First clinical implementation of real-time, real anatomy tracking and radiation beam control

PURPOSE

We describe the acceptance testing, commissioning, periodic quality assurance, and workflow procedures developed for the first clinically implemented magnetic resonance imaging-guided radiation therapy (MR-IGRT) system for real-time tracking and beam control.

METHODS

The system utilizes real-time cine imaging capabilities at 4 frames per second for real-time tracking and beam control. Testing of the system was performed using an in-house developed motion platform and a commercially available motion phantom. Anatomical tracking is performed by first identifying a target (a region of interest that is either tissue to be treated or a critical structure) and generating a contour around it. A boundary contour is also created to identify tracking margins. The tracking algorithm deforms the anatomical contour (target or a normal organ) on every subsequent cine frame and compares it to the static boundary contour. If the anatomy of interest moves outside the boundary, the radiation delivery is halted until the tracked anatomy returns to treatment portal. The following were performed to validate and clinically implement the system: (a) spatial integrity evaluation; (b) tracking accuracy; (c) latency; (d) relative point dose and spatial dosimetry; (e) development of clinical workflow for gating; and (f) independent verification by an outside credentialing service.

RESULTS

The spatial integrity of the MR system was found to be within 2 mm over a 45-cm diameter field-of-view. The tracking accuracy for geometric targets was within 1.2 mm. The average system latency was measured to be within 394 ms. The dosimetric accuracy using ionization chambers was within 1.3% ± 1.7%, and the dosimetric spatial accuracy was within 2 mm. The phantom irradiation for the outside credentialing service had satisfactory results, as well.

CONCLUSIONS

The first clinical MR-IGRT system was validated for real-time tracking and gating capabilities and shown to be reliable and accurate. Patient workflow methods were developed for efficient treatment. Periodic quality assurance tests can be efficiently performed with commercially available equipment to ensure accurate system performance.

CAPTURE: Consistently Acquired Projections for Tuned and Robust Estimation: A Self-Navigated Respiratory Motion Correction Approach

OBJECTIVES

In this study, we present a fully automated and robust self-navigated approach to obtain 4-dimensional (4-D) motion-resolved images during free breathing.

MATERIALS AND METHODS

The proposed method, Consistently Acquired Projections for Tuned and Robust Estimation (CAPTURE), is a variant of the stack-of-stars gradient-echo sequence. A 1-D navigator was consistently acquired at a fixed azimuthal angle for all stacks of spokes to reduce nonphysiological signal contamination due to system imperfections. The resulting projections were then "tuned" using complex phase rotation to adapt to scan-to-scan variations, followed by the detection of the respiratory curve. Four-dimensional motion-corrected and uncorrected images were then reconstructed via respiratory and temporal binning, respectively.This Health Insurance Portability and Accountability Act-compliant study was performed with Institutional Review Board approval. A phantom experiment was performed using a custom-made deformable motion phantom with an adjustable frequency and amplitude. For in vivo experiments, 10 healthy participants and 12 liver tumor patients provided informed consent and were imaged with the CAPTURE sequence.Two radiologists, blinded to which images were motion-corrected and which were not, independently reviewed the images and scored the image quality using a 5-point Likert scale.

RESULTS

In the respiratory motion phantom experiment, CAPTURE reversed the effects of motion blurring and restored edge sharpness from 36% to 78% of that observed in the images from the static scan.Despite large intra- and intersubject variability in respiration patterns, CAPTURE successfully detected the respiratory motion signal in all participants and significantly improved the image quality according to the subjective radiological assessments of 2 raters (P < 0.05 for both raters) with a 1 to 2-point improvement in the median Likert scores across the whole set of participants. Small lesions (<1 cm in size) which might otherwise be missed on uncorrected images because of motion blurring were more clearly depicted on the CAPTURE images.

CONCLUSIONS

CAPTURE provides a robust and fully automated solution for obtaining 4-D motion-resolved images in a free-breathing setting. With its unique tuning feature, CAPTURE can adapt to large intersubject and interscan variations. CAPTURE also enables better lesion delineation because of improved image sharpness, thereby increasing the visibility of small lesions.

Multi institutional quantitative phantom study of yttrium-90 PET in PET/MRI: the MR-QUEST study

Background

Yttrium-90 (⁹⁰Y) radioembolization involves the intra-arterial delivery of radioactive microspheres to treat hepatic malignancies. Though this therapy involves careful pre-treatment planning and imaging, little is known about the precise location of the microspheres once they are administered. Recently, there has been growing interest post-radioembolization imaging using positron-emission tomography (PET) for quantitative dosimetry and identifying lesions that may benefit from additional salvage therapy. In this study, we aim to measure the inter-center variability of ⁹⁰Y PET measurements as measured on PET/MRI in preparation for a multi-institutional prospective phase I/II clinical trial.

Eight institutions participated in this study and followed a standardized phantom filling and imaging protocol. The NEMA NU2-2012 body phantom was filled with 3 GBq of ⁹⁰Y chloride solution. The phantom was imaged for 30 min in listmode on a Siemens Biograph mMR non-TOF PET/MRI scanner at five time points across 10 days (0.3–3.0 GBq). Raw PET data were sent to a central site for image reconstruction and data analysis. Images were reconstructed with optimal parameters determined from a previous study. Volumes of interest (VOIs) matching the known sphere diameters were drawn on the vendor-provided attenuation map and propagated to the PET images. Recovery coefficients (RCs) and coefficient of variation of the RCs (COV) were calculated from these VOIs for each sphere size and activity level.

Results

Mean RCs ranged from 14.5 to 75.4%, with the lowest mean RC coming from the smallest sphere (10 mm) on the last day of imaging (0.16 MBq/ml) and the highest mean RC coming from the largest sphere (37 mm) on the first day of imaging (2.16 MBq/ml). The smaller spheres tended to exhibit higher COVs. In contrast, the larger spheres tended to exhibit lower COVs. COVs from the 37 mm sphere were < 25.3% in all scans. For scans with ≥ 0.60 MBq/ml, COVs were ≤ 25% in spheres ≥ 22 mm. However, for all other spheres sizes and activity levels, COVs were usually > 25%.

Conclusions

Post-radioembolization dosimetry of lesions or other VOIs ≥ 22 mm in diameter can be consistently obtained (< 25% variability) at a multi-institutional level using PET/MRI for any clinically significant activity for ⁹⁰Y radioembolization.

Optimization of treatment planning workflow and tumor coverage during daily adaptive magnetic resonance image guided radiation therapy (MR-IGRT) of pancreatic cancer

BACKGROUND

To simplify the adaptive treatment planning workflow while achieving the optimal tumor-dose coverage in pancreatic cancer patients undergoing daily adaptive magnetic resonance image guided radiation therapy (MR-IGRT).

METHODS

In daily adaptive MR-IGRT, the plan objective function constructed during simulation is used for plan re-optimization throughout the course of treatment. In this study, we have constructed the initial objective functions using two methods for 16 pancreatic cancer patients treated with the ViewRay™ MR-IGRT system: 1) the conventional method that handles the stomach, duodenum, small bowel, and large bowel as separate organs at risk (OARs) and 2) the OAR grouping method. Using OAR grouping, a combined OAR structure that encompasses the portions of these four primary OARs within 3 cm of the planning target volume (PTV) is created. OAR grouping simulation plans were optimized such that the target coverage was comparable to the clinical simulation plan constructed in the conventional manner. In both cases, the initial objective function was then applied to each successive treatment fraction and the plan was re-optimized based on the patient's daily anatomy. OAR grouping plans were compared to conventional plans at each fraction in terms of coverage of the PTV and the optimized PTV (PTV OPT), which is the result of the subtraction of overlapping OAR volumes with an additional margin from the PTV.

RESULTS

Plan performance was enhanced across a majority of fractions using OAR grouping. The percentage of the volume of the PTV covered by 95% of the prescribed dose (D₉₅) was improved by an average of 3.87 ± 4.29% while D₉₅ coverage of the PTV OPT increased by 3.98 ± 4.97%. Finally, D₁₀₀ coverage of the PTV demonstrated an average increase of 6.47 ± 7.16% and a maximum improvement of 20.19%.

CONCLUSIONS

In this study, our proposed OAR grouping plans generally outperformed conventional plans, especially when the conventional simulation plan favored or disregarded an OAR through the assignment of distinct weighting parameters relative to the other critical structures. OAR grouping simplifies the MR-IGRT adaptive treatment planning workflow at simulation while demonstrating improved coverage compared to delivered pancreatic cancer treatment plans in daily adaptive radiation therapy.

Automatic online and real-time tumour motion monitoring during stereotactic liver treatments on a conventional linac by combined optical and sparse monoscopic imaging with kilovoltage x-rays (COSMIK)

The purpose of this study was to develop, validate and clinically demonstrate fully automatic tumour motion monitoring on a conventional linear accelerator by combined optical and sparse monoscopic imaging with kilovoltage x-rays (COSMIK). COSMIK combines auto-segmentation of implanted fiducial markers in cone-beam computed tomography (CBCT) projections and intra-treatment kV images with simultaneous streaming of an external motion signal. A pre-treatment CBCT is acquired with simultaneous recording of the motion of an external marker block on the abdomen. The 3-dimensional (3D) marker motion during the CBCT is estimated from the auto-segmented positions in the projections and used to optimize an external correlation model (ECM) of internal motion as a function of external motion. During treatment, the ECM estimates the internal motion from the external motion at 20 Hz. KV images are acquired every 3 s, auto-segmented, and used to update the ECM for baseline shifts between internal and external motion. The COSMIK method was validated using Calypso-recorded internal tumour motion with simultaneous camera-recorded external motion for 15 liver stereotactic body radiotherapy (SBRT) patients. The validation included phantom experiments and simulations hereof for 12 fractions and further simulations for 42 fractions. The simulations compared the accuracy of COSMIK with ECM-based monitoring without model updates and with model updates based on stereoscopic imaging as well as continuous kilovoltage intrafraction monitoring (KIM) at 10 Hz without an external signal. Clinical real-time tumour motion monitoring with COSMIK was performed offline for 14 liver SBRT patients (41 fractions) and online for one patient (two fractions). The mean 3D root-mean-square error for the four monitoring methods was 1.61 mm (COSMIK), 2.31 mm (ECM without updates), 1.49 mm (ECM with stereoscopic updates) and 0.75 mm (KIM). COSMIK is the first combined kV/optical real-time motion monitoring method used clinically online on a conventional accelerator. COSMIK gives less imaging dose than KIM and is in addition applicable when the kV imager cannot be deployed such as during non-coplanar fields.

Pancreatic gross tumor volume contouring on computed tomography (CT) compared with magnetic resonance imaging (MRI): Results of an international contouring conference

PURPOSE

Accurate identification of the gross tumor volume (GTV) in pancreatic adenocarcinoma is challenging. We sought to understand differences in GTV delineation using pancreatic computed tomography (CT) compared with magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Twelve attending radiation oncologists were convened for an international contouring symposium. All participants had a clinical and research interest in pancreatic adenocarcinoma. CT and MRI scans from 3 pancreatic cases were used for contouring. CT and MRI GTVs were analyzed and compared. Interobserver variability was compared using Dice's similarity coefficient (DSC), Hausdorff distances, and Jaccard indices. Mann-Whitney tests were used to check for significant differences. Consensus contours on CT and MRI scans and constructed count maps were used to visualize the agreement. Agreement regarding the optimal method to determine GTV definition using MRI was reached.

RESULTS

Six contour sets (3 from CT and 3 from MRI) were obtained and compared for each observer, totaling 72 contour sets. The mean volume of contours on CT was significantly larger at 57.48 mL compared with a mean of 45.76 mL on MRI, P = .011. The standard deviation obtained from the CT contours was significantly larger than the standard deviation from the MRI contours (P = .027). The mean DSC was 0.73 for the CT and 0.72 for the MRI (P = .889). The conformity index measurement was similar for CT and MRI (P = .58). Count maps were created to highlight differences in the contours from CT and MRI.

CONCLUSIONS

Using MRI as a primary image set to define a pancreatic adenocarcinoma GTV resulted in smaller contours compared with CT. No differences in DSC or the conformity index were seen between MRI and CT. A stepwise method is recommended as an approach to contour a pancreatic GTV using MRI.

Outcomes and toxicity following Yttrium-90 radioembolization for hepatic metastases from neuroendocrine tumors-a single-institution experience

Background

The prognosis of patients with hepatic metastases from neuroendocrine tumors (NET) is generally good, and radioembolization with Yttrium-90 microspheres is a locoregional therapy that is used in efforts to improve hepatic disease control and survival. This study aims to describe the survival outcomes and toxicities associated with radioembolization for hepatic-predominant metastatic NET in a large single-institution cohort.

Methods

A total of 59 patients underwent radioembolization for metastatic NET with hepatic predominant disease at a single academic center. Patient outcomes were analyzed by Kaplan-Meier survival analysis and toxicities were detailed and described. Ten patients within the cohort underwent post-treatment dosimetric analysis using PET-MRI and normal liver dosimetry was correlated with hepatic fibrosis and toxicity.

Results

Median overall survival from time of radioembolization in the patient cohort was 31 months, and the 1- and 2-year overall survival was 80.4% and 65.6% respectively. Median hepatic progression-free survival and overall progression-free survival were 18 and 13 months, respectively. Three patients died of hepatic failure that was possibly therapy-related. Ten patients underwent evaluation of post-treatment dosimetry following radioembolization. In patients who did not develop hepatotoxicity or hepatic fibrosis, mean dose to normal liver was 25.4 Gy, while the mean liver dose in patients who experienced toxicity (hepatic fibrosis in n=2 and death from hepatic failure in n=1) was 59.1 Gy.

Conclusions

Overall survival following radioembolization for hepatic metastases from NET is excellent; however, deaths that are potentially treatment-related have been observed. Preliminary data regarding dose to normal liver is suggestive of a relation between dosimetry and toxicity, however further work is required to further elucidate the mechanism, correlation with dosimetry, as well as additional patient and tumor factors that may predispose these patients to toxicity.

Treatment utilization and outcomes in elderly patients with locally advanced esophageal carcinoma: a review of the National Cancer Database

For elderly patients with locally advanced esophageal cancer, therapeutic approaches and outcomes in a modern cohort are not well characterized. Patients ≥70 years old with clinical stage II and III esophageal cancer diagnosed between 1998 and 2012 were identified from the National Cancer Database and stratified based on treatment type. Variables associated with treatment utilization were evaluated using logistic regression and survival evaluated using Cox proportional hazards analysis. Propensity matching (1:1) was performed to help account for selection bias. A total of 21,593 patients were identified. Median and maximum ages were 77 and 90, respectively. Treatment included palliative therapy (24.3%), chemoradiation (37.1%), trimodality therapy (10.0%), esophagectomy alone (5.6%), or no therapy (12.9%). Age ≥80 (OR 0.73), female gender (OR 0.81), Charlson-Deyo comorbidity score ≥2 (OR 0.82), and high-volume centers (OR 0.83) were associated with a decreased likelihood of palliative therapy versus no treatment. Age ≥80 (OR 0.79) and Clinical Stage III (OR 0.33) were associated with a decreased likelihood, while adenocarcinoma histology (OR 1.33) and nonacademic cancer centers (OR 3.9), an increased likelihood of esophagectomy alone compared to definitive chemoradiation. Age ≥80 (OR 0.15), female gender (OR 0.80), and non-Caucasian race (OR 0.63) were associated with a decreased likelihood, while adenocarcinoma histology (OR 2.10) and high-volume centers (OR 2.34), an increased likelihood of trimodality therapy compared to definitive chemoradiation. Each treatment type demonstrated improved survival compared to no therapy: palliative treatment (HR 0.49) to trimodality therapy (HR 0.25) with significance between all groups. Any therapy, including palliative care, was associated with improved survival; however, subsets of elderly patients with locally advanced esophageal cancer are less likely to receive aggressive therapy. Care should be taken to not unnecessarily deprive these individuals of treatment that may improve survival.

Quantitative FDG-PET/CT predicts local recurrence and survival for squamous cell carcinoma of the anus

PURPOSE

18F-fluorodeoxyglucose (FDG) positron emission tomography-(PET)/computed tomography (CT) imaging is used for staging and treatment planning of patients with anal cancer. Quantitative pre- and posttreatment metrics that are predictive of recurrence are unknown. We evaluated the association between pre- and posttreatment FDG-PET/CT parameters and outcomes for patients with squamous cell carcinoma of the anus (SCCA).

METHODS AND MATERIALS

The records of 110 patients treated between 2003 and 2013 with definitive radiation therapy for SCCA were reviewed under an institutional review board-approved protocol. The median radiation therapy dose was 50.4 Gy (range, 35-60 Gy). Concurrent chemotherapy was administered for 109 of 110 patients and generally consisted of 5-fluorouracil and mitomycin C (n = 94). All patients underwent pretreatment FDG-PET/CT and 101 of 110 underwent posttreatment FDG-PET/CT 3 months after completion of radiation therapy. The maximum standard uptake value (SUVmax) was analyzed, in addition to multiple patient and treatment factors, by univariate and multivariate Cox regression for correlation with local recurrence (LR) and overall survival (OS).

RESULTS

The median follow-up was 28.6 months. LR occurred in 1 of 15 (6.7%), 5 of 47 (10.6%), and 6 of 48 (12.5%) patients with stage I, II, and III disease, respectively. On univariate analysis, a significant association was observed between reduced LR and posttreatment SUVmax <6.1 (P = .0095) and between increased OS and posttreatment SUVmax <6.1 (P = .0086). On multivariate analysis, a significant association was observed between reduced LR and posttreatment SUVmax <6.1 (P = .0013) and the use of intensity modulated radiation therapy (P < .001). A significant multivariate association was observed between increased OS and posttreatment SUVmax <6.1 (P = .0373) and the use of 5-fluorouracil/mitomycin C chemotherapy (P = .001).

CONCLUSION

Posttreatment SUVmax <6.1 is associated with reduced LR and increased OS after chemoradiation therapy for SCCA independent of T and N stage on multivariate analysis. Greater follow-up is required to confirm this association with late patterns of failure.

Improved Metastasis- and Disease-Free Survival With Preoperative Sequential Short-Course Radiation Therapy and FOLFOX Chemotherapy for Rectal Cancer Compared With Neoadjuvant Long-Course Chemoradiotherapy: Results of a Matched Pair Analysis

PURPOSE

To compare treatment and toxicity outcomes between a phase 2 institutional trial of near total neoadjuvant therapy (nTNT) for locally advanced rectal cancer and a similar historical control cohort treated at Washington University in St. Louis with the current US standard of care, defined as neoadjuvant chemoradiotherapy (NCRT), total mesorectal excision (TME), and adjuvant FOLFOX chemotherapy; to expand the comparison to an additional institution, patients treated with similar NCRT at Stanford University were included.

METHODS AND MATERIALS

Sixty-nine patients with cT3-4N0-2M0 rectal adenocarcinoma enrolled on the Washington University in St. Louis phase 2 study of nTNT were included for analysis. Patients treated at the same institution with conventional NCRT and adjuvant FOLFOX were matched for exact cTNM stage. Forty-one patients treated with NCRT at Stanford University were included in a second analysis. Kaplan-Meier analysis with log-rank test was used to compare local control, distant metastasis-free survival, disease-free survival, and overall survival.

RESULTS

Median follow-up was 49 and 54 months for nTNT and NCRT, respectively. Pathologic complete response and T-downstaging rates were 28% versus 16% (P=.21) and 75% versus 41% (P<.001) in the nTNT and NCRT cohorts, respectively. Three-year disease-free survival (85% vs 68%, P=.032) was significantly better in the nTNT group. Actuarial 3-year local control (92% vs 96%, P=.36) and overall survival (96% vs 88%, P=.67) were similar. The Stanford cohort had significantly lower clinical stage. After controlling for clinical stage, age, tumor location, institution, and number of chemotherapy cycles, nTNT treatment remained significantly associated with lower risk of recurrence (P=.006).

CONCLUSIONS

Patients treated with nTNT had higher T-downstaging and superior distant metastasis-free survival and disease-free survival compared with conventional NCRT when matched for tumor location and exact cTNM stage. Near total neoadjuvant therapy remained a significant multivariate predictor for improved outcome when including patients treated with NCRT at another institution.

Utility of a multidisciplinary tumor board in the management of pancreatic and upper gastrointestinal diseases: an observational study

BACKGROUND & OBJECTIVES

Multidisciplinary tumor boards (MDTBs) are frequently employed in cancer centers but their value has been debated. We reviewed the decision-making process and resource utilization of our MDTB to assess its utility in the management of pancreatic and upper gastrointestinal tract conditions.

METHODS

A prospectively-collected database was reviewed over a 12-month period. The primary outcome was change in management plan as a result of case discussion. Secondary outcomes included resources required to hold MDTB, survival, and adherence to treatment guidelines.

RESULTS

Four hundred seventy cases were reviewed. MDTB resulted in a change in the proposed plan of management in 101 of 402 evaluable cases (25.1%). New plans favored obtaining additional diagnostic workup. No recorded variables were associated with a change in plan. For newly-diagnosed cases of pancreatic ductal adenocarcinoma (n = 33), survival time was not impacted by MDTB (p = .154) and adherence to National Comprehensive Cancer Network guidelines was 100%. The estimated cost of physician time per case reviewed was $190.

CONCLUSIONS

Our MDTB influences treatment decisions in a sizeable number of cases with excellent adherence to national guidelines. However, this requires significant time expenditure and may not impact outcomes. Regular assessments of the effectiveness of MDTBs should be undertaken.

A National Cancer Database analysis of treatment utilization and associated outcomes in elderly patients with locally advanced esophageal cancer

138

Background: Elderly patients with locally advanced esophageal cancer pose a therapeutic challenge since definitive treatment involves aggressive combined-modality therapy. Whether these individuals are offered or benefit from these approaches in the modern, trimodality era has not been widely explored. Methods: Patients ≥ 70 years old with clinical stage II and III esophageal cancer diagnosed between 1998 and 2012 were identified from the National Cancer Database and stratified based on treatment. Variables independently associated with treatment utilization were evaluated using logistic regression and mortality hazard evaluated using Cox-proportional hazards analysis. The primary aim was to compare overall survival by treatment group. The secondary aim was to identify variables associated with receiving each modality. Results: A total of 21,593 patients were identified. Median and maximum ages were 77 and 90 respectively. In 12.9%, no therapy was delivered, 24.3% received palliative therapy, 37.1% received definitive chemoradiation, 5.6% received esophagectomy alone, and 10.0% received trimodality therapy. On multivariate analysis, age ≥ 80 (OR 0.73, p < 0.001), female gender (OR 0.81, p < 0.001), and treatment at high-volume centers (OR 0.83, p = 0.008) were associated with a decreased likelihood of palliative therapy over no treatment. Age ≥ 80 (OR 0.15, p < 0.001), female gender (OR 0.80, p = 0.03), and non-Caucasian race (OR 0.63, p < 0.001) were associated with decreased trimodality use compared to definitive chemoradiation. Each treatment independently demonstrated improved survival compared to no therapy: palliative treatment (HR 0.49), concurrent chemoradiation (HR 0.36), esophagectomy (HR 0.31), trimodality therapy (HR 0.25), all p < 0.001. Conclusions: Any therapy, including palliative care, was associated with improved survival compared to no treatment in elderly patients with esophageal cancer. Subsets of patients are less likely to receive aggressive therapy based on social and institutional factors. Care should be taken to not unnecessarily deprive elderly patients of treatment that may improve survival.

Process improvement for the safe delivery of multidisciplinary-executed treatments-A case in Y-90 microspheres therapy

PURPOSE

To develop a safe and robust workflow for yttrium-90 (Y-90) radioembolization procedures in a multidisciplinary team environment.

METHODS AND MATERIALS

A generalized Define-Measure-Analyze-Improve-Control (DMAIC)-based approach to process improvement was applied to a Y-90 radioembolization workflow. In the first DMAIC cycle, events with the Y-90 workflow were defined and analyzed. To improve the workflow, a web-based interactive electronic white board (EWB) system was adopted as the central communication platform and information processing hub. The EWB-based Y-90 workflow then underwent a second DMAIC cycle. Out of 245 treatments, three misses that went undetected until treatment initiation were recorded over a period of 21 months, and root-cause-analysis was performed to determine causes of each incident and opportunities for improvement. The EWB-based Y-90 process was further improved via new rules to define reliable sources of information as inputs into the planning process, as well as new check points to ensure this information was communicated correctly throughout the process flow.

RESULTS

After implementation of the revised EWB-based Y-90 workflow, after two DMAIC-like cycles, there were zero misses out of 153 patient treatments in 1 year.

CONCLUSIONS

The DMAIC-based approach adopted here allowed the iterative development of a robust workflow to achieve an adaptable, event-minimizing planning process despite a complex setting which requires the participation of multiple teams for Y-90 microspheres therapy. Implementation of such a workflow using the EWB or similar platform with a DMAIC-based process improvement approach could be expanded to other treatment procedures, especially those requiring multidisciplinary management.

Preoperative short-course radiation therapy for rectal cancer provides excellent disease control and toxicity: Results from a single US institution

PURPOSE

Preoperative short-course radiation therapy (SCRT) has rarely been used for rectal cancer in the United States, although 2 randomized phase 3 trials demonstrate equivalence to conventional chemoradiation (CRT), and recent updates to national guidelines include this regimen as a treatment option. We sought to evaluate the efficacy and safety of preoperative SCRT followed by immediate surgery within 1 week to treat rectal cancer in the US setting.

METHODS AND MATERIALS

All patients treated with preoperative SCRT (4 Gy × 5 fractions for total 20 Gy) followed by planned surgery within 1 week at our institution were retrospectively evaluated. Censored cases with ≥2 years of follow-up were included along with any disease failure or death. Patients with cM1 disease were excluded. Patients with yp stage II/III disease typically received adjuvant chemotherapy from the 1990s onwards. The primary outcomes were actuarial (Kaplan-Meier) 5-year locoregional control (LC), disease-free survival (DFS), and overall survival (OS) as well as late severe (greater than or equal to grade 3) toxicity.

RESULTS

Our analysis included 202 consecutive patients with clinical stage I-III disease treated from 1977 through 2011. Median follow-up was 6.5 years (range, 2-29.2). Five-year disease outcomes were 95.9% ± 1.5% for LC, 76.4% ± 3.1% for DFS, and 84.6% ± 2.6% for OS. For patients with locally advanced rectal cancer (cT3-4 and/or cN+), 5-year LC, DFS, and OS were 95.1% ± 2.1%, 73.3% ± 4.3%, and 80.6% ± 3.7%, respectively. The late severe toxicity rate was 11.4%.

CONCLUSIONS

SCRT followed by immediate surgery is a safe and effective treatment for patients with rectal cancer in the United States. Though SCRT has not been widely adopted, recent updates to the national guidelines for rectal cancer as well as financial pressures to reduce healthcare costs may lead to increased utilization of this treatment regimen in the future.

A comparative study of automatic image segmentation algorithms for target tracking in MR-IGRT

On-board magnetic resonance (MR) image guidance during radiation therapy offers the potential for more accurate treatment delivery. To utilize the real-time image information, a crucial prerequisite is the ability to successfully segment and track regions of interest (ROI). The purpose of this work is to evaluate the performance of different segmentation algorithms using motion images (4 frames per second) acquired using a MR image-guided radiotherapy (MR-IGRT) system. Manual con-tours of the kidney, bladder, duodenum, and a liver tumor by an experienced radiation oncologist were used as the ground truth for performance evaluation. Besides the manual segmentation, images were automatically segmented using thresholding, fuzzy k-means (FKM), k-harmonic means (KHM), and reaction-diffusion level set evolution (RD-LSE) algorithms, as well as the tissue tracking algorithm provided by the ViewRay treatment planning and delivery system (VR-TPDS). The performance of the five algorithms was evaluated quantitatively by comparing with the manual segmentation using the Dice coefficient and target registration error (TRE) measured as the distance between the centroid of the manual ROI and the centroid of the automatically segmented ROI. All methods were able to successfully segment the bladder and the kidney, but only FKM, KHM, and VR-TPDS were able to segment the liver tumor and the duodenum. The performance of the thresholding, FKM, KHM, and RD-LSE algorithms degraded as the local image contrast decreased, whereas the performance of the VP-TPDS method was nearly independent of local image contrast due to the reference registration algorithm. For segmenting high-contrast images (i.e., kidney), the thresholding method provided the best speed (< 1 ms) with a satisfying accuracy (Dice = 0.95). When the image contrast was low, the VR-TPDS method had the best automatic contour. Results suggest an image quality determination procedure before segmentation and a combination of different methods for optimal segmentation with the on-board MR-IGRT system.

Prospective phase I study of nab-paclitaxel plus gemcitabine with concurrent MR-guided IMRT in patients with locally advanced or borderline resectable pancreatic cancer

TPS480

Background: Radiotherapy (RT) for locally advanced and borderline resectable pancreatic cancer (LABPC) is controversial as potential local control benefits are often obscured by high rates of distant progression. However, local failure remains a significant cause of morbidity among patients without distant progression after initial chemotherapy, although toxicity concerns may limit delivery of optimal systemic therapy concurrent with RT. Given known systemic efficacy and radiosensitization effects of nab-paclitaxel (A) with gemcitabine (G), we initiated a phase I study of nab-paclitaxel with gemcitabine (AG) and concurrent intensity modulated radiation therapy with magnetic resonance guidance (MR-IMRT) for LABPC. Methods: A planned 24 patients with LABPC will be enrolled to a phase I dose escalation trial using the Time-to-Event Continual Reassessment Method (TITE-CRM) design. Following one lead-in cycle of GA, MR-IMRT is administered daily with concurrent weekly GA for a total of 25 fractions in 5 weeks. The initial dose levels for RT and AG, respectively, are: 40 Gy MR-IMRT, 75 mg/m2 A and 600mg/m2 G. The maximum possible dose level is 60 Gy MR-IMRT, 100mg/m2 A and 1000mg/m2 G. To reduce toxicity risk, MR-IMRT volumes include the primary tumor only, with cine-MR used for intra-fraction tumor tracking in place of fiducial markers. The primary endpoint is determination of the maximum tolerated dose level, with secondary endpoints including rate of conversion to resectable disease, progression- free survival, overall survival, and patient reported quality of life. Clinical trial information: NCT02283372.

Utility of a multidisciplinary tumor board in the management of pancreatic diseases

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Background: Multidisciplinary Tumor Boards (MTBs) are a requirement for comprehensive cancer centers and are routinely used to coordinate multidisciplinary care in oncology. Despite their widespread use, the impact of MTBs is not well characterized. We studied the outcomes of all patients presented at our pancreas MTB, with the goal of evaluating our current practices and resource utilization. Methods: Data were prospectively collected for all patients presented at a weekly pancreas-specific MTB over the 12-month period at a single-institution NCI-designated cancer center. The conference is attended by surgical, medical, and radiation oncologists, interventional gastroenterologists, pathologists, and radiologists (diagnostic and interventional). Retrospective chart review was performed at the end of the 12-month period under an IRB-approved protocol. Results: A total of 470 patient presentations were made over a 12-month period. Average age at time of presentation was 61.5 years (range 17 – 89) with 51% males. 61.7% of cases were presented by surgical oncologists and 26% by medical oncologists. 174 cases were the result of new diagnoses or referrals. 78 patients were presented more than once (average of 2.3 times). Pancreatic adenocarcinoma was the most common diagnosis (37%), followed by uncharacterized pancreatic mass (16%), and pancreatic cyst (7%). The treatment plan proposed by the presenting clinician was known or could be evaluated prior to conference in 402 cases. Presentation of a case at MTB changed the plan of management 25% (n = 100) of the time, including MTB recommendation against a planned resection in 46 cases. When the initial plan changed as a result of MTB discussion, the most common new plan was to obtain further diagnostic testing such as biopsy and/or endoscopy (n = 24). Conclusions: MTBs are required and resource-intensive but offer the opportunity to discuss a wide array of pathologies and influence management decisions in a sizable proportion of cases. Additional investigations evaluating adherence rates to MTB decisions and to published guidelines (i.e. National Comprehensive Cancer Network) will further enhance the assessment and utility of MTBs.

Process-based quality management for clinical implementation of adaptive radiotherapy

PURPOSE

Intensity-modulated adaptive radiotherapy (ART) has been the focus of considerable research and developmental work due to its potential therapeutic benefits. However, in light of its unique quality assurance (QA) challenges, no one has described a robust framework for its clinical implementation. In fact, recent position papers by ASTRO and AAPM have firmly endorsed pretreatment patient-specific IMRT QA, which limits the feasibility of online ART. The authors aim to address these obstacles by applying failure mode and effects analysis (FMEA) to identify high-priority errors and appropriate risk-mitigation strategies for clinical implementation of intensity-modulated ART.

METHODS

An experienced team of two clinical medical physicists, one clinical engineer, and one radiation oncologist was assembled to perform a standard FMEA for intensity-modulated ART. A set of 216 potential radiotherapy failures composed by the forthcoming AAPM task group 100 (TG-100) was used as the basis. Of the 216 failures, 127 were identified as most relevant to an ART scheme. Using the associated TG-100 FMEA values as a baseline, the team considered how the likeliness of occurrence (O), outcome severity (S), and likeliness of failure being undetected (D) would change for ART. New risk priority numbers (RPN) were calculated. Failures characterized by RPN ≥ 200 were identified as potentially critical.

RESULTS

FMEA revealed that ART RPN increased for 38% (n = 48/127) of potential failures, with 75% (n = 36/48) attributed to failures in the segmentation and treatment planning processes. Forty-three of 127 failures were identified as potentially critical. Risk-mitigation strategies include implementing a suite of quality control and decision support software, specialty QA software/hardware tools, and an increase in specially trained personnel.

CONCLUSIONS

Results of the FMEA-based risk assessment demonstrate that intensity-modulated ART introduces different (but not necessarily more) risks than standard IMRT and may be safely implemented with the proper mitigations.

Comparison of onboard low-field magnetic resonance imaging versus onboard computed tomography for anatomy visualization in radiotherapy

BACKGROUND

Onboard magnetic resonance imaging (OB-MRI) for daily localization and adaptive radiotherapy has been under development by several groups. However, no clinical studies have evaluated whether OB-MRI improves visualization of the target and organs at risk (OARs) compared to standard onboard computed tomography (OB-CT). This study compared visualization of patient anatomy on images acquired on the MRI-(60)Co ViewRay system to those acquired with OB-CT.

MATERIAL AND METHODS

Fourteen patients enrolled on a protocol approved by the Institutional Review Board (IRB) and undergoing image-guided radiotherapy for cancer in the thorax (n = 2), pelvis (n = 6), abdomen (n = 3) or head and neck (n = 3) were imaged with OB-MRI and OB-CT. For each of the 14 patients, the OB-MRI and OB-CT datasets were displayed side-by-side and independently reviewed by three radiation oncologists. Each physician was asked to evaluate which dataset offered better visualization of the target and OARs. A quantitative contouring study was performed on two abdominal patients to assess if OB-MRI could offer improved inter-observer segmentation agreement for adaptive planning.

RESULTS

In total 221 OARs and 10 targets were compared for visualization on OB-MRI and OB-CT by each of the three physicians. The majority of physicians (two or more) evaluated visualization on MRI as better for 71% of structures, worse for 10% of structures, and equivalent for 14% of structures. 5% of structures were not visible on either. Physicians agreed unanimously for 74% and in majority for > 99% of structures. Targets were better visualized on MRI in 4/10 cases, and never on OB-CT.

CONCLUSION

Low-field MR provides better anatomic visualization of many radiotherapy targets and most OARs as compared to OB-CT. Further studies with OB-MRI should be pursued.

Pretreatment diffusion weighted imaging for clinical outcome assessment in patients undergoing definitive chemoradiation for pancreatic adenocarcinoma

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Background: Factors predicting patterns of failure for pancreatic ductal adenocarcinoma (PDA) are not well-established. Diffusion-weighted MRI (DWI) is useful in predicting recurrence for other gastrointestinal malignancies. The purpose of this study was to evaluate for correlation between tumor DWI parameters and clinical outcomes following chemoradiotherapy (CRT) for pancreatic adenocarcinoma. Methods: From 2009 to 2013, 27 patients with locally advanced (n=14), borderline resectable (n=12) or resectable (n=1) PDA underwent CRT. All patients received upfront FOLFIRINOX or gemcitabine-based chemotherapy prior to CRT, and gemcitabine (median weekly dose 800 mg/m2) concurrent with radiotherapy. DWI was obtained during radiotherapy treatment planning, and apparent diffusion coefficient (ADC) maps were generated to allow determination of median tumor ADC. Tumor-directed CRT was administered with respiratory gated intensity modulated radiation therapy, 55Gy in 25 fractions without elective nodal coverage. Patients were followed by imaging every 2-3 months. Log rank test was used to estimate an optimal ADC cut-point of 1.4*10-3mm2/sec based on distant metastasis free survival (DMFS) and overall survival (OS). Analysis of local recurrence was not performed due to limited events. The log-rank test was used to evaluate differences in outcome between groups based on ADC classification. Results: The median time to last follow-up from completion of CRT was 9.7 months for all patients and 11 months among living patients. 5 patients underwent resection following CRT. The 1-year DMFS for patients with median ADC<1.4*10-3mm2/sec was 79.5 percent, compared to 47.6 percent for those with median ADC >1.4. The 1-year OS for patients with median ADC<1.4 was 100 percent, compared to 46.3 percent for those with median ADC >1.4. Both DMFS (p=.041) and OS (p=.003) were significantly improved on log-rank test for ADC<1.4 compared to ADC>1.4. Conclusions: A correlation was observed between DWI parameters and clinical outcomes for PDA. Further prospective study should be explored to validate DWI as a prognostic imaging biomarker.

Matched pair analysis of sequential short course radiotherapy and FOLFOX chemotherapy as preoperative therapy for rectal cancer compared to neoadjuvant long course chemoradiotherapy

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Background: A recently completed institutional phase II trial evaluated near-total neoadjuvant therapy (nTNT) for locally advanced rectal cancer using short course radiotherapy (SCRT) followed by four cycles of FOLFOX prior to total mesorectal excision (TME). A matched pair analysis is presented to compare clinical outcomes for nTNT with conventional chemoradiotherapy (CRT), TME, and postoperative chemotherapy (CT) for patients treated at our institution. Methods: 80 patients with cT3-4N0-2M0-1 rectal adenocarcinoma planned for resection of all tumor enrolled on a phase II study of preoperative SCRT (25 Gy to the involved mesorectum, 20 Gy to elective nodes, in 5 fractions) followed by four cycles of mFOLFOX6 before TME, with 6-8 cycles of adjuvant FOLFOX suggested. 69 patients with cM0 disease comprised the study cohort for this analysis. Patients treated with conventional CRT, followed by TME and adjuvant CT (63% ≥4 cycles adjuvant FOLFOX) were identified and matched 2:1 for exact cTNM stage. Kaplan-Meier with log-rank analysis was used to compare local control (LC), distant metastasis free survival (DMFS), disease free survival (DFS), and overall survival (OS), and two-tailed Mann-Whitney and Chi-squared tests used to compare cohort characteristics. Results: Median follow-up was 26 and 49 months for the study and control groups, respectively. Median age (57 vs. 55 years, p = 0.98) and distance from the anorectal ring (6 vs. 5 cm, p = 0.16) were similar for study and control groups, respectively. Pathologic complete response (pCR) and T-downstaging rates were 30% vs. 23% (p = 0.26) and 75% vs 50% (p = 0.001) in the study and match cohort, respectively. Actuarial 2-year LC (97% vs. 98%, p = 0.69) and OS (100% vs. 95% at 2 years, p = 0.57) were similar between the study and control groups, respectively. Two-year DMFS (94% vs. 80%, p = 0.016) and DFS (94% vs. 80%, p = 0.027) were significantly better in the study cohort. Conclusions: Controlling for institutional bias, exact cTNM stage, and tumor location, nTNT resulted in increased T-downstaging, superior DMFS and DFS, and similar LC and OS compared to conventional CRT.