Designing clinical trials for patients who are not average

The heterogeneity inherent in cancer means that even a successful clinical trial merely results in a therapeutic regimen that achieves, on average, a positive result only in a subset of patients. The only way to optimize an intervention for an individual patient is to reframe their treatment as their own, personalized trial. Toward this goal, we formulate a computational framework for performing personalized trials that rely on four mathematical techniques. First, mathematical models that can be calibrated with patient-specific data to make accurate predictions of response. Second, digital twins built on these models capable of simulating the effects of interventions. Third, optimal control theory applied to the digital twins to optimize outcomes. Fourth, data assimilation to continually update and refine predictions in response to therapeutic interventions. In this perspective, we describe each of these techniques, quantify their "state of readiness", and identify use cases for personalized clinical trials.

Management and long-term clinical outcomes of patients with stage IVA cervical cancer with bladder involvement

OBJECTIVE

To describe the long-term outcomes of patients with stage IVA cervical cancer, a rare and deadly disease for which long-term toxicity data are scarce, to guide clinician counseling and survivorship support.

METHODS

In a retrospective review of a prospectively maintained database, we identified 76 patients with stage IVA cervical cancer with biopsy- or MRI-proven bladder mucosal involvement who received definitive radiotherapy (external beam radiotherapy [EBRT] alone or EBRT plus brachytherapy) with or without chemotherapy at our institution between 2000 and 2020. We used Kaplan-Meier modeling to estimate recurrence-free survival (RFS) and overall survival (OS) and used proportional hazard modeling to identify clinical variables associated with recurrence or survival. We performed actuarial competing risk modeling for severe late toxicity (grades 3 to 5, occurring >6 months of follow-up) and vesicovaginal fistulae (VVF), censoring for pelvic recurrence and death, and made comparisons between potential predictors using Gray's test and binary logistic regression.

RESULTS

The median follow-up time was 76 months (interquartile range 58-91). The median OS duration was 35 months (range, 18-not reached), and the 2- and 5-year OS rates were 53.6% and 40.9%, respectively. OS and RFS did not differ significantly between patients who received EBRT alone (N = 18) or EBRT plus brachytherapy (N = 49). Current smoking was a strong predictor of severe late toxicity, whose incidence was 14% at 2 years and 17% at 10 years. The VVF incidence was 24% at 2 years and 32% at 10 years.

CONCLUSION

Patients with stage IVA cervical cancer, even those who receive EBRT alone, can have long-term survival. These patients should be followed closely for late radiation-related toxicity.

Feasibility of quantitative diffusion-weighted imaging during intra-procedural MRI-guided brachytherapy of locally advanced cervical and vaginal cancers

PURPOSE

To determine the feasibility of quantitative apparent diffusion coefficient (ADC) acquisition during magnetic resonance imaging-guided brachytherapy (MRgBT) using reduced field-of-view (rFOV) diffusion-weighted imaging (DWI).

METHODS AND MATERIALS

T2-weighted (T2w) MR and full-FOV single-shot echo planar (ssEPI) DWI were acquired in 7 patients with cervical or vaginal malignancy at baseline and prior to brachytherapy, while rFOV-DWI was acquired during MRgBT following brachytherapy applicator placement. The gross target volume (GTV) was contoured on the T2w images and registered to the ADC map. Voxels at the GTV's maximum Maurer distance comprised a central sub-volume (GTVcenter). Contour ADC mean and standard deviation were compared between timepoints using repeated measures ANOVA.

RESULTS

ssEPI-DWI mean ADC increased between baseline and prebrachytherapy from 1.03 ± 0.18 10-3 mm2/s to 1.34 ± 0.28 10-3 mm2/s for the GTV (p = 0.06) and from 0.84 ± 0.13 10-3 mm2/s to 1.26 ± 0.25 10-3 mm2/s at the level of the GTVcenter (p = 0.03), consistent with early treatment response. rFOV-DWI during MRgBT demonstrated mean ADC values of 1.28 ± 0.14 10-3 mm2/s and 1.28 ± 0.19 10-3 mm2/s for the GTV and GTVcenter, respectively (p = 0.02 and p = 0.03 relative to baseline). No significant differences were observed between ssEPI-DWI and rFOV-DWI ADC measurements.

CONCLUSIONS

Quantitative ADC measurement in the setting of MRI guided brachytherapy implant placement for cervical and vaginal cancers is feasible using rFOV-DWI, with comparable mean ADC comparable to prebrachytherapy ssEPI-DWI, and may enable MRI-guided radiotherapy targeting of low ADC, radiation resistant sub-volumes of tumor.

Operational Ontology for Oncology (O3): A Professional Society-Based, Multistakeholder, Consensus-Driven Informatics Standard Supporting Clinical and Research Use of Real-World Data From Patients Treated for Cancer

PURPOSE

The ongoing lack of data standardization severely undermines the potential for automated learning from the vast amount of information routinely archived in electronic health records (EHRs), radiation oncology information systems, treatment planning systems, and other cancer care and outcomes databases. We sought to create a standardized ontology for clinical data, social determinants of health, and other radiation oncology concepts and interrelationships.

METHODS AND MATERIALS

The American Association of Physicists in Medicine's Big Data Science Committee was initiated in July 2019 to explore common ground from the stakeholders' collective experience of issues that typically compromise the formation of large inter- and intra-institutional databases from EHRs. The Big Data Science Committee adopted an iterative, cyclical approach to engaging stakeholders beyond its membership to optimize the integration of diverse perspectives from the community.

RESULTS

We developed the Operational Ontology for Oncology (O3), which identified 42 key elements, 359 attributes, 144 value sets, and 155 relationships ranked in relative importance of clinical significance, likelihood of availability in EHRs, and the ability to modify routine clinical processes to permit aggregation. Recommendations are provided for best use and development of the O3 to 4 constituencies: device manufacturers, centers of clinical care, researchers, and professional societies.

CONCLUSIONS

O3 is designed to extend and interoperate with existing global infrastructure and data science standards. The implementation of these recommendations will lower the barriers for aggregation of information that could be used to create large, representative, findable, accessible, interoperable, and reusable data sets to support the scientific objectives of grant programs. The construction of comprehensive "real-world" data sets and application of advanced analytical techniques, including artificial intelligence, holds the potential to revolutionize patient management and improve outcomes by leveraging increased access to information derived from larger, more representative data sets.

Uncertainty in magnetic resonance imaging-based prostate postimplant dosimetry: Results of a 10-person human observer study, and comparisons with automatic postimplant dosimetry

PURPOSE

Uncertainties in postimplant quality assessment (QA) for low-dose-rate prostate brachytherapy (LDRPBT) are introduced at two steps: seed localization and contouring. We quantified how interobserver variability (IoV) introduced in both steps impacts dose-volume-histogram (DVH) parameters for MRI-based LDRPBT, and compared it with automatically derived DVH parameters.

METHODS AND MATERIALS

Twenty-five patients received MRI-based LDRPBT. Seven clinical observers contoured the prostate and four organs at risk, and 4 dosimetrists performed seed localization, on each MRI. Twenty-eight unique manual postimplant QAs were created for each patient from unique observer pairs. Reference QA and automatic QA were also performed for each patient. IoV of prostate, rectum, and external urinary sphincter (EUS) DVH parameters owing to seed localization and contouring was quantified with coefficients of variation. Automatically derived DVH parameters were compared with those of the reference plans.

RESULTS

Coefficients of variation (CoVs) owing to contouring variability (CoVcontours) were significantly higher than those due to seed localization variability (CoVseeds) (median CoVcontours vs. median CoVseeds: prostate D90-15.12% vs. 0.65%, p < 0.001; prostate V100-5.36% vs. 0.37%, p < 0.001; rectum V100-79.23% vs. 8.69%, p < 0.001; EUS V200-107.74% vs. 21.18%, p < 0.001). CoVcontours were lower when the contouring observers were restricted to the 3 radiation oncologists, but were still markedly higher than CoVseeds. Median differences in prostate D90, prostate V100, rectum V100, and EUS V200 between automatically computed and reference dosimetry parameters were 3.16%, 1.63%, -0.00 mL, and -0.00 mL, respectively.

CONCLUSIONS

Seed localization introduces substantially less variability in postimplant QA than does contouring for MRI-based LDRPBT. While automatic seed localization may potentially help improve workflow efficiency, it has limited potential for improving the consistency and quality of postimplant dosimetry.

Gynecologic oncology tumor board: the central role of the radiologist

This manuscript is a collaborative, multi-institutional effort by members of the Society of Abdominal Radiology Uterine and Ovarian Cancer Disease Focus Panel and the European Society of Urogenital Radiology Women Pelvic Imaging working group. The manuscript reviews the key role radiologists play at tumor board and highlights key imaging findings that guide management decisions in patients with the most common gynecologic malignancies including ovarian cancer, cervical cancer, and endometrial cancer.

Image Fusion Technology in Interventional Radiology

Image fusion technology aims to improve patient outcomes for image-guided interventions by leveraging the strengths of multimodality imaging datasets. This most commonly involves the overlay or co-display of advanced cross-sectional imaging permitting freedom of device placement via conventional image guidance such as ultrasound, fluoroscopy, and computed tomography. This can allow the interventionalist to target and treat lesions that would otherwise be difficult or impossible to visualize and access using conventional imaging guidance. Furthermore, the use of image fusion can allow for procedures traditionally performed with cross-sectional imaging to be performed under ultrasound or fluoroscopy, by importing the data from preacquired cross-sectional imaging into the interventional procedure. This manuscript provides an overview of image fusion technologies used for interventional radiology (IR) guidance, with an emphasis on technical considerations.

Image-Guided Radiotherapy for Gynecologic Malignancies: What the Radiologist Needs to Know

Pelvic imaging is integral to contemporary radiotherapy (RT) management of gynecologic malignancies. For cervical, endometrial, vulvar, and vaginal cancers, three-dimensional imaging modalities aid in tumor staging and RT candidate selection and inform treatment strategy, including RT planning, execution, and posttherapy surveillance. State-of-the-art care routinely incorporates magnetic resonance (MR) imaging, 18F-fluorodeoxyglucose-PET/computed tomography (CT), and CT to guide external beam RT and brachytherapy, allowing the customization of RT plans to maximize patient outcomes and reduce treatment-related toxicities. Follow-up imaging identifies radiation-resistant and recurrent disease as well as short-term and long-term toxicities from RT.

MR Imaging of Gynecologic Tumors: Pearls, Pitfalls, and Tumor Mimics

MR imaging is the modality of choice for the pre-treatment evaluation of patients with gynecologic malignancies, given its excellent soft tissue contrast and multi-planar capability. However, it is not without pitfalls. Challenges can be encountered in the assessment of the infiltration of myometrium, vagina, cervical stroma, and parametria, which are crucial prognostic factors for endometrial and cervical cancers. Other challenges can be encountered in the distinction between solid and non-solid tissue and in the identification of peritoneal carcinomatosis for the sonographically indeterminate adnexal mass.

ACR Appropriateness Criteria® Post-Treatment Follow-up of Prostate Cancer: 2022 Update

Prostate cancer has a wide spectrum ranging between low-grade localized disease and castrate-resistant metastatic disease. Although whole gland and systematic therapies result in cure in the majority of patients, recurrent and metastatic prostate cancer can still occur. Imaging approaches including anatomic, functional, and molecular modalities are continuously expanding. Currently, recurrent and metastatic prostate cancer is grouped in three major categories: 1) Clinical concern for residual or recurrent disease after radical prostatectomy, 2) Clinical concern for residual or recurrent disease after nonsurgical local and pelvic treatments, and 3) Metastatic prostate cancer treated by systemic therapy (androgen deprivation therapy, chemotherapy, immunotherapy). This document is a review of the current literature regarding imaging in these settings and the resulting recommendations for imaging. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Abstract 850: Patient-specific, organ-scale forecasting of prostate cancer growth in active surveillance

Active surveillance (AS) is an established clinical strategy for the management of prostate cancer (PCa) exhibiting low to intermediate risk. In AS, treatment is delayed until progression to higher-risk disease is detected during the close monitoring of patients via longitudinal multiparametric magnetic resonance imaging (mpMRI) scans, biopsies, and Prostate Specific Antigen (PSA) tests. Thus, AS has been regarded as a promising strategy to address the current rates of overtreatment and undertreatment in PCa. However, current AS protocols rely on an observational paradigm, which may delay the detection of tumor progression, and the testing frequency is largely fixed according to population studies, which impedes the design of personalized monitoring plans. To address these issues, we propose to advance AS towards a predictive patient-specific paradigm by leveraging computational tumor forecasts obtained with a biomechanistic model informed by the imaging and clinical data collected during standard AS for each individual patient.

Here, we present a preliminary study in a cohort of eight PCa patients who enrolled in AS and had three mpMRI scans over a period of 2.6 to 5.6 years. Our model describes PCa growth in terms of the dynamics of tumor cell density as a combination of tumor cell mobility and net proliferation, which are formulated as a diffusion process and logistic growth, respectively. The model is implemented in each patient’s prostate geometry, which is segmented on T2-weighted MRI data. Tumor cell density estimates are derived from Apparent Diffusion Coefficient (ADC) maps obtained from diffusion-weighted MRI data. To facilitate modeling, the longitudinal imaging datasets are non-rigidly co-registered for each patient. We initialize the model with the tumor cell density map obtained from the ADC map of the first mpMRI scan. Then, the model is parameterized by minimizing the model-data mismatch in tumor cell density at the date of a second mpMRI scan. Finally, we perform a tumor forecast up to the date of a third mpMRI scan, which we use to assess the model-data agreement of our predictions of PCa growth.

We obtained a concordance correlation coefficient (CCC) for tumor volume and global tumor cell count of 0.87 and 0.95 during model calibration and of 0.91 and 0.87 at forecasting horizon, respectively. For each patient, the spatial fit of tumor cell density yielded a median Dice score and CCC of 0.77 and 0.50 at the second mpMRI date, respectively. Likewise, the tumor cell density predictions at the third scan date resulted in a median Dice coefficient and CCC of 0.74 and 0.51 across the patient cohort, respectively. Thus, while further model development and performance assessment over lager cohorts are required, these results suggest that our forecasting technology is a promising tool to predict PCa progression in AS and, hence, identify patients who require treatment early during the course of AS.

Citation Format: Guillermo Lorenzo Gomez, Chengyue Wu, Joshua P. Yung, John F. Ward, Hector Gomez, Alessandro Reali, Thomas E. Yankeelov, Aradhana M. Venkatesan, Thomas J. Hughes. Patient-specific, organ-scale forecasting of prostate cancer growth in active surveillance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 850.

Imaging of Endometrial Cancer

Endometrial cancer is the most common gynecologic cancer in the United States and Europe, with an increasing incidence rate in high-income countries. MR imaging is recommended for treatment planning because it provides critical information on the extent of myometrial and cervical invasion, extrauterine spread, and lymph node status, all of which are important in the selection of the most appropriate therapy. This article highlights the added value of imaging, focused on MR imaging, in the assessment of endometrial cancer and summarizes the role of MR imaging for endometrial cancer risk stratification and management.

Phase 1b/2 study of combination 177Lu girentuximab plus cabozantinib and nivolumab in treatment naïve patients with advanced clear cell RCC

TPS749

Background: Complete response (CR) is still a rare event in patients with advanced clear cell renal cell carcinoma (ccRCC). The combination of nivolumab plus cabozantinib was recently approved for the first-line treatment of ccRCC based on the CheckMate 9ER phase 3 study demonstrating improved progression-free survival (PFS) and objective response rate (ORR) in comparison to sunitinib. However, the CR rate was only 9%. Since the anti-tumor effects of immune checkpoint inhibitors are dependent on the presence of activated tumor-infiltrating T cells, drugs that could synergize with T cells’ anti-tumor activity can allow us to improve CR rates. Activation of the cGAS-STING pathway which is induced by radiation-induced DNA damage, is one promising mechanism that has been investigated. Many studies have shown that radiation treatment augments immune checkpoint inhibition. However, it is not always possible to radiate all metastatic lesions. Therefore, targeted peptide receptor radionuclide therapies, have been developed by conjugating radioisotopes to receptor binding analogs targeting specific cancer cell surface proteins, thereby delivering targeted radiation to cancer cells in the body with minimal damage to surrounding healthy cells. 177Lu girentuximab is the first antibody-radioisotope designed for ccRCC, targeting carbonic anhydrase 9-expressing cells, which includes >90% of ccRCC. It has been tested in metastatic ccRCC as a single agent and shown to be safe and effective in stabilizing disease in 57% of pts. In this study, we hypothesize that 177Lu girentuximab-induced DNA damage will potentiate the STING pathway, and this activation will synergize with nivolumab and cabozantinib to promote trafficking and infiltration of activated T cells to tumors and achieve higher CR rates. Methods: Up to 100 patients with treatment naïve, biopsy-proven ccRCC with adequate organ/marrow function with ≥1 evaluable lesion by RECIST 1.1 will be enrolled. A 5-patient safety lead-in will evaluate myelosuppression. Ongoing safety, and futility monitoring will employ a Bayesian approach. The sample size was chosen for reasonable operating characteristics to distinguish a CR rate (primary endpoint) of 18% as better than 9% using a beta(0.09, 0.91) prior. Secondary endpoints are ORR, PFS by RECIST 1.1, and overall survival. 177Lu-girentuximab 1480 MBq/m2 (61% of single agent MTD) will be administered every 12 weeks for up to 3 cycles. Starting with the second cycle, nivolumab and cabozantinib will be added at standard dose. To explore the effects of the treatment on inducing activated T cell infiltration, patients will undergo pre/post-treatment PET scan with [18F]F-AraG radiotracer as well as biopsies for single cell, spatial transcriptomics and proteomics studies. This investigator initiated trial is supported by Telix Pharmaceuticals and DOD grant W81XWH-22-1-0456.

Update on MRI in Evaluation and Treatment of Endometrial Cancer

Endometrial cancer is the second most common gynecologic cancer worldwide and the most common gynecologic cancer in the United States, with an increasing incidence in high-income countries. Although the International Federation of Gynecology and Obstetrics (FIGO) staging system for endometrial cancer is a surgical staging system, contemporary published evidence-based data and expert opinions recommend MRI for treatment planning as it provides critical diagnostic information on tumor size and depth, extent of myometrial and cervical invasion, extrauterine extent, and lymph node status, all of which are essential in choosing the most appropriate therapy. Multiparametric MRI using a combination of T2-weighted sequences, diffusion-weighted imaging, and multiphase contrast-enhanced imaging is the mainstay for imaging assessment of endometrial cancer. Identification of important prognostic factors at MRI improves both treatment selection and posttreatment follow-up. MRI also plays a crucial role for fertility-preserving strategies and in patients who are not surgical candidates by helping guide therapy and identify procedural complications. This review is a product of the Society of Abdominal Radiology Uterine and Ovarian Cancer Disease-Focused Panel and reflects a multidisciplinary international collaborative effort to summarize updated information highlighting the role of MRI for endometrial cancer depiction and delineation, treatment planning, and follow-up. The article includes information regarding dedicated MRI protocols, tips for MRI reporting, imaging pitfalls, and strategies for image quality optimization. The roles of MRI-guided radiation therapy, hybrid PET/MRI, and advanced MRI techniques that are applicable to endometrial cancer imaging are also discussed. Online supplemental material is available for this article. ^©RSNA, 2022.

Contemporary image-guided cervical cancer brachytherapy: Consensus imaging recommendations from the Society of Abdominal Radiology and the American Brachytherapy Society

PURPOSE

To present recommendations for the use of imaging for evaluation and procedural guidance of brachytherapy for cervical cancer patients.

METHODS

An expert panel comprised of members of the Society of Abdominal Radiology Uterine and Ovarian Cancer Disease Focused Panel and the American Brachytherapy Society jointly assessed the existing literature and provide data-driven guidance on imaging protocol development, interpretation, and reporting.

RESULTS

Image-guidance during applicator implantation reduces rates of uterine perforation by the tandem. Postimplant images may be acquired with radiography, computed tomography (CT), or magnetic resonance imaging (MRI), and CT or MRI are preferred due to a decrease in severe complications. Pre-brachytherapy T2-weighted MRI may be used as a reference for contouring the high-risk clinical target volume (HR-CTV) when CT is used for treatment planning. Reference CT and MRI protocols are provided for reference.

CONCLUSIONS

Image-guided brachytherapy in locally advanced cervical cancer is essential for optimal patient management. Various imaging modalities, including orthogonal radiographs, ultrasound, computed tomography, and magnetic resonance imaging, remain integral to the successful execution of image-guided brachytherapy.

Prospective Evaluation of Prostate and Organs at Risk Segmentation Software for MRI-based Prostate Radiation Therapy

The segmentation of the prostate and surrounding organs at risk (OARs) is a necessary workflow step for performing dose-volume histogram analyses of prostate radiation therapy procedures. Low-dose-rate prostate brachytherapy (LDRPBT) is a curative prostate radiation therapy treatment that delivers a single fraction of radiation over a period of days. Prior studies have demonstrated the feasibility of fully convolutional networks to segment the prostate and surrounding OARs for LDRPBT dose-volume histogram analyses. However, performance evaluations have been limited to measures of global similarity between algorithm predictions and a reference. To date, the clinical use of automatic segmentation algorithms for LDRPBT has not been evaluated, to the authors' knowledge. The purpose of this work was to assess the performance of fully convolutional networks for prostate and OAR delineation on a prospectively identified cohort of patients who underwent LDRPBT by using clinically relevant metrics. Thirty patients underwent LDRPBT and were imaged with fully balanced steady-state free precession MRI after implantation. Custom automatic segmentation software was used to segment the prostate and four OARs. Dose-volume histogram analyses were performed by using both the original automatically generated contours and the physician-refined contours. Dosimetry parameters of the prostate, external urinary sphincter, and rectum were compared without and with the physician refinements. This study observed that physician refinements to the automatic contours did not significantly affect dosimetry parameters. Keywords: MRI, Neural Networks, Radiation Therapy, Radiation Therapy/Oncology, Genital/Reproductive, Prostate, Segmentation, Dosimetry Supplemental material is available for this article. © RSNA, 2022.

Advancing Research on Medical Image Perception by Strengthening Multidisciplinary Collaboration

Medical image interpretation is central to detecting, diagnosing, and staging cancer and many other disorders. At a time when medical imaging is being transformed by digital technologies and artificial intelligence, understanding the basic perceptual and cognitive processes underlying medical image interpretation is vital for increasing diagnosticians’ accuracy and performance, improving patient outcomes, and reducing diagnostician burn-out. Medical image perception remains substantially understudied. In September of 2019, the National Cancer Institute convened a multidisciplinary panel of radiologists and pathologists together with researchers working in medical image perception and adjacent fields of cognition and perception for the “Cognition and Medical Image Perception Think Tank.” The Think Tank’s key objectives were: to identify critical unsolved problems related to visual perception in pathology and radiology from the perspective of diagnosticians; to discuss how these clinically relevant questions could be addressed through cognitive and perception research; to identify barriers and solutions for transdisciplinary collaborations; to define ways to elevate the profile of cognition and perception research within the medical image community; to determine the greatest needs to advance medical image perception; and to outline future goals and strategies to evaluate progress. The Think Tank emphasized diagnosticians’ perspectives as the crucial starting point for medical image perception research, with diagnosticians describing their interpretation process and identifying perceptual and cognitive problems that arise. This paper reports the deliberations of the Think Tank participants to address these objectives and highlight opportunities to expand research on medical image perception.

Computer-aided segmentation on MRI for prostate radiotherapy, part II: Comparing human and computer observer populations and the influence of annotator variability on algorithm variability

BACKGROUND AND PURPOSE

Comparing deep learning (DL) algorithms to human interobserver variability, one of the largest sources of noise in human-performed annotations, is necessary to inform the clinical application, use, and quality assurance of DL for prostate radiotherapy.

MATERIALS AND METHODS

One hundred fourteen DL algorithms were developed on 295 prostate MRIs to segment the prostate, external urinary sphincter (EUS), seminal vesicles (SV), rectum, and bladder. Fifty prostate MRIs of 25 patients undergoing MRI-based low-dose-rate prostate brachytherapy were acquired as an independent test set. Groups of DL algorithms were created based on the loss functions used to train them, and the spatial entropy (SE) of their predictions on the 50 test MRIs was computed. Five human observers contoured the 50 test MRIs, and SE maps of their contours were compared with those of the groups of the DL algorithms. Additionally, similarity metrics were computed between DL algorithm predictions and consensus annotations of the 5 human observers' contours of the 50 test MRIs.

RESULTS

A DL algorithm yielded statistically significantly higher similarity metrics for the prostate than did the human observers (H) (prostate Matthew's correlation coefficient, DL vs. H: planning-0.931 vs. 0.903, p < 0.001; postimplant-0.925 vs. 0.892, p < 0.001); the same was true for the 4 organs at risk. The SE maps revealed that the DL algorithms and human annotators were most variable in similar anatomical regions: the prostate-EUS, prostate-SV, prostate-rectum, and prostate-bladder junctions.

CONCLUSIONS

Annotation quality is an important consideration when developing, evaluating, and using DL algorithms clinically.

Computer-aided segmentation on MRI for prostate radiotherapy, Part I: Quantifying human interobserver variability of the prostate and organs at risk and its impact on radiation dosimetry

BACKGROUND AND PURPOSE

Quantifying the interobserver variability (IoV) of prostate and periprostatic anatomy delineation on prostate MRI is necessary to inform its use for treatment planning, treatment delivery, and treatment quality assessment.

MATERIALS AND METHODS

Twenty five prostate cancer patients underwent MRI-based low-dose-rate prostate brachytherapy (LDRPBT). The patients were scanned with a 3D T2-weighted sequence for treatment planning and a 3D T2/T1-weighted sequence for quality assessment. Seven observers involved with the LDRPBT workflow delineated the prostate, external urinary sphincter (EUS), seminal vesicles, rectum, and bladder on all 50 MRIs. IoV was assessed by measuring contour similarity metrics, differences in organ volumes, and differences in dosimetry parameters between unique observer pairs. Measurements from a group of 3 radiation oncologists (G1) were compared against those from a group consisting of the other 4 clinical observers (G2).

RESULTS

IoV of the prostate was lower for G1 than G2 (Matthew's correlation coefficient [MCC], G1 vs. G2: planning-0.906 vs. 0.870, p < 0.001; postimplant-0.899 vs. 0.861, p < 0.001). IoV of the EUS was highest of all the organs for both groups, but was lower for G1 (MCC, G1 vs. G2: planning-0.659 vs. 0.402, p < 0.001; postimplant-0.684 vs. 0.398, p < 0.001). Large differences in prostate dosimetry parameters were observed (G1 maximum absolute prostate ΔD90: planning-76.223 Gy, postimplant-36.545 Gy; G1 maximum absolute prostate ΔV100: planning-13.927%, postimplant-8.860%).

CONCLUSIONS

While MRI is optimal in the management of prostate cancer with radiation therapy, significant interobserver variability of the prostate and external urinary sphincter still exist.

ACR Appropriateness Criteria® Staging and Follow-up of Primary Vaginal Cancer

Primary vaginal cancer is rare, comprising 1% to 2% of gynecologic malignancies and 20% of all malignancies involving the vagina. More frequently, the vagina is involved secondarily by direct invasion from malignancies originating in adjacent organs or by metastases from other pelvic or extrapelvic primary malignancies. Data on the use of imaging in vaginal cancer are sparse. Insights are derived from the study of imaging in cervical cancer and have reasonable generalizability to vaginal cancer due to similar tumor biology. Given the trend toward definitive chemoradiation for both cancers in all but early stage lesions, principles of postchemoradiation tumor response evaluation are largely analogous. Accordingly, many of the recommendations outlined here are informed by principles translated from the literature on cervical cancer. For pretreatment assessment of local tumor burden and in the case of recurrent vaginal cancer, MRI is the preferred imaging modality. PET/CT has demonstrated utility for the detection of nodal metastatic and unexpected distant metastatic disease. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Prospective trial of regional (hockey-stick) prostate cryoablation: oncologic and quality of life outcomes

PURPOSE

To report long-term follow-up of the efficacy of subtotal prostate ablation using a "hockey-stick" template, including oncologic control and quality of life (QoL) impact.

METHODS

We performed a prospective controlled trial to evaluate the efficacy of subtotal prostate ablation in selected men with baseline and confirmatory biopsy showing grade group (GG) 1-2 prostate cancer. "Hockey-stick" cryoablation that included the ipsilateral hemi-gland and contralateral anterior prostate was performed. Prostate biopsies and QOL queries were performed at 6, 18 and 36 months following regional ablation, and follow-up was updated to include subsequent clinic visits.

RESULTS

Between August 2009 and January 2012, 72 men were screened for eligibility and 47 opted to undergo confirmatory biopsy. Of these, 23 were deemed eligible and treated with regional cryoablation. Median age was 64 years. Median follow-up was 74 months. A single patient had < 1 mm of in-field viable tumor with therapy effect on 36-month biopsy. At time of last follow-up, a total of 12/23 (52%) patients did not have evidence of disease, all patients had preserved urinary control with no patients requiring pads for urinary incontinence. Sexual decline was significant at 3 and 6 months (P < 0.01 for both), though improvement was seen at subsequent time points.

CONCLUSION

Subtotal (hockey-stick template) cryoablation of the prostate provides oncologic control to targeted tissue in a generally low-risk group with minimal impact on sexual and urinary function. Further studies are needed to evaluate this ablation template in the MRI-targeted era and higher risk populations.

Definitive radiotherapy for extracranial oligoprogressive metastatic renal cell carcinoma as a strategy to defer systemic therapy escalation

OBJECTIVE

To study whether delivering definitive radiotherapy (RT) to sites of oligoprogression in metastatic renal cell carcinoma (mRCC) enabled deferral of systemic therapy (ST) changes without compromising disease control or survival.

PATIENTS AND METHODS

We identified patients with mRCC who received RT to three or fewer sites of extracranial progressive disease between 2014 and 2019 at a large tertiary cancer centre. Inclusion criteria were: (1) controlled disease for ≥3 months before oligoprogression, (2) all oligoprogression sites treated with a biologically effective dose of ≥100 Gy, and (3) availability of follow-up imaging. Time-to-event end-points were calculated from the start of RT.

RESULTS

A total of 72 patients were identified (median follow-up 22 months, 95% confidence interval [CI] 19-32 months), with oligoprogressive lesions in lung/mediastinum (n = 35), spine (n = 30), and non-spine bone (n = 5). The most common systemic therapies before oligoprogression were none (n = 33), tyrosine kinase inhibitor (n = 23), and immunotherapy (n = 13). At 1 year, the local control rate was 96% (95% CI 87-99%); progression-free survival (PFS), 52% (95% CI 40-63%); and overall survival, 91% (95% CI 82-96%). At oligoprogression, ST was escalated (n = 16), maintained (n = 49), or discontinued (n = 7), with corresponding median (95% CI) PFS intervals of 19.7 (8.2-27.2) months, 10.1 (6.9-13.2) months, and 9.8 (2.4-28.9) months, respectively. Of the 49 patients maintained on the same ST at oligoprogression, 21 did not subsequently have ST escalation.

CONCLUSION

Patients with oligoprogressive mRCC treated with RT had comparable PFS regardless of ST strategy, suggesting that RT may be a viable approach for delaying ST escalation. Randomised controlled trials comparing treatment of oligoprogression with RT vs ST alone are needed.

Efficacy of immune checkpoint blockade in patients with advanced upper tract urothelial cancer and mismatch repair deficiency or microsatellite instability (MSI)

487

Background: Tumors deficient in DNA mismatch repair (dMMR) exhibit a microsatellite unstable phenotype characterized by high tumor mutational burden and an immunogenic tumor microenvironment. Despite the histology-agnostic approval of pembrolizumab for advanced dMMR/MSI cancers, responsiveness of dMMR/MSI upper tract urothelial cancers (UTUC) to immune checkpoint (IC) blockade remains largely unknown. Methods: Consecutive records of patients (pts) from a single institution with locally advanced unresectable or metastatic dMMR/MSI UTUC who received IC therapy were analyzed. The primary endpoint was assessment of objective response rate (ORR) using RECIST v1.1. Secondary endpoints were progression-free survival (PFS) and overall survival (OS) using the Kaplan-Meier technique. dMMR/MSI status was evaluated by immunohistochemistry (IHC) and/or polymerase chain reaction (PCR). Results: Ten pts were identified with locally advanced unresectable (N = 3) or metastatic (N = 7) dMMR/MSI UTUC who received therapy with IC blockade (pembrolizumab = 7, nivolumab = 2, atezolizumab = 1). Median age was 65.5 (range = 46 – 90). Six pts were male. Seven pts had germline dMMR. MSI was detected by PCR in three pts and dMMR by IHC in seven pts (PMS2/MLH1 loss = 4, MSH2 loss = 1, MLH1 loss = 1, MSH6 loss = 1). Five pts received systemic chemotherapy (2 cisplatin based, 1 carboplatin based, 2 other) prior to IC therapy with two pts (40%) achieving partial response (PR). At a median follow-up of 15.5 months (range: 2 – 43 months), all pts were alive, and none experienced disease progression. PFS and OS at 15.5 months were 100%. The observed ORR was 90% (CI, 55.5%, 99.8%), including 8 pts who achieved complete remission (CR). The median time to best response was 4 months (range: 2 – 8 months). Toxicity leading to treatment discontinuation: 1 (grade 3) pancytopenia, 1 (grade 2) pneumonitis, 1 (grade 2) SICCA-like symptoms. Conclusions: Immunotherapy with IC inhibitors demonstrates excellent clinical activity in advanced dMMR/MSI UTUC. Further studies integrating these agents earlier in the disease course are warranted in this rare but important subgroup. Given the extremely high complete response rate in this population consideration of preference to IC therapy as initial therapy should be entertained if these findings are validated.

Fully Balanced SSFP Without an Endorectal Coil for Postimplant QA of MRI-Assisted Radiosurgery (MARS) of Prostate Cancer: A Prospective Study

PURPOSE

To investigate fully balanced steady-state free precession (bSSFP) with optimized acquisition protocols for magnetic resonance imaging (MRI)-based postimplant quality assessment of low-dose-rate (LDR) prostate brachytherapy without an endorectal coil (ERC).

METHODS AND MATERIALS

Seventeen patients at a major academic cancer center who underwent MRI-assisted radiosurgery (MARS) LDR prostate cancer brachytherapy were imaged with moderate, high, or very high spatial resolution fully bSSFP MRIs without using an ERC. Between 1 and 3 signal averages (NEX) were acquired with acceleration factors (R) between 1 and 2, with the goal of keeping scan times between 4 and 6 minutes. Acquisitions with R >1 were reconstructed with parallel imaging and compressed sensing (PICS) algorithms. Radioactive seeds were identified by 3 medical dosimetrists. Additionally, some of the MRI techniques were implemented and tested at a community hospital; 3 patients underwent MARS LDR prostate brachytherapy and were imaged without an ERC.

RESULTS

Increasing the in-plane spatial resolution mitigated partial volume artifacts and improved overall seed and seed marker visualization at the expense of reduced signal-to-noise ratio (SNR). The reduced SNR as a result of imaging at higher spatial resolution and without an ERC was partially compensated for by the multi-NEX acquisitions enabled by PICS. Resultant image quality was superior to the current clinical standard. All 3 dosimetrists achieved near-perfect precision and recall for seed identification in the 17 patients. The 3 postimplant MRIs acquired at the community hospital were sufficient to identify 208 out of 211 seeds implanted without reference to computed tomography (CT).

CONCLUSIONS

Acquiring postimplant prostate brachytherapy MRI without an ERC has several advantages including better patient tolerance, lower costs, higher clinical throughput, and widespread access to precision LDR prostate brachytherapy. This prospective study confirms that the use of an ERC can be circumvented with fully bSSFP and advanced MRI scan techniques in a major academic cancer center and community hospital, potentially enabling postimplant assessment of MARS LDR prostate brachytherapy without CT.

Detecting recurrent prostate Cancer using multiparametric MRI, influence of PSA and Gleason grade

Background

The utility of multiparametric MRI (mpMRI) in detecting suspected local recurrence post radical prostatectomy (RP) may be associated with PSA and Gleason grade. The purpose of the study was to evaluate the likelihood of detecting locally recurrent prostate cancer utilizing mpMRI in patients with suspected recurrence following radical prostatectomy (RP) parsed by PSA and Gleason grade.

Methods

One hundred ninety five patients with suspected local recurrence were imaged on a 1.5 T MRI with torso array and endorectal coil in this retrospective study. mpMRI interpretations were stratified by PSA and lower (Gleason < 7) vs. higher grade tumors (Gleason 8–10). Recursive partitioning was used to determine whether mpMRI interpretations could be classified as positive or negative.

Results

The majority of mpMRI interpretations in patients with lower Gleason grade tumors and PSA < 0.5 ng/mL were negative (68/78, 87.2%, p = 0.004). The majority of mpMRI interpretations in patients with higher Gleason grade tumors and PSA > 1.5 ng/mL were positive (8/9, 88.9%, p = 0.003). Findings were corroborated by recursive partitioning, which identified a PSA = 0.5 ng/ml in patients with lower grade tumors and a PSA = 1.5 ng/mL in patients with higher grade tumors as differentiating negative and positive mpMRIs.

Conclusion

In the setting of suspected recurrence after RP, mpMRI results are associated with PSA and Gleason grade, both of which can help guide when mpMRI may find utility. mpMRI is likely to be low diagnostic yield and negative for recurrence (87%) in the setting of lower Gleason grade tumors and PSA < 0.5 ng/mL. mpMRI is likely to be of low diagnostic value and positive for recurrence (89%) in the setting of PSA > 1.5 ng/mL and higher grade tumors; in this case, mpMRI findings may be more useful for directing biopsy and local therapy. Between these extremes, PSA > 0.5 ng/mL and lower grade tumors or PSA < 1.5 ng/mL and higher grade tumors, mpMRI results are less predictable, suggesting greater diagnostic value for detecting recurrence post prostatectomy.

Results of a multicenter, phase 2 study of nivolumab and ipilimumab for patients with advanced rare genitourinary malignancies

BACKGROUND

In this multicenter, single-arm, multicohort, phase 2 trial, the efficacy of nivolumab and ipilimumab was evaluated in patients with advanced rare genitourinary cancers, including bladder and upper tract carcinoma of variant histology (BUTCVH), adrenal tumors, platinum-refractory germ cell tumors, penile carcinoma, and prostate cancer of variant histology (NCT03333616).

METHODS

Patients with rare genitourinary malignancies and no prior immune checkpoint inhibitor exposure were enrolled. Patients received nivolumab at 3 mg/kg and ipilimumab at 1 mg/kg intravenously every 3 weeks for 4 doses, and this was followed by 480 mg of nivolumab intravenously every 4 weeks. The primary endpoint was the objective response rate (ORR) by the Response Evaluation Criteria in Solid Tumors (version 1.1).

RESULTS

Fifty-five patients were enrolled at 6 institutions between April 2018 and July 2019 in 3 cohorts: BUTCVH (n = 19), adrenal tumors (n = 18), and other tumors (n = 18). The median follow-up was 9.9 months (range, 1 to 21 months). Twenty-eight patients (51%) received 4 doses of nivolumab and ipilimumab; 25 patients received nivolumab maintenance for a median of 4 cycles (range, 1-18 cycles). The ORR for the entire study was 16% (80% confidence interval, 10%-25%); the ORR in the BUTCVH cohort, including 2 complete responses, was 37%, and it was 6% in the other 2 cohorts. Twenty-two patients (40%) developed treatment-related grade 3 or higher toxicities; 24% (n = 13) required high-dose steroids (≥40 mg of prednisone or the equivalent). Grade 5 events occurred in 3 patients; 1 death was treatment related.

CONCLUSIONS

Nivolumab and ipilimumab resulted in objective responses in a subset of patients with rare genitourinary malignancies, especially those with BUTCVH. An additional cohort exploring their activity in genitourinary tumors with neuroendocrine differentiation is ongoing.

LAY SUMMARY

Patients with rare cancers are often excluded from studies and have limited treatment options. Fifty-five patients with rare tumors of the genitourinary system were enrolled from multiple sites and were treated with nivolumab and ipilimumab, a regimen used for kidney cancer. The regimen showed activity in some patients, particularly those with bladder or upper tract cancers of unusual or variant histology; 37% of those patients responded to therapy. Additional studies are ongoing to better determine who benefits the most from this combination.

ACR Appropriateness Criteria® Recurrent Lower Urinary Tract Infections in Females

Urinary tract infections (UTIs) in women are common, with an overall lifetime risk over >50%. UTIs are considered recurrent when they follow complete clinical resolution of a previous UTI and are usually defined as at least three episodes of infection within the preceding 12 months. An uncomplicated UTI is classified as a UTI without structural or functional abnormalities of the urinary tract and without relevant comorbidities. Complicated UTIs are those occurring in patients with underlying structural or medical problems. In women with recurrent uncomplicated UTIs, cystoscopy and imaging are not routinely used. In women suspected of having a recurrent complicated UTI, cystoscopy and imaging should be considered. CT urography or MR urography are usually appropriate for the evaluation of recurrent complicated lower urinary tract infections or for women who are nonresponders to conventional therapy, develop frequent reinfections or relapses, or have known underlying risk factors. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Post-Treatment Surveillance of Bladder Cancer

Urothelial cancer is the second most common cancer, and cause of cancer death, related to the genitourinary tract. The goals of surveillance imaging after the treatment of urothelial cancer of the urinary bladder are to detect new or previously undetected urothelial tumors, to identify metastatic disease, and to evaluate for complications of therapy. For surveillance, patients can be stratified into one of three groups: (1) nonmuscle invasive bladder cancer with no symptoms or additional risk factors; (2) nonmuscle invasive bladder cancer with symptoms or additional risk factors; and (3) muscle invasive bladder cancer. This article is a review of the current literature for urothelial cancer and resulting recommendations for surveillance imaging. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Combination therapy with nivolumab and tyrosine kinase inhibitors in patients with metastatic renal cell carcinoma

e17090

Background: Two immunotherapy (IO) and tyrosine kinase inhibitor (TKI) combinations are FDA-approved for patients (pts) with metastatic renal cell carcinoma (mRCC). Here we present a multicenter off-protocol experience with IO/TKI combinations after progression on monotherapy. Methods: We performed a retrospective analysis of pts with mRCC who received combination non-FDA approved off-protocol IO/TKI combination therapy from 11/2015 – 1/2019 at MD Anderson Cancer Center and Duke Cancer Institute. Results: 48 pts met criteria for study inclusion. At therapy start: median (med) age 65 years; 75% clear cell histology; 68.8% IMDC intermediate risk (20.8% favorable, 10.4% poor); 81.3% prior nephrectomy; med metastatic sites: 2; med prior systemic treatments: 2; most common metastatic sites: lung (58.3%), lymph node (52.1%), and bone (43.8%). Pts received nivolumab (nivo) in combination with the following: cabozantinib (n = 24, 50%), pazopanib (13, 27.1%), axitinib (6, 12.5%), lenvatinib (2, 4.2%), ipilimumab/cabozantinib (3, 6.3%). Med PFS was 13.7 months and med OS was not reached. The two largest cohorts received nivo + cabozantinib (N+C; med dose 40 mg daily) or nivo + pazopanib (N+P; med dose 400 mg daily). The N+C cohort had higher med metastatic sites (3 vs 2) and was more pretreated with agents unique to their IO/TKI combination (med 2 vs 0). In the N+P group, more pts had started on TKI prior to addition of nivo at progression (69.2% vs 45.8%), and fewer had IO monotherapy with TKI addition (30.8% vs 50%). With a med follow up of 14.0 months after combination start, the N+C cohort had a med PFS of 7.3 months (initiated TKI first: 4.8, IO first: 8.2) and med OS of 18.2 months (TKI first: 11.8, IO first: 24.3). The N+P cohort had med follow up of 20.5 months after combination, med PFS of 21.3 months (TKI first: 16.5, IO first: 21.8), and med OS was not reached. In the N+C group, 87.5% experienced any grade adverse event (AE), most common included fatigue (79.2%), diarrhea (42.7%), nausea (29.2%), hypertension (29.2%), and weight loss (25.0%). In the N+P group, 92.3% experienced any grade AE, including fatigue (76.9%), hypertension (38.5%), diarrhea (30.8%), nausea (30.8%), and weight loss (30.8%). There were no grade ≥3 AEs. Conclusions: Slow disease progression on nivo or TKI may be safely controlled with addition of IO/TKI therapy. Med PFS after addition of nivo to TKI appears similar (N+C) and improved (N+P) compared to nivo monotherapy (Checkmate-025). Med PFS after addition of TKI to IO was also similar (N+C) and improved (N+P) compared to historical controls.

Phase II study of nivolumab and ipilimumab for advanced rare genitourinary cancers

5018

Background: Patients with rare genitourinary malignancies (Bladder cancer of variant histologies (BCVH), adrenal tumors, chemotherapy refractory germ cell tumors (CRGCT), penile carcinoma and prostate cancer of variant histology (PCVH)) have poor outcomes. Nivolumab and ipilimumab has demonstrated safety and efficacy in genitourinary malignancies. In this multicenter, single arm, multi-cohort phase II trial we evaluated the efficacy of nivolumab and ipilimumab in pts with advanced rare genitourinary cancers (NCT 03333616). Herein, we report the results of the fully accrued BCVH, adrenal and other cohorts. Methods: Eligible pts had a metastatic rare genitourinary malignancy, ECOG performance status of 0-2 and no prior immune checkpoint inhibitor exposure; aside from CRGCT pts could be treatment naïve. Eligible pts received nivolumab 3 mg/kg and ipilimumab 1 mg/kg intravenously every 3 weeks for 4 doses with continued nivolumab 480 mg IV every 4 weeks. The primary endpoint was overall response rate (ORR) by RECIST 1.1. Results: 56 pts were enrolled at 6 institutions between 4/2018 and 7/2019 in 3 cohorts: BCVH (N = 19), adrenal tumors (n = 18) and other tumors (n = 19). Median follow-up was 9.9 (range < 1~21) months. 28(50%) pts received all 4 doses of nivolumab and ipilimumab. 25 pts received nivolumab maintenance at a median of 4 (range 1-18) cycles. ORR in entire cohort was 16% (n = 9: 2 CR 7 PR, Table); 67% of responders (6/9) maintained response greater than 9 months. Median PFS was 2.8 (2.7-5.2) months. 22 pts (39%) developed treatment-related ≥ grade 3 toxicity; 23% required high dose steroids (≥40 mg prednisone or equivalent) and 15 (27%) pts discontinued treatment due to an AE. Grade 5 toxicity occurred in 3 pts; 1 death was treatment related. Conclusions: Nivolumab and ipilimumab resulted in objective responses in a subset of pts with rare GU malignancies, especially in BCVH. Biomarkers are being evaluated and an additional cohort exploring the activity in genitourinary tumors with neuroendocrine differentiation is ongoing. This combination warrants further investigation in these pts with substantial unmet needs. Clinical trial information: NCT 03333616 . [Table: see text]

Quality comparison between three-dimensional T2-weighted SPACE and two-dimensional T2-weighted turbo spin echo magnetic resonance images for the brachytherapy planning evaluation of prostate and periprostatic anatomy

PURPOSE

The purpose of this study was to compare an isotropic three-dimensional (3D) T2-weighted sequence sampling perfection with application-optimized contrasts by using flip angle evolution (SPACE) with an axial two-dimensional T2-weighted turbo spin echo (TSE) sequence with regard to overall image quality and the delineation of normal prostate and periprostatic anatomy for low-dose-rate prostate cancer brachytherapy planning evaluation.

METHODS AND MATERIALS

Patients (n = 69) with prostate cancer who had pelvic magnetic resonance imaging (MRI) for low-dose-rate brachytherapy treatment planning were included. Three radiologists independently assessed the visibility of nine anatomic structures on each sequence by using a 5-point scale and overall image quality by using a 4-point scale. The significance of the differences in diagnostic performance was tested with a Wilcoxon signed rank test.

RESULTS

No significant intersequence differences were found for most (7/9) anatomical structures and overall image quality. The mean scores for visibility of anatomical structures on the 3D SPACE and 2D TSE sequences, respectively, were as follows: the zonal anatomy (3.7; 3.9, p = 0.05), prostate capsule (3.9; 4.0, p = 0.08), neurovascular bundle (2.9; 2.9, p = 0.9), rectoprostatic angle (3.8; 3.8, p = 0.35), rectum (4.2; 4.3, p = 0.26), urethra (3.8; 3.9, p = 0.12), urinary bladder (4.6; 4.6, p = 0.61), and overall image quality (2.9; 2.9, p = 0.33). 3D SPACE was superior for delineation of the genitourinary diaphragm (3.8; 3.6, p = 0.003), whereas 2D TSE was superior for delineation of the seminal vesicles (3.5; 4.0, p < 0.0001).

CONCLUSIONS

Anatomic delineation of the prostatic and periprostatic anatomy provided by the 3D SPACE sequence is as robust in quality as that provided by a conventional 2D TSE sequence with superior delineation of the genitourinary diaphragm. For MRI-based brachytherapy treatment planning, the 3D SPACE sequence with subcentimeter isotropic resolution can replace the 2D TSE sequence and be incorporated into standard MRI protocols.

Modeling Complex Deformations of the Sigmoid Colon Between External Beam Radiation Therapy and Brachytherapy Images of Cervical Cancer

PURPOSE

In this study, we investigated registration methods for estimating the large interfractional sigmoid deformations that occur between external beam radiation therapy (EBRT) and brachytherapy (BT) for cervical cancer.

METHODS AND MATERIALS

Sixty-three patients were retrospectively analyzed. The sigmoid colon was delineated on 2 computed tomography images acquired during EBRT (without applicator) and BT (with applicator) for each patient. Five registration approaches were compared to propagate the contour of the sigmoid from BT to EBRT anatomies: rigid registration, commercial hybrid (ANAtomically CONstrained Deformation Algorithm), controlling ROI surface projection of RayStation, and the classical and constrained symmetrical thin-plate spline robust point matching (sTPS-RPM) methods. Deformation of the sigmoid due to insertion of the BT applicator was reported. Registration performance was compared by using the Dice similarity coefficient (DSC), distance to agreement, and Hausdorff distance. The 2 sTPS-RPM methods were compared by using surface triangle quality criteria between deformed surfaces. Using the deformable approaches, the BT dose of the sigmoid was deformed toward the EBRT anatomy. The displacement and discrepancy between the deformable methods to propagate the planned D1cm³ and D2cm³ of the sigmoid from BT to EBRT anatomies were reported for 55 patients.

RESULTS

Large and complex deformations of the sigmoid were observed for each patient. Rigid registration resulted in poor sigmoid alignment with a mean DSC of 0.26. Using the contour to drive the deformation, ANAtomically CONstrained Deformation Algorithm was able to slightly improve the alignment of the sigmoid with a mean DSC of 0.57. Using only the sigmoid surface as controlling ROI, the mean DSC was improved to 0.79. The classical and constrained sTPS-RPM methods provided mean DSCs of 0.95 and 0.96, respectively, with an average inverse consistency error <1 mm. The constrained sTPS-RPM provided more realistic deformations and better surface topology of the deformed sigmoids. The planned mean (range) D1cm³ and D2cm³ of the sigmoid were 13.4 Gy (1-24.1) and 12.2 Gy (1-21.5) on the BT anatomy, respectively. Using the constrained sTPS-RPM to deform the sigmoid from BT to EBRT anatomies, these hotspots had a mean (range) displacement of 27.1 mm (6.8-81).

CONCLUSIONS

Large deformations of the sigmoid were observed between the EBRT and BT anatomies, suggesting that the D1cm³ and D2cm³ of the sigmoid would unlikely to be at the same position throughout treatment. The proposed constrained sTPS-RPM seems to be the preferred approach to manage the large deformation due to BT applicator insertion. Such an approach could be used to map the EBRT dose to the BT anatomy for personalized BT planning optimization.

MRI for Radiation Therapy Planning in Human Papillomavirus-associated Gynecologic Cancers

Locally advanced human papillomavirus (HPV)-associated gynecologic cancers, including cervical, vaginal, and vulvar cancers, are treated primarily with radiation therapy (RT). Cervical cancer remains a leading cause of cancer death among women worldwide. The superior soft-tissue resolution of MRI compared with other imaging modalities makes it an ideal modality for RT planning, execution, and follow-up of these malignancies. This superiority has been corroborated in the literature when comparing MRI-based RT planning to radiography-based conventional treatment planning approaches. In 2005, the Groupe Européen de Curiethérapie and the European Society for Radiation Therapy and Oncology guidelines underscored the central role of MRI for successful implementation of three-dimensional image-based cervical cancer brachytherapy. The delineation of both gross tumor volume and clinical tumor volume for brachytherapy is performed at the time of each brachytherapy application, on the basis of the findings depicted on anatomic MR images. Contemporary knowledge concerning the role of MRI for RT planning in HPV-associated gynecologic cancers warrants an understanding of the epidemiology and clinical manifestations of these cancers, as well as knowledge of MRI protocol for cancer staging, selection of RT candidates, brachytherapy implant assessment, posttreatment surveillance, and delineation of treatment-related complications. Technical requirements, patient preparation, and image acquisition protocols are detailed in this review, and imaging-based treatment protocols are summarized. Knowledge of these fundamental concepts enables the radiologist to play an important role in diagnosis, staging, and posttreatment follow-up, helping to guide radiation oncologists and other clinicians in the management of these malignancies.^©RSNA, 2019.

Deep learning application engine (DLAE): Development and integration of deep learning algorithms in medical imaging

Herein we introduce a deep learning (DL) application engine (DLAE) system concept, present potential uses of it, and describe pathways for its integration in clinical workflows. An open-source software application was developed to provide a code-free approach to DL for medical imaging applications. DLAE supports several DL techniques used in medical imaging, including convolutional neural networks, fully convolutional networks, generative adversarial networks, and bounding box detectors. Several example applications using clinical images were developed and tested to demonstrate the capabilities of DLAE. Additionally, a model deployment example was demonstrated in which DLAE was used to integrate two trained models into a commercial clinical software package.

Phase II study of nivolumab and ipilimumab for advanced bladder cancer of variant histologies (BCVH)

4518

Background: Patients with BCVH have poor outcomes and data regarding the management of this heterogeneous group of patients is limited. Nivolumab and ipilimumab has demonstrated safety and efficacy in urothelial carcinoma and other malignancies. In this multicenter, single arm, multi-cohort phase II trial we evaluate the efficacy of nivolumab and ipilimumab in patients with BCVH and other advanced rare genitourinary cancers (NCT 03333616). Herein, we report the preliminary results of the fully accrued BCVH cohort. Methods: Eligible patients had metastatic BCVH, ECOG performance status of 0-2 and were either untreated or had received any number of lines of prior therapy excluding prior immunotherapy. Patients underwent a baseline biopsy and blood collection for correlative studies and received treatment with nivolumab 3 mg/kg and ipilimumab 1 mg/kg intravenously every 3 weeks for 4 cycles with continued maintenance of nivolumab 480 mg IV every 4 weeks. The primary endpoint was overall response rate (ORR) by RECIST 1.1. Results: 19 BCVH patients were enrolled at 4 institutions between 4/2018 and 1/2019: squamous cell (n = 6), small cell (n = 3), adenocarcinoma (n = 3), urachal (n = 5), plasmacytoid (n = 1), and spindle cell (n = 1). 13 (68%) patients had received prior systemic therapy including platinum-based chemotherapy in 92% patients. Median number of cycles of ipilimumab plus nivolumab received was 3 (range 1-8) and median follow-up was 3.6 (0.3-8.8) months. 13 patients had undergone at least one scan; ORR was 31% (4/13, 80%CI: 14-52%), with partial responses seen in small cell carcinoma (n = 2), urachal (n = 1) and a complete response in 1 patient with plasmacytoid carcinoma. 3 patients (16%) developed treatment-related grade 3 toxicities with 1 (5%) grade 4 toxicity. Conclusions: Nivolumab and ipilmumab resulted in objective responses in a subset of patients with BCVH with manageable toxicities. Updated clinical and correlative data will be presented. This combination may warrant further investigation in patients with BCVH, which has substantial unmet needs. Clinical trial information: NCT 03333616.

Combination anti-angiogenic tyrosine kinase inhibition and anti-PD1 immunotherapy in metastatic renal cell carcinoma: A retrospective analysis of safety, tolerance, and clinical outcomes

630

Background: Emerging phase III data support combination antiangiogenic tyrosine kinase inhibitors (TKIs) and immunotherapy (IO) as front line treatment for metastatic renal cell carcinoma (mRCC). Little is known about off-protocol experience and later line treatment with this therapeutic approach including tolerance, response and survival. Methods: We conducted a retrospective analysis of mRCC patients (pts) who received combination TKI-IO between 11/2015 and 05/2018 at MD Anderson Cancer Center. Chart review detailed baseline characteristics, TKI-IO treatment, toxicity and survival. An independent radiologist, blinded to pts history and clinical data, assessed radiographic response using RECIST v1.1. Results: 36 mRCC pts were identified for study inclusion: median (med) age 63.5 years, 72% clear cell histology, 53% intermediate risk (19% good, 28% poor) by IMDC, med metastatic sites 2, med prior therapies 2, previous TKI 94% and previous IO 47%. Combinations included nivolumab (nivo)-cabozantinib (15), nivo-low dose pazopanib(ldP) (13), nivo-axitinib (5), nivo-lenvatinib (2) and pembrolizumab-axitinib (1). Median time on TKI-IO was 5.6 months (m) (95% CI: 5.2 - 7.7). 56% of pts initiated TKI prior to IO addition at progression and 36% of pts initiated IO prior to TKI addition. ORR was 35% (29% PR and 6% CR); disease control rate was 78% (43% stable disease). With med follow-up of 8.0 m (95% CI: 6.4 – 9.4), med PFS was 7.7 m (95%CI: 5.8 - 9.5), med OS was not reached. Med PFS for pts receiving nivo-ldP was not reached. TKI-IO therapy was well tolerated with only 1 pt demonstrating grade 3 or 4 immune related toxicity (nephritis). 92% of pts experienced any grade of adverse events (ADE) with ADE of interest as follows: diarrhea (25%), hypothyroidism (17%), and pneumonitis (8%). Conclusions: To our knowledge, this is the first case series of off-label combinations of TKI-IO for mRCC. TKI-IO, particularly nivo-ldP, is safe, well tolerated and efficacious. Although further prospective research is essential, TKI-IO could be considered for select mRCC patients, particularly in the setting of TKI or IO refractory disease.

Cabozantinib for the treatment of patients with metastatic non-clear cell renal cell carcinoma: A retrospective analysis

BACKGROUND

Cabozantinib prolongs overall survival (OS) and progression-free survival (PFS) in patients with metastatic clear cell renal cell carcinoma (RCC) that progressed on first-line vascular endothelial growth factor receptor-tyrosine kinase inhibitor (VEGFR-TKI). The role of cabozantinib has not been established in non-clear cell renal cell carcinoma (nccRCC).

METHODS

This is a retrospective study of 30 patients with nccRCC who received cabozantinib from January 2013 to January 2017. Information collected included baseline characteristics, toxicity, dose reductions, PFS and OS. A fellowship trained abdominal radiologist, blinded to patient history and clinical data, assessed radiographic response using RECIST, v1.1.

RESULTS

With a median follow-up of 20.6 months (95% confidence interval [CI]: 11.4-28.8), median PFS was 8.6 months (95% CI: 6.1-14.7), and median OS was 25.4 months (95% CI: 15.5-35.4). Of the 28 patients with measurable disease, 4 had partial responses (2 papillary, 1 chromophobe and 1 unclassified RCC), 18 had stable disease (64.2%) and 6 had progressive disease (21.4%), resulting in a 14.3% objective response rate and a 78.6% disease control rate. Two patients with papillary RCC who had experienced disease progression on savolitinib achieved durable partial response and stable disease, respectively, following treatment with cabozantinib. Of the 21 patients who started cabozantinib at 60 mg/d, 12 (57.1%) required dose reduction due to toxicity.

CONCLUSION

In this retrospective study, cabozantinib produced a clinically meaningful benefit in patients with metastatic nccRCC, the majority of whom had disease progression on prior VEGFR-TKIs. Prospective trials of cabozantinib in nccRCC are warranted.

Conditional survival of patients with small renal masses undergoing active surveillance

OBJECTIVES

To determine conditional survival for patients with small renal masses (SRMs) undergoing active surveillance (AS).

MATERIALS AND METHODS

Patients were enrolled in a prospective AS protocol at our institution between May 2005 and January 2016. Patients with SRMs ≤4 cm with serial cross-sectional imaging available in-house for review were included. Overall survival (OS) was estimated using the Kaplan-Meier method and modelled via Cox proportional hazards models. The primary endpoints analysed were the conditional probability of survival and tumour growth over time. Landmark analysis was used to evaluate survival outcomes beyond the 2-year mark after the initial scan. The relative conditional survival of patients on AS was compared to those undergoing partial nephrectomy (PN) using inverse probability of treatment weighting.

RESULTS

A total of 272 patients were included in this analysis. The mean initial SRM size was 1.74 ± 0.77 cm, and the mean mass size closest to the 2-year mark was 1.97 ± 0.83 cm. The likelihood of continued survival to 5 years improved after the 2-year landmark. Patients with masses <3 cm who survived the first 2 years on AS had a 0.84-0.85 chance of surviving to 5 years, and if they survived 3 years, the probability of surviving to 5 years improved to 0.91. A slow tumour growth (β: 0.12; P < 0.001) with parallel growth rates was found for tumours <3 cm. Patients on AS and those who underwent PN had similar OS for ~7 years, beyond which PN demonstrated a trend of lower risk of death compared with AS (hazard ratio 0.57; P = 0.07).

CONCLUSIONS

The conditional survival probability of patients with SRMs <3 cm on AS increased after 2 years. This information may prove useful to urologists and patients who are considering continuing AS vs intervention after the first 2 years on AS.