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Purpose On June 13 to 14, 2019, the American Society for Radiation Oncology and the Radiological Society of North America convened a workshop on the treatment of oligometastatic disease in Washington, DC. The workshop was initiated for several reasons. First, oligometastatic disease is of increasing academic and community interest and has been identified by the American Society for Radiation Oncology membership as a top research priority. Second, emerging imaging and diagnostic technologies are more readily defining and detecting oligometastatic disease, making contemporary discussion of oligometastatic disease especially relevant. Third, radiosurgery and radiation in general are theorized to be ideal noninvasive therapy for the treatment of oligometastatic disease. Finally, innovations in targeted therapy and immune therapy have the potential to reverse widely disseminating disease into an oligometastatic state. Methods and Materials The workshop was organized into 2 keynote addresses, 6 scientific sessions, and 3 group discussions during an end-of-workshop breakout session. New scientific work was presented in the form of 4 oral presentations and a poster session. Workshop participants were charged with attempting to answer 3 critical questions: (1) Can we refine the clinical and biological definitions of oligometastatic disease; (2) how can we better treat oligometastatic disease; and (3) what clinical trials are needed? Results Here, we present the proceedings of the workshop. Conclusions The clinical implications of improved treatment of oligometastatic disease are enormous and immediate. Radiation oncology and diagnostic radiology should rightly be at the forefront of the characterization and treatment of oligometastatic disease. Focused effort is required so that we can translate current efforts of large numbers of studies with few patients to larger studies of larger impact.

Purpose High-dose-rate (HDR) brachytherapy is an effective method of treating localized prostate cancer. There are limited data on the relationship between implant interval and outcomes. This study aims to assess if the implant interval between HDR treatments has an impact on patient-reported health-related quality of life (QOL) and physician-graded toxicity in men treated for localized prostate cancer. Material and methods Patients were treated with HDR brachytherapy as monotherapy with 27 Gy in 2 fractions, given over two implants, performed 1-2 weeks apart. Patients were dichotomized into one-week and two-week cohorts. Patient-reported EPIC-26 genitourinary (GU), gastrointestinal (GI), and sexual QOL were assessed. Linear regression, chi-squared testing, and generalized linear mixed effect models were used to assess the differences in patient characteristics, patient-reported QOL, and physician-graded toxicity. Results Outcomes of 122 patients were analyzed. Median follow-up was 18 months. Patient-reported GU and GI QOL worsened after treatment with a return towards baseline over time, while patient-reported sexual QOL worsened after treatment, but did not return towards baseline. There were no differences in patient-reported health related QOL as a function of implant interval. Maximum physician-graded GU, GI, and sexual toxicity rates of grade 2 or 3 were 68%, 3%, and 53%, respectively. There was no difference in rates of grade 2 or 3 toxicity as a function of implants interval. Conclusions HDR brachytherapy for prostate cancer is a well-tolerated treatment. The interval between treatments is not associated with differences in patient-reported QOL or physician-graded toxicities.

Background Fiducial markers are frequently used before treatment for image‐guided patient setup in radiation therapy (RT), but can also be used during treatment for image‐guided intrafraction motion detection. This report describes our implementation of automatic marker detection with periodic kV imaging (TrueBeam v2.5) to monitor and correct intrafraction motion during prostate RT. Methods We evaluated the reproducibility and accuracy of software fiducial detection using a phantom with 3 implanted fiducial markers. Clinical implementation for patients with intraprostatic fiducials receiving volumetric modulated arc therapy (VMAT) utilized periodic on‐board kV imaging with 10 s intervals during treatment delivery. For each image, the software automatically identified fiducial locations and determined whether their distance relative to planned locations were within a 3 mm tolerance. Motion was corrected if either ≥2 fiducials in a single image or ≥1 fiducial in sequential images were out of tolerance. Results Phantom studies demonstrated poorer performance of linear fiducials compared to collapsible fiducials, and wide variability to accurately detect fiducials across eight software settings. For any given setting, results were relatively reproducible and precise to ~0.5 mm. Across 17 patients treated with a median of 20 fractions, the software recommended a shift in 44% of fractions, and a shift was actually implemented after visual confirmation of movement greater than the 3 mm threshold in 20% of fractions. Adjustment of our approach led to improved accuracy for the latter (n = 7) patient subset. On average, table repositioning added 3.0 ± 0.3 min to patient time on table. Periodic kV imaging increased skin dose by an estimated 1 cGy per treatment arc. Conclusions Periodic kV imaging with automatic detection of motion during VMAT prostate treatments is commercially available, and can be successfully implemented to mitigate effects of intrafraction motion with careful attention to software settings.

BACKGROUND: As exemplified in patients with adenoid cystic carcinoma (ACC), metastatic salivary gland cancers display heterogenous behavior. Although anatomic site of metastasis has been suggested to be prognostic for survival in this population, this is not adequately characterized in the current literature. METHODS: Using the National Cancer Database (NCDB), patients with newly diagnosed metastatic salivary gland cancers with distant metastasis to a single organ were identified. RESULTS: Eight hundred and fifty-eight patients (n = 284 bone-only, n = 322 lung-only, n = 252 other-site-only) were identified. Anatomic site of distant metastasis was not associated with survival in the cohort as a whole; however, on pre-planned subgroup analysis, lung-only metastasis, relative to bone-only metastasis, was the only factor associated with improved survival in patients with ACC (HR: 0.52, 95%CI: 0.30-0.93, p = 0.029). CONCLUSIONS: Anatomic site of metastasis is strongly associated with survival in patients with metastatic ACC and should be considered in future studies aiming to optimize therapy in this population.

OBJECTIVES Our understanding of odontogenic cancers is limited primarily to case studies given the rarity of these head and neck neoplasms. Using the National Cancer Database, we report the treatment patterns and survival outcomes for one of the largest cohorts of patients with odontogenic cancers. METHODS Patients with odontogenic tumors who did not have metastatic disease and received at least part of their care at the reporting facility were included. Patient and treatment variables were assessed using logistic regression. Survival was assessed using Cox proportional hazard models. RESULTS We identified 437 patients with odontogenic cancers, the majority of which had malignant ameloblastoma (n = 203) or odontogenic carcinoma (n = 217). Median follow-up was 44.8 months. On multivariate analysis, improved survival was associated with age

Purpose Combining immune checkpoint blockade (ICB) with stereotactic body radiation therapy (SBRT) may improve the local response to radiation and the systemic response to immunotherapy. However, no prognostic markers exist to identify patients likely to benefit from combined therapy. The degree of T cell–mediated immunity, which can be quantified with radiomics using computed tomography (CT) imaging, is predictive of immunotherapy response. Herein we investigated whether a validated T cell radiomics score (RS) is correlated with clinical outcomes after multisite SBRT and pembrolizumab (SBRT + P). Methods and Materials The RS was quantified for 68 patients with metastatic treatment-refractory adult solid tumors who received SBRT (30-50 Gy, 3-5 fractions) and pembrolizumab ≤7 days after SBRT. RS was calculated using 8 variables, including 5 radiomics features extracted from pretreatment CT scans. At a prespecified cutoff of the 25th percentile, we assessed the association between RS and clinical outcomes. The Kaplan-Meier method was used to estimate survival outcomes. The prognostic effect of RS was assessed via logistic regression or Cox proportional hazards models. In an exploratory analysis, RS was also analyzed as a continuous variable. Results One hundred thirty-nine tumors were analyzed. At the 25th percentile cutoff, high-RS patients were more likely to exhibit irradiated tumor responses to SBRT + P (odds ratio [OR] 10.2; 95% confidence interval [CI], 1.76-59.17; P = .012). High-RS was associated with improved TMC compared with low-RS tumors (hazard ratio [HR] 0.18; 95% CI, 0.04-0.74; P = .018). Furthermore, high-RS patients had improved PFS (HR 0.47, 95% CI, 0.26-0.85; P = .013) and OS (HR 0.39, 95% CI, 0.20-0.75; P = .005). As a continuous variable, higher RS was associated with improved PFS (HR 0.12, 95% CI, 0.03-0.51; P = .004) but did not reach statistical significance for TMC (HR 0.36, 95% CI, 0.02-7.02; P = .502) or OS (HR 0.28, 95% CI, 0.05-1.55; P = .144). Conclusions We demonstrated the clinical validity of RS (at the 25th percentile cutoff) as a prognostic biomarker in patients treated with SBRT + P. Future validation of the prognostic value of RS in larger similarly treated patient cohorts is warranted.

Purpose/Objective(s) Stereotactic body radiotherapy (SBRT) is associated with high rates of metastasis control. However, given the adjacent organs-at-risk (OAR) and observed high rates of airway toxicity in the past, SBRT has historically not been routinely utilized for metastatic mediastinal and hilar lymphadenopathy (MHL). Immunotherapy is increasingly being used in metastatic patients and can cause clinically significant pneumonitis. In order to evaluate the feasibility, safety and efficacy of SBRT to MHL in the setting of immunotherapy, clinical outcomes of patients treated with immune-oncology (IO) agents and SBRT to MHL on three consecutive phase 1 clinical trials at a single institution were reviewed. Materials/Methods A total of 213 patients with widely metastatic solid tumors were treated with combination multisite SBRT and IO on three consecutive phase 1 trials between 2016 and 2020. All metastases in each patient were not irradiated and metastases > 65 mL were partially irradiated. Those with mediastinal and hilar nodes targeted met eligibility criteria. MHL were prescribed 50 Gy in 5 fractions, but under coverage was allowed in order to prioritize meeting OAR constraints formulated from NRG protocols. IO was administered sequentially (within 7 days after completion of SBRT) or concurrently (before or at the start of SBRT). IO treatments included: pembrolizumab, ipilimumab with nivolumab, urelumab with nivolumab, and cabiralizumab with nivolumab. Endpoints included irradiated tumor control per Response Evaluation Criteria in Solid Tumors version 1.1, overall survival (OS), dosimetric coverage and toxicity per Common Terminology Criteria for Adverse Events version 4.0. The Kaplan-Meier method was used to estimate tumor control and OS. Results A total of 55 patients were treated to 89 MHL nodes with 18 patients receiving concurrent IO and 37 patients receiving sequential IO. The most common histologies included non-small cell lung cancer (49%), ovarian cancer (7%) and colon adenocarcinoma (5%). Median follow up was 15 months. Irradiated tumor control was excellent with 0 local failures (# of living patients) at 12 (n = 32), 18 (n = 19) and 24 (n = 13) months. Median OS was 18 months (95% confidence interval, 11-33). Even after prioritizing OAR sparing, dosimetric parameters for the gross tumor volume (GTV) were: mean dose 50.9 Gy, V95 82% and V100 75%. Regarding toxicity, 6 patients (11%) experienced grade 3 pneumonitis and 1 patient (2%) experienced grade 3 esophagitis with no grade 4 or 5 toxicity events. Conclusion In the largest series of SBRT and immunotherapy for MHL, irradiated tumor control was excellent with acceptable toxicity. By prioritizing OARs during SBRT planning, 50 Gy/5 fraction SBRT to mediastinal and hilar nodes is feasible in the setting of immunotherapy.

Purpose/Objective(s) This study characterizes the efficacy and safety of stereotactic body radiation therapy (SBRT) with immunotherapy in the treatment of abdominal and pelvic lymph node metastases, based on a pooled analysis of three prospective phase I trials. While SBRT is frequently utilized for metastases, its role in the treatment of abdominal and pelvic lymphadenopathy remains unclear. We hypothesize that local control will remain excellent for nodal SBRT, even with prioritization of organ-at-risk (OAR) constraints resulting in undercoverage of target metastases and with omission of elective treatment of regional nodal basins. Materials/Methods Patients with widely metastatic solid malignancies were enrolled on three Phase I trials between 2016 and 2020 (total 213 patients). Patients were treated with multisite SBRT (up to 4 sites). Metastases > 65cc were partially treated. Immunotherapy was administered either concurrently or sequentially. Immunotherapy regimens included pembrolizumab, ipilimumab with nivolumab, urelumab with nivolumab, or cabiralizumab with nivolumab. The study cohort included patients who underwent SBRT to at least one lymph node in the abdomen or pelvis, including the inguinal regions. Local control (LC) of irradiated metastases and regional control (RC) of the corresponding nodal basin were determined per RECIST 1.1 guidelines. Overall survival (OS) was calculated using the Kaplan-Meier method. For each irradiated lesion, the mean dose, V95%, and V100% to the ITV and PTV were recorded. Results A total of 39 patients (mean age 59.2 years) underwent SBRT to 56 abdominal or pelvic lymph node metastases with median follow-up of 16.2 months. The median prescription dose was 45 Gy in 3 fractions. Median lesion volume was 17.0cc. Lymph node sites included 24 para-aortic/retroperitoneal (43%), 9 pelvic (16%), 11 inguinal (20%), 10 gastrohepatic/porta hepatis (18%), and 2 other (4%). Across all patients, the 1-year LC was 90.4%. Even without elective treatment of the corresponding nodal basins, 1-year RC was 81.9% (with only one isolated regional failure without concomitant distant progression). Median OS was 25 months, while 1-year and 2-year OS were 69.9% and 53.2%, respectively. ITV mean dose, V95%, and V100% were 47.3 Gy, 95.3%, and 89.5%, respectively (reported as medians across all 56 metastases). PTV mean dose, V95%, and V100% were 45.5 Gy, 84.2%, and 75.0%, respectively. The overall incidence of grade 3+ toxicity was 10.3%. The incidence of grade 3 colitis was 2.6% and grade 3 hepatitis was 2.6%, with no grade 4-5 colitis/hepatitis events. Conclusion In this pooled analysis of three prospective trials, SBRT to abdominal or pelvic lymph node metastases with immunotherapy is associated with acceptable toxicity and high rates of LC, even with target undercoverage to meet OAR constraints. This suggests a potential for this approach in clinical practice and study in future trials.

Clinical trials have demonstrated the efficacy of bladder-preserving chemoradiation therapy (BPT) in muscle-invasive bladder cancer but have differed in the radiation therapy dose/fractionations, radiation therapy targets, and concurrent chemotherapy regimens used. No data exist on the technical and practical approaches actually used in clinical practice throughout the United States when delivering BPT. We performed a survey to explore radiation oncologists' practice patterns.We conducted an electronic survey of US radiation oncologists regarding the management of patients with cT2-3N0M0 transitional cell muscle-invasive bladder cancer. The instrument included questions regarding the types of patients treated with BPT, as well as several aspects of treatment delivery. Descriptive statistics were reported for all responses. Pearson χIn total, 277 physicians completed our survey. Most respondents (58%) stated that they only treated 1 to 3 patients in the prior year. Seventy-four percent of respondents primarily treated patients deemed unfit for cystectomy, while only 28% saw patients prior to cystectomy for consultation to discuss BPT. The majority of radiation oncologists used conventional fractionation (91%) instead of hypofractionation (7.6%), but more variability existed for radiation therapy targets. Sixty percent used a small pelvis field, 29% used a whole-pelvis field, and 12% treated the bladder only. There was increased use of hypofractionation (29%) and bladder-only radiation therapy (34%) in patients who were not candidates for cystectomy or chemotherapy (P.001). Cisplatin-based concurrent chemotherapy was most commonly preferred (89%). In non-cisplatin candidates, most respondents preferred 5-fluorouracil plus mitomycin C (32%) or carboplatin (32%). Intensity modulated radiation therapy use and midtreatment cystoscopic re-evaluation were variable, while hyperfractionation use was low.Our study describes radiation oncologists' practice patterns for patients undergoing BPT. Although there are areas of consistency, variability exists in many technical and practical aspects of treatment delivery. Further research and education are needed to determine the optimal radiation therapy target, dose/fractionation, and concurrent chemotherapy regimen.

Most historic trials demonstrating the outcomes with bladder-preserving radiotherapy (RT) used 64–66 Gy. However, newer data suggest improved outcomes with dose escalation up to 70 Gy. Our objective was to explore the impact of dose escalation on overall survival (OS) and to identify the optimal radiotherapy (RT) dose in patients with muscle-invasive bladder cancer (MIBC) treated with curative bladder-preserving RT. We conducted a retrospective cohort study of patients with cT2–4 N0–3 M0 transitional cell MIBC who were treated with curative RT (60–70 Gy in 1.8–2.0 Gy/fraction) using the National Cancer Database. Univariable (UVA) and multivariable (MVA) frailty survival analyses were employed to identify the association of dose escalation to 67–70 Gy, as well as different RT dose subgroups within 60–66 Gy, and OS. In total, 2531 patients met eligibility criteria. The 2-year OS was 53 and 56%, respectively, for patients receiving 60–66 and 67–70 Gy (p = .25). On MVA, there was no significant difference in survival for patients receiving 67–70 vs. 60–66 Gy (hazard ratio [HR], 0.91; 95% confidence interval [CI], 0.76–1.10; p = .33). Compared to doses of 64–66 Gy, OS was worse with 60–61 Gy (HR, 1.33; 95% CI, 1.17–1.52; p

Aims Historic trials suggested significant toxicity with adjuvant radiotherapy (ART) after radical cystectomy for muscle-invasive bladder cancer (MIBC). However, recent trials have found improved locoregional control and the 2016 National Comprehensive Cancer Network (NCCN) guidelines recommend ART consideration for select patients at high risk of local recurrence. ART practice patterns among US radiation oncologists are unknown and we carried out a survey to explore current trends. Materials and methods We conducted a survey of US radiation oncologists regarding the management of patients with cT2-3N0M0 transitional cell MIBC. Responses were reported using descriptive statistics. Chi-square and univariate logistic regression of clinical and demographic covariates were conducted, followed by multivariable logistic regression analysis to identify factors predicting for ART use. Results In total, 277 radiation oncologists completed our survey. Nearly half (46%) have used ART for MIBC at least once in the past. In ART users, indications for ART include gross residual disease (93%), positive margins (92%), pathological nodal involvement (64%), pT3 or T4 disease (46%), lymphovascular invasion (16%) and high-grade disease (13%). On univariate logistic regression, ART use was associated with the number of years in practice ( P =0.04), pre-cystectomy radiation oncology consultation ( P =0.004), primarily treating MIBC patients fit for cystectomy ( P =0.01) and intensity-modulated radiotherapy use ( P =0.01). On multivariable logistic regression analysis, routine pre-cystectomy radiation oncology consultation (odds ratio 1.91, 95% confidence interval 1.04–3.51; P =0.04) and intensity-modulated radiotherapy use (odds ratio 2.77, 95% confidence interval 1.48–5.22; P =0.002) remained associated with ART use. Conclusions ART use is controversial in bladder cancer, yet unexpectedly has commonly been used among US radiation oncologists treating patients with MIBC after radical cystectomy. NRG-GU001 was a randomised trial in the US randomizing patients with high-risk pathological findings for observation or ART after cystectomy. However, due to poor accrual it recently closed and thus it will be up to other international trials to clarify the role of ART and identify patients benefiting form this adjuvant therapy.

BACKGROUND The current study was conducted to compare the overall survival (OS) of concurrent chemoradiotherapy (CCRT) versus radiotherapy (RT) alone in elderly patients (those aged ≥80 years) with muscle-invasive bladder cancer (MIBC). METHODS Patients aged ≥80 years with cT2-4, N0-3, M0 transitional cell MIBC who were treated with curative RT (60-70 Gray) or CCRT were identified in the National Cancer Data Base. Univariable and multivariable frailty survival analyses, as well as 1-to-1 propensity score matching, were used to isolate the association between CCRT and OS. RESULTS A total of 1369 patients who were treated with RT from 2004 through 2013 met eligibility criteria: 739 patients (54%) received RT alone and 630 patients (46%) received CCRT. The median age of the patients was 84 years (range, 80-90 years). The median follow-up was 21 months. The 2-year OS rate was 48%. When comparing CCRT with RT alone, the 2-year OS rate was 56% versus 42% (P

Early stage glottic cancer has traditionally been treated with 3D conformal radiotherapy (3DCRT). However, intensity-modulated radiotherapy (IMRT) has been recently adopted as an alternative to decrease toxicity. Here, we compared the usage and outcomes of IMRT and 3DCRT for patients with early stage squamous cell carcinoma (SCC) of the glottic larynx. Using the National Cancer Database, we identified patients with Stage I&ndash, II SCC of the glottis who received 55&ndash, 75 Gy using IMRT (n = 1623) or 3DCRT (n = 2696). Median follow up was 42 months with a 5-year overall survival (OS) of 72%. Using a nominal logistic regression, race, ethnicity, year of diagnosis and fraction size were associated with the receipt of IMRT (p &lt, 0.05). Using Kaplan&ndash, Meier methods and Cox proportional hazards models as well as a propensity matched cohort, there was no difference in OS for patients who received IMRT versus 3DCRT (hazard ratio (HR), 1.08, 95% confidence interval (95% CI), 0.93&ndash, 1.26, p = 0.302). However, there was a survival benefit for patients receiving slight hypofractionation as compared to conventional fractionation (HR, 0.78, 95% CI, 0.69&ndash, 0.92, p = 0.003). IMRT was associated with similar survival as 3DCRT, supporting the implementation of this potentially less toxic modality without compromising survival.

Purpose: To evaluate a method for reducing metal artifacts, arising from dental fillings, on cone-beam computed tomography images. Materials and Methods: A projection interpolation algorithm is applied to cone-beam computed tomography images containing metal artifacts from dental fillings. This technique involves identifying metal regions in individual cone-beam computed tomography projections and interpolating the surrounding values to remove the metal from the projection data. Axial cone-beam computed tomography images are then reconstructed, resulting in a reduction in the streak artifacts produced by the metal. Both phantom and patient imaging data are used to evaluate this technique. Results: The interpolation substitution technique successfully reduced metal artifacts in all cases. Corrected images had fewer or no streak artifacts compared to their noncorrected counterparts. Quantitatively, regions of interest containing the artifacts showed reduced variance in the corrected images versus the uncorrected images. Average pixel values in regions of interest around the metal object were also closer in value to nonmetal regions after artifact reduction. Artifact correction tended to perform better on patient images with less complex metal objects versus those with multiple large dental fillings. Conclusion: The interpolation substitution is potentially an efficient and effective technique for reducing metal artifacts caused by dental fillings on cone-beam computed tomography image. This technique may be effective in reducing such artifacts in patients with head and neck cancer receiving daily image-guided radiotherapy.

Purpose We transitioned from a low-dose-rate (LDR) to a high-dose-rate (HDR) prostate brachytherapy program. The objective of this study was to describe our experience developing a prostate HDR program, compare the LDR and HDR dosimetry, and identify the impact of several targeted interventions in the HDR workflow to improve efficiency. Methods and Materials We performed a retrospective cohort study of patients treated with LDR or HDR prostate brachytherapy. We used iodine-125 seeds (145 Gy as monotherapy, and 110 Gy as a boost) and preoperative planning for LDR. For HDR, we used iridium-192 (13.5 Gy × 2 as monotherapy and 15 Gy × 1 as a boost) and computed tomography–based planning. Over the first 18 months, we implemented several targeted interventions into our HDR workflow to improve efficiency. To evaluate the progress of the HDR program, we used linear mixed-effects models to compare LDR and HDR dosimetry and identify changes in the implant procedure and treatment planning durations over time. Results The study cohort consisted of 122 patients (51 who received LDR and 71 HDR). The mean D90 was similar between patients who received LDR and HDR (P = .28). HDR mean V100 and V95 were higher (P < .0001), but mean V200 and V150 were lower (P < .0001). HDR rectum V100 and D1cc were lower (P < .0001). The HDR mean for the implant procedure duration was shorter (54 vs 60 minutes; P = .02). The HDR mean for the treatment planning duration dramatically improved with the implementation of targeted workflow interventions (3.7 hours for the first quartile to 2.0 hours for the final quartile; P < .0001). Conclusions We successfully developed a prostate HDR brachytherapy program at our institution with comparable dosimetry to our historic LDR patients. We identified several targeted interventions that improved the efficiency of treatment planning. Our experience and workflow interventions may help other institutions develop similar HDR programs.

To quantify, through an observer study, the reduction in metal artifacts on cone beam computed tomographic (CBCT) images using a projection-interpolation algorithm, on images containing metal artifacts from dental fillings and implants in patients treated for head and neck (HN) cancer.An interpolation-substitution algorithm was applied to HN CBCT images containing metal artifacts from dental fillings and implants. Image quality with respect to metal artifacts was evaluated subjectively and objectively. First, 6 independent radiation oncologists were asked to rank randomly sorted blinded images (before and after metal artifact reduction) using a 5-point rating scale (1 = severe artifacts; 5 = no artifacts). Second, the standard deviation of different regions of interest (ROI) within each image was calculated and compared with the mean rating scores.The interpolation-substitution technique successfully reduced metal artifacts in 70% of the cases. From a total of 60 images from 15 HN cancer patients undergoing image guided radiation therapy, the mean rating score on the uncorrected images was 2.3 ± 1.1, versus 3.3 ± 1.0 for the corrected images. The mean difference in ranking score between uncorrected and corrected images was 1.0 (95% confidence interval: 0.9-1.2, P.05). The standard deviation of each ROI significantly decreased after artifact reduction (P.01). Moreover, a negative correlation between the mean rating score for each image and the standard deviation of the oral cavity and bilateral cheeks was observed.The interpolation-substitution algorithm is efficient and effective for reducing metal artifacts caused by dental fillings and implants on CBCT images, as demonstrated by the statistically significant increase in observer image quality ranking and by the decrease in ROI standard deviation between uncorrected and corrected images.

369 Background: Historic trials suggested significant toxicity with adjuvant radiotherapy (ART) after radical cystectomy for muscle-invasive bladder cancer (MIBC). However, recent trials have found improved locoregional control and the 2016 NCCN guidelines recommend ART consideration for select patients at high risk of local recurrence. ART practice patterns among U.S. radiation oncologists (ROs) are unknown, and we performed a survey to explore current trends. Methods: We conducted a survey of U.S. ROs regarding the management of patients with cT2-3N0M0 transitional cell MIBC. Responses were reported using descriptive statistics. Chi-square and univariate logistic regression (UVA) of clinical and demographic covariates were conducted, followed by multivariable logistic regression analyses (MVA) to identify factors predicting for ART use. Results: 277 ROs completed our survey. Nearly half (46%) use ART for MIBC. In ART-users, indications for ART include gross residual disease (93%), positive margins (92%), pathologic nodal involvement (64%), pT3 or T4 disease (46%), lymphovascular invasion (16%), and high-grade disease (13%). On UVA, ART use was associated with the number of years in practice (p=.043), pre-cystectomy RO consultation (p=0.004), primarily treating MIBC patients fit for cystectomy (p=0.009), and intensity-modulated radiotherapy (IMRT) use (p=0.009). On MVA, routine pre-cystectomy RO consultation (odds ratio [OR] 1.91, 95% confidence interval [CI]: 1.04-3.51; p=.037) and IMRT use (OR 2.77, 95% CI: 1.48-5.22; p=.002) remained associated with ART use. Conclusions: ART use is controversial in bladder cancer, yet is unexpectedly commonly used among U.S. radiation oncologists treating patients with MIBC after radical cystectomy. NRG GU001 is a randomized trial currently accruing patients with high-risk pathologic findings for observation or ART after cystectomy, and will hopefully clarify the role of ART and help identify patients benefiting from this adjuvant therapy. Whenever possible, patients should be enrolled in this study.

295 Background: Excellent outcomes with bladder-preserving trimodality therapy have been demonstrated at centers with expertise and high-volume. Some argue that these results may not be replicated at other centers with lower case volumes. We analyzed the National Cancer Database to determine if treatment at a high-volume facility is associated with improved overall survival (OS) for patients undergoing radiotherapy (RT) or chemoradiotherapy (CRT) for non-metastatic muscle-invasive bladder cancer (MIBC). Methods: Patients with cT2-4 N0-3 M0 transitional cell MIBC treated with RT or CRT were selected. The case volume variable was derived by calculating a count of patient records by each facility using the entire database of 439,188 patients. Multivariate analysis (MVA) was performed using the Cox proportional hazards model, which was used to assess the association of case volume with OS while controlling for clinicodemographic and treatment factors associated with OS on univariate analysis, including clustering of patients within their treatment facility type. Results: 872 patients treated with radiotherapy from 2008-2012 at 452 unique facilities were identified. 502 (58%) patients received RT, and 370 (42%) patients received CRT. The median case volume at each unique facility was 376 cases with an interquartile range of 235 – 579 cases. In the entire radiotherapy cohort, MVA controlling for patient case load, age, sex, education, T Stage, N Stage, cumulative radiotherapy dose, Charlson-Deyo comorbidity score, and geographic location, demonstrated that treatment at a facility with a higher case volume was associated with improved OS. For every 250 patient increase in facility case volume, the hazard of death at any given time for patients receiving radiotherapy decreased by 7% (HR = 0.93, 95% CI: 0.87 – 0.98, p = .01). Conclusions: To the authors’ knowledge, this is the first analysis demonstrating an association between treatment facility case volume and OS in the treatment of MIBC patients with RT or CRT. Consideration should be given to referring patients to high volume facilities for treatment of MIBC.

The creation of a new material often starts from the design of its constituent building blocks at a smaller scale. From macromolecules to colloidal architectures, to granular systems, the interactions between basic units of matter can dictate the macroscopic behaviour of the resulting engineered material and even regulate its genesis. Information can be imparted to the building units by altering their physical and chemical properties. In particular, the shape of building blocks has a fundamental role at the colloidal scale, as it can govern the self-organization of particles into hierarchical structures and ultimately into the desired material. Herein we report a simple and general approach to generate an entire zoo of new anisotropic colloids. Our method is based on a controlled deformation of multiphase colloidal particles that can be selectively liquified, polymerized, dissolved and functionalized in bulk. We further demonstrate control over the particle functionalization and coating by realizing patchy and Janus colloids.