeneity correction were the only two items checked by all physicists in all centers. In more than half of the centers, image registration and DVH binning are not likely checked by physics. A significant difference in the variation between centers is observed for centers that used a single vendor's products. Centers that used an official checklist indicated higher levels and a wider range of Intra-center variation. Higher workload did not affect the variation in checking patterns between physicists in the same center.

CONCLUSIONS

The effect of a center's resources on their checking practice suggest that local environment and workflow be accounted for when implementing TG275 guidelines. The observation that standardized checklists did not reduce checking variability point to the importance of following the checklist development guidelines in MPPG4 to avoid ineffective checklists.

Volume-based algorithm of lung dose optimization in novel dynamic arc radiotherapy for esophageal cancer

This study aims to develop a volume-based algorithm (VBA) that can rapidly optimize rotating gantry arc angles and predict the lung V₅ preceding the treatment planning. This phantom study was performed in the dynamic arc therapy planning systems for an esophageal cancer model. The angle of rotation of the gantry around the isocenter as defined as arc angle (θ_A), ranging from 360° to 80° with an interval of 20°, resulting in 15 different θ_A of treatment plans. The corresponding predicted lung V₅ was calculated by the VBA, the mean lung dose, lung V₅, lung V₂₀, mean heart dose, heart V₃₀, the spinal cord maximum dose and conformity index were assessed from dose-volume histogram in the treatment plan. Correlations between the predicted lung V₅ and the dosimetric indices were evaluated using Pearson's correlation coefficient. The results showed that the predicted lung V₅ and the lung V₅ in the treatment plan were positively correlated (r = 0.996, p < 0.001). As the θ_A decreased, lung V₅, lung V₂₀, and the mean lung dose decreased while the mean heart dose, V₃₀ and the spinal cord maximum dose increased. The V₂₀ and the mean lung dose also showed high correlations with the predicted lung V₅ (r = 0.974, 0.999, p < 0.001). This study successfully developed an efficient VBA to rapidly calculate the θ_A to predict the lung V₅ and reduce the lung dose, with potentials to improve the current clinical practice of dynamic arc radiotherapy.

A Radiation Oncology-Specific Automated Trigger Indicator Tool for High-Risk, Near-Miss Safety Events

PURPOSE

Error detection in radiation oncology relies heavily on voluntary reporting, and many adverse events and near misses likely go undetected. Trigger tools use existing data in patient charts to identify otherwise-unaccounted-for events and have been successfully employed in other areas of medicine. We developed an automated radiation oncology-specific trigger tool and validated it against near-miss data from a high-volume incident learning system (ILS).

METHODS AND MATERIALS

Twenty triggers were derived from an electronic radiation oncology information system. Data from the systems over an approximately 3.5-year period were split randomly into training and test sets. The probability of a high-grade (grade 3-4) near miss for each treatment course in the training set was estimated using a regularized logistic regression model. The predictive model was applied to the test set. Records for 25 flagged treatment courses with an ILS entry were reviewed to explore the association between triggers and near misses, and 25 flagged courses without an ILS entry were reviewed to detect unreported near misses.

RESULTS

Of the 3159 treatment courses analyzed, 357 had a grade 3 to 4 ILS entry; 2210 courses composed the training set, and the test set had 949 courses. Areas under the curve on the training and test sets were 0.650 and 0.652, respectively. Of 20 triggers, 9 reached statistical significance on univariate analysis. Fifty percent of the 25 treatment courses in the test set with the highest predicted likelihood of a high-grade near miss with an ILS entry had a direct relationship between the triggers and the near miss. Review of the 25 treatment courses with the highest predicted likelihood of high-grade near miss without an ILS entry found 2 unreported near-miss events.

CONCLUSIONS

The radiation oncology-specific automated trigger tool performed modestly and identified additional treatment courses with near-miss events. Radiation oncology trigger tools deserve further exploration.

Technical Note: Assessing the performance of monthly CBCT image quality QA

PURPOSE

To assess the performance of routine cone-beam computed tomography (CBCT) quality assurance (QA) at predicting and diagnosing clinically recognizable linac CBCT image quality issues.

METHODS

Monthly automated linac CBCT image quality QA data were acquired on eight Varian linacs (Varian Medical Systems, Palo Alto, CA) using the CATPHAN 500 series phantom (The Phantom Laboratory, Inc., Greenwich, NY) and Total QA software (Image Owl, Inc., Greenwich, NY) over 34 months between July 2014 and May 2017. For each linac, the following image quality metrics were acquired: geometric distortion, spatial resolution, Hounsfield Unit (HU) constancy, uniformity, and noise. Quality control (QC) limits were determined by American Association of Physicists in Medicine (AAPM) expert consensus documents Task Group (TG-142 and TG-179) and the manufacturer acceptance testing procedure. Clinically recognizable CBCT issues were extracted from the in-house incident learning system (ILS) and service reports. The sensitivity and specificity of CATPHAN QA at predicting clinically recognizable image quality issues was investigated. Sensitivity was defined as the percentage of clinically recognizable CBCT image quality issues that followed a failing CATPHAN QA. Quality assurance results are categorized as failing if one or more image quality metrics are outside the QC limits. The specificity of CATPHAN QA was defined as one minus the fraction of failing CATPHAN QA results that did not have a clinically recognizable CBCT image quality issue in the subsequent month. Receiver operating characteristic (ROC) curves were generated for each image quality metric by plotting the true positive rate (TPR) against the false-positive rate (FPR).

RESULTS

Over the study period, 18 image quality issues were discovered by clinicians while using CBCT to set up the patient and five were reported prior to x-ray tube repair. The incidents ranged from ring artifacts to uniformity problems. The sensitivity of the TG-142/179 limits was 17% (four of the prior monthly QC tests detected a clinically recognizable image quality issue). The area under the curve (AUC) calculated for each image quality metric ROC curve was: 0.85 for uniformity, 0.66 for spatial resolution, 0.51 for geometric distortion, 0.56 for noise, 0.73 for HU constancy, and 0.59 for contrast resolution.

CONCLUSION

Automated monthly QA is not a good predictor of CBCT image quality issues. Of the available metrics, uniformity has the best predictive performance, but still has a high FPR and low sensitivity. The poor performance of CATPHAN QA as a predictor of image quality problems is partially due to its reliance on region-of-interest (ROI) based algorithms and a lack of a global algorithm such as correlation. The manner in which image quality issues occur (trending toward failure or random) is still not known and should be studied further. CBCT image quality QA should be adapted based on how CBCT is used clinically.

Risk factors for near-miss events and safety incidents in pediatric radiation therapy

BACKGROUND AND PURPOSE

Factors contributing to safety- or quality-related incidents (e.g. variances) in children are unknown. We identified clinical and RT treatment variables associated with risk for variances in a pediatric cohort.

MATERIALS AND METHODS

Using our institution's incident learning system, 81 patients age ≤21 years old who experienced variances were compared to 191 pediatric patients without variances. Clinical and RT treatment variables were evaluated as potential predictors for variances using univariate and multivariate analyses.

RESULTS

Variances were primarily documentation errors (n = 46, 57%) and were most commonly detected during treatment planning (n = 14, 21%). Treatment planning errors constituted the majority (n = 16 out of 29, 55%) of near-misses and safety incidents (NMSI), which excludes workflow incidents. Therapists reported the majority of variances (n = 50, 62%). Physician cross-coverage (OR = 2.1, 95% CI = 1.04-4.38) and 3D conformal RT (OR = 2.3, 95% CI = 1.11-4.69) increased variance risk. Conversely, age >14 years (OR = 0.5, 95% CI = 0.28-0.88) and diagnosis of abdominal tumor (OR = 0.2, 95% CI = 0.04-0.59) decreased variance risk.

CONCLUSIONS

Variances in children occurred in early treatment phases, but were detected at later workflow stages. Quality measures should be implemented during early treatment phases with a focus on younger children and those cared for by cross-covering physicians.

Incident learning in radiation oncology: A review

Incident learning is a key component for maintaining safety and quality in healthcare. Its use is well established and supported by professional society recommendations, regulations and accreditation, and objective evidence. There is an active interest in incident learning systems (ILS) in radiation oncology, with over 40 publications since 2010. This article is intended as a comprehensive topic review of ILS in radiation oncology, including history and summary of existing literature, nomenclature and categorization schemas, operational aspects of ILS at the institutional level including event handling and root cause analysis, and national and international ILS for shared learning. Core principles of patient safety in the context of ILS are discussed, including the systems view of error, culture of safety, and contributing factors such as cognitive bias. Finally, the topics of medical error disclosure and second victim syndrome are discussed. In spite of the rapid progress and understanding of ILS, challenges remain in applying ILS to the radiation oncology context. This comprehensive review may serve as a springboard for further work.

Clinical outcomes of helical conformal versus nonconformal palliative radiation therapy for axial skeletal metastases

PURPOSE

Palliative radiation therapy (RT) for bone metastases has traditionally been delivered with conventional, nonconformal RT (NCRT). Conformal RT (CRT) is potentially more complex and expensive than NCRT, but may reduce normal tissue dose and subsequently toxicity. In this retrospective analysis, we compared CRT with NCRT to investigate the association between conformality and toxicity.

METHODS AND MATERIALS

A retrospective analysis of patients receiving palliative RT for axial skeletal bone metastases from 2012 to 2014 was conducted. Patient and treatment characteristics were obtained including dosimetric variables, acute toxicity, and subjective pain during treatment and in the acute posttreatment period (≤60 days after completion). Statistical analyses included t tests, χ² tests, and multivariate logistic regression.

RESULTS

A total of 179 patients and 254 bone metastases were identified (142 CRT, 112 NCRT). The CRT and NCRT groups were well matched for baseline characteristics (number of fractions, field size, treatment sites, and concurrent chemotherapy). In multivariate logistic regression models, technique (CRT vs NCRT) was not associated with development of acute toxicity. Regarding toxicity, Eastern Cooperative Oncology Group performance status and total dose were significantly associated with a higher rate of acute toxicity during RT (odds ratios, 0.649 and 1.129 and P = .027 and .044, respectively), and only a higher number of vertebral bodies in the treatment field was significantly associated with acute toxicity post-treatment (odds ratios, 1.219, P = .028). CRT was associated with improvement in bone pain during and posttreatment (P = .049 and .045, respectively).

CONCLUSIONS

Our results demonstrate no difference in acute toxicity following palliative RT with CRT compared with NCRT for painful bone metastases; however, treatment volume did predict for increased toxicity. Larger studies may further elucidate the value of CRT including the impact of dose escalation for bone metastases and differences in patient reported outcomes between RT techniques.

Are we making an impact with incident learning systems? Analysis of quality improvement interventions using total body irradiation as a model system

PURPOSE

Despite increasing interest in incident learning systems (ILS) to improve safety and quality in radiation oncology, little is known about interventions developed in response to safety data. We used total body irradiation (TBI) as a model system to study the effectiveness of interventions from our institutional ILS.

METHODS AND MATERIALS

Near-miss event reports specific to TBI were identified from a departmental ILS from March 2012 to December 2015. The near-miss risk index was rated at multidisciplinary review from 0 (no potential harm) to 4 (critical potential harm). Interventions were analyzed for effectiveness with a schema adapted from The Joint Commission and other agencies: "most reliable" (eg, forcing functions, automation), "somewhat reliable" (eg, checklists, standardization), and "least reliable" (eg, training, rules, procedures). Causal factors of each event were drawn from the casual factor schema used in radiation oncology ILS.

RESULTS

Of 4007 safety-related reports, 266 reports pertained to TBI. TBI reports had a somewhat higher proportion of high-risk events (near-miss risk index 3-4) compared with non-TBI reports (25% vs 17%, P = .0045). A total of 117 interventions were implemented. The reliability indicators for the interventions were: most reliable (11% of interventions), somewhat reliable (17%), and least reliable (72%). Interventions were more likely to be applied to high-risk events (54% vs 41%, P = .03). There was a pattern of high-reliability interventions with increased risk score of events. Events involving human error (eg, slips) and equipment/information technology lent themselves more often to high-reliability interventions. Events related to communication, standardization, and training were associated with low-reliability interventions.

CONCLUSIONS

Over a 3.5-year period, 117 quality improvement strategies were developed for TBI based on ILS. Interventions were more likely to be applied to high-risk events and high-risk events were more likely to be associated with high-quality interventions. These results may be useful to institutions seeking to develop interventions based on ILS data.

Safety Considerations in Stereotactic Body Radiation Therapy

Although many error pathways are common to both stereotactic body radiation therapy (SBRT) and conventional radiation therapy, SBRT presents a special set of challenges including short treatment courses and high-doses, an enhanced reliance on imaging, technical challenges associated with commissioning, special resource requirements for staff and training, and workflow differences. Emerging data also suggest that errors occur at a higher rate in SBRT treatments. Furthermore, when errors do occur they often have a greater effect on SBRT treatments. Given these challenges, it is important to understand and employ systematic approaches to ensure the quality and safety of SBRT treatment. Here, we outline the pathways by which error can occur in SBRT, illustrated through a series of case studies, and highlight 9 specific well-established tools to either reduce error or minimize its effect to the patient or both.