An IMRT planning technique for treating whole breast or chest wall with regional lymph nodes on Halcyon and Ethos

PURPOSE/OBJECTIVE

Field size limitations on Halcyon and Ethos treatment machines largely preclude use of the conventional monoisocentric three-field technique for breast/chest wall and regional lymph nodes. We present an alternative, IMRT-based planning approach that facilitates treatment on Halcyon and Ethos while preserving plan quality.

MATERIALS/METHODS

Eight breast and regional node cases (four left-sided, four right-sided) were planned for an Ethos machine using a 15-17 field IMRT technique. Institutional plan quality metrics for CTV and PTV coverage and OAR sparing were assessed. Five plans (four right-sided, one left-sided) were also planned using a hybrid 3D multisocenter technique. CTV coverage and OAR sparing were compared to the IMRT plans. Eclipse scripting tools were developed to aid in beam placement and plan evaluation through a set of dosimetric scorecards, and both are shared publicly.

RESULTS

On average, the IMRT plans achieved breast CTV and PTV coverage at 50 Gy of 97.9% and 95.7%, respectively. Supraclavicular CTV and PTV coverages at 45 Gy were 100% and 95.5%. Axillary lymph node CTV and PTV coverages at 45 Gy were 100% and 97.1%, and IMN CTV coverage at 45 Gy was 99.2%. Mean ipsilateral lung V20 Gy was 19.3%, and average mean heart dose was 1.6 Gy for right-sided cases and 3.0 Gy for left-sided. In comparison to the hybrid 3D plans, IMRT plans achieved higher breast and supraclavicular CTV coverage (99.9% vs. 98.6% and 99.9% vs. 93.4%), higher IMN coverage (99.6% vs. 78.2%), and lower ipsilateral lung V20 Gy (19.6% vs. 28.2%).

CONCLUSION

Institutional plan quality benchmarks were achieved for all eight cases using the IMRT-based planning approach. The IMRT-based planning approach offered superior conformity and OAR sparing than a competing hybrid 3D approach.

Multiparametric MRI as a Predictor of PSA Response in Patients Undergoing Stereotactic Body Radiation Therapy for Prostate Cancer

Purpose

To maximize the therapeutic ratio, it is important to identify adverse prognostic features in men with prostate cancer, especially among those with intermediate risk disease, which represents a heterogeneous group. These men may benefit from treatment intensification. Prior studies have shown pretreatment mpMRI may predict biochemical failure in patients with intermediate and/or high-risk prostate cancer undergoing conventionally fractionated external beam radiation therapy and/or brachytherapy. This study aims to evaluate pretreatment mpMRI findings as a marker for outcome in patients undergoing stereotactic body radiation therapy (SBRT).

Methods and Materials

We identified all patients treated at our institution with linear accelerator based SBRT to 3625 cGy in 5 fractions, with or without androgen deprivation therapy (ADT) from November 2015 to March 2021. All patients underwent pretreatment Magnetic Resonance Imaging (MRI). Posttreatment Prostate Specific Imaging (PSA) measurements were typically obtained 4 months after SBRT, followed by every 3 to 6 months thereafter. A 2 sample t test was used to compare preoperative mpMRI features with clinical outcomes.

Results

One hundred twenty-three men were included in the study. Pretreatment MRI variables including median diameter of the largest intraprostatic lesion, median number of prostate lesions, and median maximal PI-RADS score, were each predictive of PSA nadir and time to PSA nadir (P < .0001). When separated by ADT treatment, this association remained for patients who were not treated with ADT (P < .001). In patients who received ADT, the pretreatment MRI variables were each significantly associated with time to PSA nadir (P < .01) but not with PSA nadir (P > 0.30). With a median follow-up time of 15.9 months (IQR: 8.5-23.3), only 3 patients (2.4%) experienced biochemical recurrence as defined by the Phoenix criteria.

Conclusions

Our experience shows the significant ability of mpMRI for predicting PSA outcome in prostate cancer patients treated with SBRT with or without ADT. Since PSA nadir has been shown to correlate with biochemical failure, this information may help radiation oncologists better counsel their patients regarding outcome after SBRT and can help inform future studies regarding who may benefit from treatment intensification with, for example, ADT and/or boosts to dominant intraprostatic lesions.

Multicenter Study of Pelvic Nodal Autosegmentation Algorithm of Siemens Healthineers: Comparison of Male Versus Female Pelvis

Purpose

The autosegmentation algorithm of Siemens Healthineers version VA 30 (AASH) (Siemens Healthineers, Erlangen, Germany) was trained and developed in the male pelvis, with no published data on its usability in the female pelvis. This is the first multi-institutional study to describe and evaluate an artificial intelligence algorithm for autosegmentation of the pelvic nodal region by gender.

Methods and Materials

We retrospectively evaluated AASH pelvic nodal autosegmentation in both male and female patients treated at our network of institutions. The automated pelvic nodal contours generated by AASH were evaluated by 1 board-certified radiation oncologist. A 4-point scale was used for each nodal region contour: a score of 4 is clinically usable with minimal edits; a score of 3 requires minor edits (missing nodal contour region, cutting through vessels, or including bowel loops) in 3 or fewer computed tomography slices; a score of 2 requires major edits, as previously defined but in 4 or more computed tomography slices; and a score of 1 requires complete recontouring of the region. Pelvic nodal regions included the right and left side of the common iliac, external iliac, internal iliac, obturator, and midline presacral nodes. In addition, patients were graded based on their lowest nodal contour score. Statistical analysis was performed using Fisher exact tests and Yates-corrected χ2 tests.

Results

Fifty-two female and 51 male patients were included in the study, representing a total of 468 and 447 pelvic nodal regions, respectively. Ninety-six percent and 99% of contours required minor edits at most (score of 3 or 4) for female and male patients, respectively (P = .004 using Fisher exact test; P = .007 using Yates correction). No nodal regions had a statistically significant difference in scores between female and male patients. The percentage of patients requiring no more than minor edits was 87% (45 patients) and 92% (47 patients) for female and male patients, respectively (P = .53 using Fisher exact test; P = .55 using Yates correction).

Conclusions

AASH pelvic nodal autosegmentation performed very well in both male and female pelvic nodal regions, although with better male pelvic nodal autosegmentation. As autosegmentation becomes more widespread, it may be important to have equal representation from all sexes in training and validation of autosegmentation algorithms.

Scorecards: Quantifying Dosimetric Plan Quality in Pancreatic Ductal Adenocarcinoma Stereotactic Body Radiation Therapy

Purpose

A scoring mechanism called the scorecard that objectively quantifies the dosimetric plan quality of pancreas stereotactic body radiation therapy treatment plans is introduced.

Methods and Materials

A retrospective analysis of patients with pancreatic ductal adenocarcinoma receiving stereotactic body radiation therapy at our institution between November 2019 and November 2020 was performed. Ten patients were identified. All patients were treated to 36 Gy in 5 fractions, and organs at risk (OARs) were constrained based on Alliance A021501. The scorecard awarded points for OAR doses lower than those cited in Alliance A021501. A team of 3 treatment planners and 2 radiation oncologists, including a physician resident without plan optimization experience, discussed the relative importance of the goals of the treatment plan and added additional metrics for OARs and plan quality indexes to create a more rigorous scoring mechanism. The scorecard for this study consisted of 42 metrics, each with a unique piecewise linear scoring function which is summed to calculate the total score (maximum possible score of 365). The scorecard-guided plan, the planning and optimization for which were done exclusively by the physician resident with no prior plan optimization experience, was compared with the clinical plan, the planning and optimization for which were done by expert dosimetrists, using the Sign test.

Results

Scorecard-guided plans had, on average, higher total scores than those clinically delivered for each patient, averaging 280.1 for plans clinically delivered and 311.7 for plans made using the scorecard (P = .003). Additionally, for most metrics, the average score of each metric across all 10 patients was higher for scorecard-guided plans than for clinically delivered plans. The scorecard guided the planner toward higher coverage, conformality, and OAR sparing.

Conclusions

A scorecard tool can help clarify the goals of a treatment plan and provide an objective method for comparing the results of different plans. Our study suggests that a completely novice treatment planner can use a scorecard to create treatment plans with enhanced coverage, conformality, and improved OAR sparing, which may have significant effects on both tumor control and toxicity. These tools, including the scorecard used in this study, have been made freely available.

Dosimetric Study of Total Marrow and Lymphoid Irradiation on a Ring Gantry-Based Medical Linac with a Two-Layer Multi-Leaf Collimator

PURPOSE/OBJECTIVE(S)

In this study, we aimed to evaluate dosimetric quality of total marrow and lymphoid irradiation (TMLI) plans for a ring gantry-based medical Linac with a two-layer multi-leaf collimator.

MATERIALS/METHODS

We retrospectively retrieved treatment planning CT images, structure sets, and plan dose for four adult patients, two male and two female, who previously received TMLI treatments on helical tomotherapy (HT) at our institution. TMLI plans were optimized for a ring gantry-based medical Linac with a two-layer multi-leaf collimator (Halcyon, Varian Medical Systems, Inc., Palo Alto, CA). A prescription dose of 12 Gy in 8 fractions was prescribed to the skeletal bones from the skull to mid-thigh, spleen, spinal canal, and lymphoid volume. Five or six isocenters were placed with equal spacing along the patient's longitudinal direction in each TMLI plan with two 6-MV flattening filter-free volumetric modulated arc therapy (VMAT) fields at each isocenter. Isocenter separation ranged from 15 cm to 16.5 cm. Each VMAT field has a field size of 28 cm to 28 cm with the collimator at 90° and a full gantry rotation. The nominal dose rate was 800 MU/minute, and the maximum gantry rotation speed was 24°/sec. Institutional dosimetric constraints were used for optimization including a mean lung dose limit of less than 8 Gy. All the plans were normalized so that 85% the primary planning target volume received the prescription dose.

RESULTS

The average mean doses to the target volumes ranged from 12.2 to 12.6 Gy in the Halcyon TMLI plans, while they ranged from 12.1 to 12.5 Gy in the HT TMLI plans. Relative to the prescription dose, the average mean dose for normal organs ranged from 21.3% to 56.6% in the Halcyon TMLI plans, while it ranged from 10.1% to 68.4% in the clinical HT plans. The difference in the average mean dose to normal organs was less than 0.5 Gy except two organs between the Halcyon and HT TMLI plans. The average median dose for normal organs ranged from 18.2% to 48.8% relative to the prescription dose in the Halcyon TMLI plans. The mean lung dose (MLD) in the Halcyon TMLI plans met the institutional limit with an average dose of 6.75±0.42 Gy (range: 6.44 - 7.36 Gy), while the average MLD was 6.54±0.77 Gy (range: 6.24 - 7.22 Gy) in the HT plans (p-value = 0.71 in the paired t-test). The average total monitor unit in the Halcyon TMLI plans was 4,425±906 MU (range: 3,470 - 5,575 MU) with an average beam-on time of 5.1±1.3 minutes (range: 4.1 - 7.0 minutes), which excludes isocenter setup time, while the average beam-on time was 22.2±3.2 minutes (range: 19.6 - 26.1 minutes) with the HT plans.

CONCLUSION

Halcyon TMLI plans met our institutional dosimetric constraints with adequate normal organ sparing and target dose coverage. The beam-on time with the Halcyon plans was significantly shorter than that with the HT plans, which could lead to shorter treatment time and increased patient comfort. This study showed the feasibility of TMLI treatments on the Halcyon machine. The same method could be used for total body irradiation on Halcyon.

Evaluation of a Deep Image to Image Network (DI2IN) Auto-Segmentation Algorithm across a Network of Cancer Centers

PURPOSE/OBJECTIVE(S)

Due to manual OAR contouring challenges, various automatic contouring solutions have been introduced. Historically, common clinical auto-segmentation algorithms used were atlas based, which required maintaining a library of self-made contours. Searching the collection was computationally intensive and could take several minutes to complete. Deep learning approaches have shown significant benefits compared to atlas-based methods in improving segmentation accuracy and efficiency in auto-segmentation algorithms. This work represents the first multi-institutional study to describe and evaluate an AI algorithm for auto-segmentation of organs at risk (OARs) based on a deep image-to-image network (DI2IN).

MATERIALS/METHODS

The AI-Rad Companion Organs RT (AIRC) algorithm (Siemens Healthineers, Erlangen, Germany) uses a two-step approach for segmentation. In the first step, the target organ region in the optimal input image is extracted using a trained Deep Reinforcement Learning network (DRL), which is then used as input to create the contours in the second step based on DI2IN. The study was initially designed as a prospective single-center evaluation. The automated contours generated by AIRC were evaluated by three experienced board-certified radiation oncologists using a 4-point scale where 4 is clinically usable and 1 requires re-contouring. After seeing favorable results in a single-center pilot study, we decided to expand the study to 6 additional institutions, encompassing 8 additional evaluators for a total of 11 physician evaluators across 7 institutions.

RESULTS

One hundred fifty-six patients and 1366 contours were prospectively evaluated. The 5 most commonly contoured organs were the lung (136 contours, average rating = 4.0), spinal cord (106 contours, average rating = 3.1), eye globe (80 contours, average rating = 3.9), lens (77 contours, average rating = 3.9), and optic nerve (75 contours, average rating = 4.0). The average rating per evaluator per contour was 3.6. On average 124 contours were evaluated by each evaluator. 65% of the contours were rated as 4 and 31% were rated as 3. Only 4% of contours were rated as 1 or 2. 33 organs were evaluated in the study, with 19 structures having a 3.5 or above average rating (ribs, abdominopelvic cavity, skeleton, larynx, lung, aorta, brachial plexus, lens, eye globe, glottis, heart, parotid glands, bladder, kidneys, supraglottic larynx, submandibular glands, esophagus, optic nerve, oral cavity) and the remaining organs having a rating of 3.0 or greater (female breast, proximal femur, seminal vesicles, rectum, sternum, brainstem, prostate, brain, lips, mandible, liver, optic chiasm, spinal cord, spleen). No organ had an average rating below 3.

CONCLUSION

AIRC performed well with greater than 95% of contours accepted by treating physicians with no or minor edits. It supported a fully automated workflow with the potential for time savings and increased standardization with the use of AI-powered algorithms for high quality OAR contouring.

Using Scorecards to Tune Ethos Directive Templates: An ARTIA Cervix Dosimetric Planning Study

PURPOSE/OBJECTIVE(S)

The Adaptive Radiation Therapy Individualized Approach (ARTIA) Cervix clinical trial uses predefined clinical directive templates (CDT) combined with RapidPlan DVH estimations (DVHe) to guide plan optimization in the Ethos treatment planning system. The dosimetric scorecard tool (DST) quantifies improvements in plan quality. This is the first study to utilize the DST to tune an Ethos CDT to improve resulting plan quality.

MATERIALS/METHODS

Iterative replanning was used to modify the draft CDT (CDT-1) in Ethos to generate a new CDT (CDT-2) that maximized the clinical consensus scorecard's total score compared toCDT-1. CDT-2 was established, and resulting plans were compared with and without a DVHe. Additional fixed field IMRT beam geometries were compared between CDT-1 and CDT-2, both with DVHe. After obtaining favorable results when comparing CDT-1 verses CDT-2 for two test cases, 10 additional cases were retrospectively identified and tested.

RESULTS

For the initial test cases, CDT-2 decreased OAR doses without compromising PTV coverage (No DVHe). While both plans met the protocol target guidelines and OAR constraints, the scorecard was able to quantify the improvement with CDT-2 on a test case with a score of 166.1 (78.7%) vs CDT-1, 163.87 (77.6%). When CDT-2 was combined with the DVHe, it still marginally outperformed CDT-1: 168.73 (76%) versus 166.13 (74.8%). Plan quality was further improved by increasing the total number of fields to 19. Combining CDT-2 and DVHe with a 19-field geometry resulted in the greatest benefit at 184.6 (83.2%). This scored higher than the ARTIA-Cervix defined delivery technique of CDT-1 and DVHe, with a 9-field geometry 166.1 (74.8%). The study was expanded to a separate analysis on 10 new cases. The 19-field approach was superior for all 10 cases and CDT-2 achieved a higher score in 7/10 cases. When comparing 9 versus 19 fields, the total optimization and calculation time increased by an average of 1.9 minutes while the beam delivery time increased by an average of 2.8 minutes (+/- 0.1). The average MU/field was 174.3 (total 1568.3) and 129.9 (total 2468) for 9 and 19 fields, respectively. Two test plans were re-optimized and calculated with Ethos 1.1 maintenance release (MR) 1 with both 9 and 19 fields. For case 1, MR 1 resulted in an 8.4% and 6.9% decrease in MU and scored -0.6% and +0.5% for 9 and 19 fields, respectively. For case 2, MR 1 resulted in a 0.8% and 3.1% decrease in MU and scored -3.4% and -0.3% for 9 and 19 fields, respectively.

CONCLUSION

The scorecard allows for easy evaluation of the dosimetric impact of other planning parameters (beam arrangements and use of DVHe) to identify the best approach. Using a scorecard to finely-tune a CDT is expected to improve planning efficiency, decrease intra-institutional plan quality and variability, improve the average calculated plan quality and benefit CBCT-guided ART.

Pelvic Nodal Auto-Segmentation Using a Deep Image to Image Network (DI2IN) Auto-Segmentation Algorithm: Comparing Male vs. Female Pelvis

PURPOSE/OBJECTIVE(S)

Deep Learning approaches have shown significant benefits compared to atlas-based methods in improving segmentation accuracy and efficiency in auto-segmentation algorithms. The AI-Rad Companion Organs RT pelvic nodal auto-segmentation feature was trained and developed for use in the male pelvis. There is no real-world data on its usability in male pelvis and whether it can be used for female pelvic nodal anatomy. This work represents the first multi-institutional study to describe and evaluate an AI algorithm for auto-segmentation of the pelvic nodal region in female patients based on a deep image-to-image network (DI2IN).

MATERIALS/METHODS

The AIRC algorithm uses a two-step approach for segmentation. In the first step, the target organ region in the optimal input image is extracted using a trained Deep Reinforcement Learning network (DRL), which is then used as input to create the contours in the second step based on DI2IN. We retrospectively evaluated AIRC pelvic nodal auto-segmentation in both male and female patients treated at our network of institutions. The automated pelvic nodal contours generated by AIRC were evaluated by one board-certified radiation oncologist, specializing in prostate and gynecologic malignancies. A 4-point scale was used, where 4 is clinically usable and 1 requires re-contouring. Pelvic nodal regions included the right and left side of the common iliac, external iliac, internal iliac, obturator and midline presacral nodes. A chi-squared test was then used to compare the scores of male and female pelvic nodal cases.

RESULTS

Fifty-two female and 51 male patients were included in the study, representing a total of 468 and 447 pelvic nodal regions, respectively. 96% (450 pelvic nodal contours) and 99% (443 pelvic nodal contours) required no or minor edits for female and male patients, respectively (p = 0.004). The right internal iliac was the only nodal group with a statistically significant difference between female (92% requiring no or minor edits) and male (100% requiring no or minimal edits) patients, p = 0.04. The percentage of patients requiring no, or minor edits was 87% (45 patients) and 92% (47 patients) for female and male patients, respectively (p = 0.36).

CONCLUSION

AIRC pelvic nodal auto-segmentation performed very well in both male and female pelvic nodal regions, with the male pelvic nodal regions performing better especially in the right internal iliac nodal group. It is usable in female pelvic nodal regions, with 96% of contours requiring no or minor edits. As auto-segmentation becomes more widespread, it may be important to have equal representation from all genders in training and validation of auto-segmentation algorithms.

Pilot Study of Peer Review in Low Middle-Income Country (LMIC) through Cloud-Based Platform

PURPOSE/OBJECTIVE(S)

Peer review is an essential step in clinical quality assurance and can impact patient safety and treatment outcomes. Most published data on peer review is from developed nations, with little data on peer review from low middle income countries (LMIC). Major challenges to peer review can include a lack of time, expertise and commitment from team members. With increasing access to advanced technology in LMIC, peer review is becoming more important to maintain quality and standard of care. We evaluated cloud-based e- peer review (Varian) in our network of hospitals in India with an aim to see feasibility and impact on care.

MATERIALS/METHODS

Four of 15 centers across India were selected for this pilot study. All team members were trained on the platform prior to implementation. New cases for the week treated with definitive intent were selected by the dosimetrist. The link to the cases were sent through email to reviewing physicians. Various aspects which were reviewed for each case were.1) Work up & staging (Documents were scanned and loaded).2) Treatment intent & prescription.3) Target contours.4) Normal Organ at risk contours.5) Dose- Volume -Histogram (DVH) with clinical goals attached. Cases were marked as "Not Appropriate", "Appropriate", "Appropriate with minor finding", "Represent with major revisions" as per volume and plan review.

RESULTS

Over a period of 2 months, a total of 80 cases underwent e-Peer Review at our network of hospitals prior to the start of treatment. Median turnover time (like from link sent to time to completion of review) was 48 (6-360) hours. Mean time taken by physician for review was 9 minutes (range 3 to15). 31.2% of cases were accepted without any changes, 51.9 % had a minor change and 16.9 % cases had major changes. Most frequent reason of major changes was contouring corrections 16.9%. 31% of major changes underwent recontouring and replanning before initiation of treatment.

CONCLUSION

Peer review was feasible in our network through this e-peer review system, with average turnover time and mean time taken for review of 48 hours & 9 min respectively. Peer review led to significant changes which could impact patient care delivery and outcome. The ability to review cases asynchronously via this cloud-based e-peer review system, helped to ease the burden of scheduling between treating and reviewing physician. We plan to implement this across the remaining centers in our network.

Physician-driven artificial intelligence enabled planning for intraprostatic dose escalation in under ten minutes

187

Background: Intraprostatic radiation dose escalation is an area of clinical interest. Dose escalation within the prostate must be balanced with maintaining acceptable dose to the organs at risk, OAR (bladder, rectum, and urethra). Treatment planning therefore requires simultaneous consideration of multiple competing plan optimization goals, for which iterative, interdisciplinary treatment planning tasks may take significant physician, physicist, and dosimetrist time. Semi-automated treatment planning using artificial intelligence has the potential to significantly reduce treatment planning time for technically complex treatments. Methods: A prostate SBRT planning template was created using the Varian ETHOS treatment planning system (TPS) combined with an in-house RapidPlan SBRT prostate model. Prostate dose was prescribed to 36.25 Gy over 5 fractions with 95% coverage to the PTV. To respect standard SBRT normal tissue toxicity constraints while simultaneously escalating intraprostatic dose, the TPS automatically created an intraprostatic boost structure (PTV_SIB), derived from the PTV by excluding OARs with a pre-determined margin. Physicians were trained to perform treatment planning using the prostate SBRT planning template. Treatment planning was performed on 5 unique patients. The time spent from initiation to end of treatment planning and dosimetric parameters were recorded. Results: For each patient, the ETHOS TPS generated two SBRT plans (9 field static IMRT and 3 VMAT arc) with intraprostatic dose escalation in an average of 9.3 minutes [range 8.4-11.8]. Static field and VMAT plans were comparable. PTV_SIB was escalated to above 50 Gy in all cases. Relevant dosimetry for each patient’s static IMRT plan is shown. Conclusions: Physician-driven ETHOS treatment planning was able to produce boosted internal PTV doses using autosegmented volumes. The ETHOS TPS was able to generate dose-escalated plans that reconciled complex OAR and PTV goals within 8-12 minutes. Hence, the ETHOS TPS opens the possibility of rapid physician-driven treatment planning throughput. [Table: see text]

A Grading System for the Assessment of Risk of Extraprostatic Extension of Prostate Cancer at Multiparametric MRI

Purpose To evaluate MRI features associated with pathologically defined extraprostatic extension (EPE) of prostate cancer and to propose an MRI grading system for pathologic EPE. Materials and Methods In this prospective study, consecutive male study participants underwent preoperative 3.0-T MRI from June 2007 to March 2017 followed by robotic-assisted laparoscopic radical prostatectomy. An MRI-based EPE grading system was defined as follows: curvilinear contact length of 1.5 cm or capsular bulge and irregularity were grade 1, both features were grade 2, and frank capsular breach were grade 3. Multivariable logistic regression and decision curve analyses were performed to compare the MRI grade model and clinical parameters (prostate-specific antigen, Gleason score) for pathologic EPE prediction by using the area under the receiver operating characteristic curve (AUC) value. Results Among 553 study participants, the mean age was 60 years ± 8 (standard deviation); the median prostate-specific antigen value was 6.3 ng/mL. A total of 125 of 553 (22%) participants had pathologic EPE at radical prostatectomy. Detection of pathologic EPE, defined as number of pathologic EPEs divided by number of participants with individual MRI features, was as follows: curvilinear contact length, 88 of 208 (42%); capsular bulge and irregularity, 78 of 175 (45%); and EPE visible at MRI, 37 of 56 (66%). For MRI, grades 1, 2, and 3 for detection of pathologic EPE were 18 of 74 (24%), 39 of 102 (38%), and 37 of 56 (66%), respectively. Clinical features plus the MRI-based EPE grading system (prostate-specific antigen, International Society of Urological Pathology stage, MRI grade) predicted pathologic EPE better than did MRI grade alone (AUC, 0.81 vs 0.77, respectively; P < .001). Conclusion Higher MRI-based extraprostatic extension (EPE) grading categories were associated with a greater risk of pathologic EPE. Clinical features plus MRI grading had the highest diagnostic performance for prediction of pathologic EPE. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Eberhardt in this issue.

The disappearing PI-RADS 5 prostate lesion

Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) identifies prostate cancer on the basis of multiparametric MRI (mpMRI). As an assessment tool, it correctly predicts clinically significant cancer in the vast majority of cases. In this light, we report a rare patient, for whom a PI-RADS 5 lesion vanished over the course of 13 months.

Active surveillance of prostate cancer in African-Americans during the MRI era

108

Background: Many patients with low-risk prostate cancer are encouraged by their physicians to pursue active surveillance (AS). AS has increasingly been utilized, however there remains anxiety by patients and their physicians that more aggressive disease will be missed and allowed to progress. African-American (AA) patients may present with more aggressive disease and higher rates of upgrading at the time of radical prostatectomy. Due to these factors, physicians may be hesitant to recommend AS to AA patients. We examined the role of AS in these patients in the era of MRI targeted biopsies. Methods: A prospectively maintained database was queried for all patients who underwent an MRI guided fusion biopsy from 2007 to 2016 and chose AS as their primary management strategy. Patents with Gleason Group (GG) 1 or 2 were eligible. Patients were then followed with yearly PSA, exam, MRI and biopsy if warranted. MRI Fusion biopsies were reviewed to determine any GG progression. Results: A total of 19 AA and 143 non-AA patients were reviewed with median follow up times of 31.63 (15.42 -89.50) and 30.87 (3.45 – 99.85) months, respectively. AA and non-AA patients had similar baseline PSA values (6.08 ± 2.93 vs. 5.89 ± 4.23, p = 0.85), proportion of GG 1 (15.89% vs 21.68%, p = 0.55) and PSA density (0.103 ± 0.041 vs. 0.123 ± 0.041, p = 0.36. However, AA patients did present at an earlier age (58.89 ± 6.64 vs. 63.69 ± 6.64, p = 0.004). A total of 8/19 (42.1%) AA and 46/143 (32.2%) non-AA had GG upgrading while on AS, p = 0.34. The median time until progression for AA and non-AA patients was 60.76 and 77.42 months, p = 0.68. Conclusions: In our study, AA men did begin AS at an earlier age than non-AA men. While both groups had statistically similar rates of progression, the relative risk of progression was higher in the AA cohort during this time period. Therefore, in the era of MRI and fusion biopsies we are better able to detect upgrading and somewhat mitigate the the risks associated with upgrading during AS irrespective of race but larger studies are needed to determine whether there are meaningful differences in the rates of progression between AA and non-AA men. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH.

Prediction of adverse pathology after radical prostatectomy on MPMRI in the PIRADS v2 era

121

Background: As the use of MRI in the diagnosis of prostate cancer (PCa) becomes more established, knowledge of its utility as a prognostic tool is needed to better counsel patients. Here, we aim to assess the ability of mpMRI to predict adverse pathologic factors, such as extraprostatic extension (EPE), seminal vesicle invasion (SVI) or lymph node involvement (LNI) on final pathology after radical prostatectomy (RP). Methods: A prospectively maintained database was queried for all men who underwent mpMRI with current PI-RADS v2 scoring system, MRI/TRUS fusion biopsy (FBx), and RP at our institution (n = 112). Patient demographics, clinical data, imaging and pathology were recorded. Patients were stratified by presence of adverse pathology (AP), defined as EPE, SVI or LNI. Statistical analyses were used to identify mpMRI characteristics predictive of AP using STATA 13. Results: Patients with adverse pathology were middle aged, predominantly caucasian, and significantly higher PSA at baseline (Table 1). Having a PI-RADS 5 lesion was positively associated with AP (adjusted OR = 4.37, 95% CI = 1.20-15.87, p = 0.02). Mean lesion diameter on mpMRI was greater in patients with AP (p < 0.01). However, number of lesions (p = 0.12) and prostate volume on mpMRI (p = 0.88) were not associated with AP. Conclusions: The results of this study demonstrate that features on mpMRI, particularly a PI-RADS score of 5 and large lesion diameter, are predictive of adverse pathology. This information will prove valuable in developing an imaging-based prognostic model in the era of MRI and FBx. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH and NIH Medical Research Scholars Program[Table: see text]

Ability of multiparametric magnetic resonance imaging (MRI) to predict prostate tumor heterogeneity on targeted biopsy

113

Background: Prostate cancer (PCa) can show heterogeneous histology within lesions. MRI-targeted biopsy (Tbx) of the prostate improves PCa detection, but sampling within lesions has yet to be standardized. Furthermore, Tbx results are often heterogeneous as evidenced by differing histologic grades of Tbx cores within the same lesion. This introduces potential variability in biopsy results, on which clinical decisions are made. Here we aim to characterize lesion heterogeneity and identify predictive multiparametric MRI (mpMRI) features. Methods: A cohort of men who underwent mpMRI and Tbx between 2014-2017 were selected for analysis from a prospectively maintained database. To characterize lesion heterogeneity, only men with ≥2 positive Tbx cores were included. Histologic grades were scored according to International Society of Urological Pathology (ISUP) grades. Lesion heterogeneity, reported as a heterogeneity index (HI), was calculated as the difference of the average ISUP grades of Tbx cores per lesion from the maximum sampled ISUP grade of that lesion. Statistical analyses identified associations between imaging features and lesion heterogeneity. Results: 157 lesions in 114 patients met inclusion criteria. Maximum ISUP grade ranged from 1 to 5, with a median ISUP grade of 2. Higher ISUP grades were associated with greater lesion heterogeneity, HI for ISUP grade ≥3 = 0.58±0.11 vs <3 = 0.29±0.08, p = 0.0001. In addition, increasing lesion size on mpMRI was associated with greater lesion heterogeneity, HI for ≥2cm = 0.52±0.14 vs <2cm = 0.32±0.08, p = 0.0096. Finally, higher mpMRI suspicion scores were associated with increased heterogeneity vs lower suspicion scores, p = 0.048. Conclusions: mpMRI aids in characterizing PCa lesion heterogeneity to predict variability of histologic grades on Tbx. This information can assist Tbx planning to potentially reduce risks of upgrading on final pathology. Future research will examine how lesion heterogeneity can impact risk stratification and clinical decision-making for patients and practitioners. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH and NIH Medical Research Scholars Program.

Are all biopsies created equal? comparison of extended sextant prostate biopsies performed with and without MRI-TRUS fusion biopsy system

117

Background: Extended sextant systematic prostate biopsies have the inherent risk of under-sampling prostate cancer. Fusion guided multiparametric magnetic resonance imaging (mpMRI) biopsies have been employed to better represent the disease and guide treatment. We sought to determine if due to heightened suspicion of cancer and/or visualization of mpMRI there were any discrepancies between systematic biopsies done with a Fusion System as compared to those done without (TRUS alone). Methods: From a prospectively collected database, we performed a review collecting age, race, clinical stage, PSA, and time until repeat systematic biopsy as part of fusion guided biopsy (IB). We also collected pathology results reported as Gleason Score (GS), for both the patients’ OB and our IB. Patients were stratified into groups based on time between OB and IB/fusion biopsy ( < 6 months, < 1 year and < 2 years). Results: 69 patients with a previous OB underwent combined fusion and IB within our designated time intervals. Cancer detection rates between the OB and IB results were similar at 6 months, 1 year and 2 years (80 vs 90%, 87.5 vs 87.5% and 65 vs 69%). Detection rates of GS ≥ 3+4 were higher with IB within 12 months compared with IB from 12-24 months (72.7 vs 40.9%, p = 0.03 OR 3.85 (1.09-13.66). Of the patients who were upgraded (n = 24), 54.2% (n = 13) went from benign pathology to a diagnosis of prostate adenocarcinoma. Of all OB GS 3+3 (n = 31), 29% were restaged to higher risk disease on IB. Rates of IB upgrading were similar within 6 months, 1 year and 2 year, 40%, 33.33% and 31.91%). Patients who were upgraded on IB compared to those who were not upgraded were of similar age (67.0 ± 6.53 vs 66.50 ± 6.47), race (17.4% African-American vs 13%), PSA (7.60 ± 5.61 vs 7.50 ± 4.39) and prostate volume on MRI (51.30 ± 26.87 vs 59.26 ± 38.52). Conclusions: A systematic biopsy at our referral center during a mpMRI fusion biopsy was over 3.5 times more likely to detect GS ≥ 3+4 when done within 1 year of the outside biopsy. There continued to be a risk, 34.7% overall, of disease upgrading in all time periods. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH

Long-term follow-up of clinical presentation and outcomes of patients with urinary bladder paragangliomas

507

Background: Urinary bladder paragangliomas (UBPGLs) are extremely rare, accounting for less than 6% of paragangliomas (PGLs) and 0.06% of bladder tumors. The goal of this study is to examine the presentation, clinical characteristics and outcomes of patients with UBPGLs. Methods: We determined the presenting symptoms, clinical characteristics, and outcomes of patients who presented to a single institution with UBPGLs from 2000-2017. Results: 28 patients with an average age of 27 ± 15.6 at symptom onset presented to the NIH from 2000-2017. The majority had standard paraganglioma symptoms (n = 24, 85.7%) defined as headaches, palpitations, pallor and anxiety, and hypertension (n = 20, 71.4%) on presentation. 8 patients (29%) presented with hematuria; hematuria was the only presenting symptom in 1 of these patients. 3 (10.7%) of the patients were completely asymptomatic and were discovered to have bladder paragangliomas incidentally on imaging. Overall, 9 patients (32%) were under 18 (average age = 10.9 ± 3.9) at symptom onset. 14 (50%) patients developed metastasis, with bone (n = 9) and lung (n = 8) being the most common metastatic sites. All but 1 patient received surgical treatment, with 6 patients receiving transurethral resection of bladder tumor (TURBT), 3 receiving robotic-assisted partial cystectomy (RAPC) and the remaining patients undergoing open cystectomy. In total, 2 patients experienced bladder cancer recurrence, both of whom had undergone TURBT. Comparing patients with and without hematuria, metastasis and standard paraganglioma symptoms, we found no statistically significant difference in mean diameter of the largest lesion or plasma catecholamine values. Conclusions: Our experience reveals that most patients with UBPGLs present at an early age with characteristic paraganglioma symptoms. Despite the variety of surgical methods used to manage these patients, the only 2 recurrences were in patients who underwent TURBT. Further work is necessary to establish preoperative indicators of disease severity in patients with UBPGLs. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH and NIH Medical Research Scholars Program

Active surveillance criteria in the age of targeted biopsies

116

Background: Many urologists are now using active surveillance (AS) to manage patients with low-risk prostate cancer. A variety of criteria have been proposed to select patients for AS. A key feature of these criteria is Gleason Group as determined by systematic or “random” biopsies (SB). In this study, we examined the progression of Gleason Group (GG) detected only on SB compared to patients with positive MRI-fusion or “targeted” biopsies (FB). Methods: A prospectively maintained database was queried for all patients who underwent an MRI guided FB and SB from 2007 to 2016 and chose AS as their primary management strategy. Patents with GG 1 or 2 were eligible. Patients were then followed with yearly PSA, exam, MRI and biopsy if warranted. FBs were reviewed to determine GG progression. We divided patients into those who had cancer detected on SB only and those who had positive FBs with or without a positive SB. Results: A total of 162 patients met our criteria with 73 having an initial positive FB and 89 having cancer only on SB and a negative FB. Median follow-up was 27.62 (4.14 – 96.56) and 33.83 (3.45-99.84) months, respectively. The two groups were similar in age (64.49 ± 6.57 vs. 62.08 ± 6.92 years, p = 0.03) and PSA (6.23 ± 4.23 vs. 5.67 ± 3.98 ng/ml, p = 0.39). The median time to pathologic progression for GG 1 patients with initial FB positive was 53.88 months and those with GG 1 on initial SB was 80.81 months (p = 0.003). The median time to pathologic progression for GG 2 patients with initial FB positive was 36.26 months and those with GG 2 on initial SB was 76.01 months (p = 0.099). Conclusions: Previously accepted AS criteria have been based on SBs. However, those patients placed on AS after a positive FB progressed fast than cancer detected only on SB. With MRI and FBs more routinely used in clinical practice, clinicians could use this information from FBs to better stratify and closely monitor patients during AS. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH.

Is BMI a risk factor for active surveillance progression in patients with prostate cancer diagnosed by MRI-Trus fusion biopsy?

124

Background: MRI−TRUS fusion biopsy (FBx) use in the diagnosis of prostate cancer (PCa) results in a more accurate assessment of disease burden and has increasingly been incorporated into urologic practice. In addition, with more men choosing active surveillance (AS) and the reports of increased PCa aggressiveness with obesity, we wanted to study the impact of obesity on the risk of PCa progression in men on AS diagnosed and followed by MRI and MRI−TRUS FBx. Methods: A retrospective review was performed on a prospectively maintained database of all men who underwent MRI−TRUS FBx at our institution from January 2007 to May 2015. Patient demographics, clinical data, imaging, pathology, treatment and outcomes were recorded. Patients who enrolled on AS were stratified by BMI into normal weight (BMI 18.5−24.9), overweight (BMI 25.0−29.9), and obese (BMI ≥ 30.0). Statistical analysis was performed using SPSS software. Results: 204 men were enrolled in AS. Within the AS cohort, 51 (25%) had a normal weight, 101 (49.5%) were overweight, and 52 (25.5%) were obese. Age, BMI, PSA and mean estimated progression free survival time are described for each of these groups in Table 1. The overall rate of progression was 32.8%. Of the patients who progressed, 18 (26.9%) were normal weight, 32 (15.7%) were overweight and 17 (25.4%) were obese. On multivariate analysis, BMI was not a risk factor for AS progression, HR = 1.00 (p = 0.99, 95% CI = 0.95−1.06). Conclusions: There is evidence of increased risk of aggressive PCa specific death in obese patients. However, we demonstrate that in patients diagnosed by FBx, obesity does not confer an additional risk of progression on AS. This may be due to the improved characterization of cancer volume and grade by MRI−TRUS fusion biopsy. Further study is required to determine risk factors for AS progression in patients undergoing FBx. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH, Medical Research Scholars Program.

Characterization of urinary bladder paragangliomas in patients with germline mutations

508

Background: Data on the genetic characteristics of patients with urinary bladder paragangliomas (UBPGLs) is extremely limited. The primary goal of this study is to examine the clinical characteristics of a series of patients with UBPGLs, focusing particularly on their genetic profiles. Methods: We analyzed the medical records of patients who presented with UBPGLs from 2000 to 2017 to determine their presenting symptoms, clinical characteristics and outcomes. In addition, patients were stratified by the presence or absence of metastasis and the presence or absence of multiple paragangliomas (PGLs). Groups were compared using chi-square test and t-test (Stata) statistical analyses. Results: 18 of the 28 patients (64.2%) with UBPGLs had underlying genetic mutations: 15 (53.5%) in the succinate dehydrogenase subunit B gene (SDHB) and 3 (10.7%) in the von Hippel-Lindau gene (VHL). The average age at first symptoms was significantly younger in patients with germline mutations compared to those without mutations (22.3 ± 2.52 vs 37.3 ± 5.95, p = 0.01). 7 patients (38.9%) with germline mutations developed metastasis, at either first presentation or on follow-up, compared to 7 patients (70%) without germline mutations, p = 0.15. 10 patients (58.8%) with germline mutations had multiple PGLs compared to 1 patient (11.1%) without germline mutations, p = 0.02. On average, patients with germline mutations had larger lesions than patients without germline mutations based on the means of the largest diameter (3.7 ± 2.6 vs 3.1 ± 2.2, p = 0.51). Conclusions: Patients presenting with UBPGLs should be screened for underlying germline mutations as they are frequently associated. Patients with UBPGLs and underlying germline mutations present at a significantly younger age than patients without these mutations. Even though patients with UBPGLs and underlying mutations are significantly more likely to develop multiple PGLs, the risk of metastasis is not greater compared to patients without germline mutations. Therefore, all patients with UBPGLs should be followed closely for metastatic development. This research was supported by the Intramural Research Program of the National Cancer Institute, NIH and NIH Medical Research Scholars Program.