Total body irradiation delivered using a dedicated Co-60 TBI unit: Evaluation of dosimetric uniformity and dose verification.

This work presents the dosimetric characteristics of Total Body Irradiation (TBI) delivered using a dedicated Co-60 TBI unit. We demonstrate the ability to deliver a uniform dose to the entire patient without the need for a beam spoiler or patient-specific compensation. Full dose distributions are calculated using an in-house Monte Carlo treatment planning system, and cumulative dose distributions are created by deforming the dose distributions within two different patient orientations. Sample dose distributions and profiles are provided to illustrate the plan characteristics, and dose and DVH statistics are provided for a heterogeneous cohort of patients. The patient cohort includes adult and pediatric patients with a range of 132-198 cm in length and 16.5-37.5 cm in anterior-posterior thickness. With the exception of the lungs, a uniform dose of 12 Gy is delivered to the patient with nearly the entire volume receiving a dose within 10% of the prescription dose. Mean lung doses (MLDs) are maintained below the estimated threshold for radiation pneumonitis, with MLDs ranging from 7.3 to 9.3 Gy (estimated equivalent dose in 2 Gy fractions (EQD2 ) of 6.2-8.5 Gy). Dose uniformity is demonstrated across five anatomical locations within the patient for which mean doses are all within 3.1% of the prescription dose. In-vivo dosimetry demonstrates excellent agreement between measured and calculated doses, with 78% of measurements within ±5% of the calculated dose and 99% within ±10%. These results demonstrate a state-of-the-art TBI planning and delivery system using a dedicated TBI unit and hybrid in-house and commercial planning techniques which provide comprehensive dosimetric data for TBI treatment plans that are accurately verified using in-vivo dosimetry.

MVCT versus kV-CBCT for targets subject to respiratory motion: A phantom study.

The use of kilovoltage cone-beam computed tomography (kV-CBCT) or megavoltage computed tomography (MVCT) for image guidance prior to lung stereotactic body radiation therapy (SBRT) is common clinical practice. We demonstrate that under equivalent respiratory conditions, image guidance using both kV-CBCT and MVCT may result in the inadequate estimation of the range of target motion under free-breathing (FB) conditions when standard low-density window and levels are used. Two spherical targets within a respiratory motion phantom were imaged using both long-exhale (LE) and sinusoidal respiratory traces. MVCT and kV-CBCT images were acquired and evaluated for peak-to-peak amplitudes of 10 or 20 mm in the cranial-caudal direction, and with 2, 4 or 5 s periods. All images were visually inspected for artifacts and conformity to the ITV for each amplitude, period, trace-type, and target size. All LE respiratory traces required a lower threshold HU window for MVCT and kV-CBCT compared to sinusoidal traces to obtain 100% volume conformity compared with the theoretical ITV (ITVT ). Excess volume was less than 2% for all kV-CBCT contours regardless of trace-type, breathing period, or amplitude, while the maximum excess volume for MVCT was 48%. Adjusting window and level to maximize conformity with the ITVT is necessary to reduce registration uncertainty to less than 5 mm. To fully capture target motion with either MVCT or kV-CBCT, substantial changes in HU levels up to -600 HU are required which may not be feasible clinically depending on the target's location and surrounding tissue contrast. This registration method, utilizing a substantially decreased window and level compared to standard low-density settings, was retrospectively compared to the automated registration algorithm for five lung SBRT patients exposed to pre-treatment kV-CBCT image guidance. Differences in registrations in the super-inferior (SI) direction greater than the commonly used ITV to PTV margin of 5 mm were encountered for several cases. In conclusion, pre-treatment image guidance for lung SBRT targets using MVCT or kV-CBCT is unlikely to capture the full extent of target motion as defined by the ITVT and additional caution is warranted to avoid registration errors for small targets and patients with LE respiratory traces.

Patterns and predictors of failure following tri-modality therapy for locally advanced esophageal cancer.

BACKGROUND: Although tri-modality therapy is an acceptable standard of care in patients with locally advanced esophageal cancer, data regarding patterns of failure is lacking. We report bi-institutional patterns of failure experience treating patients using tri-modality therapy. MATERIALS AND METHODS: We retrospectively reviewed patients who underwent chemoradiation followed by esophagectomy between 2006 and 2011 at two NCI-designated cancer centers. First failure sites were categorized as local, regional nodal, or distant. Statistical analysis was performed using Fisher's exact test, non-parametric Wilcoxon rank-sum test, and multiple logistic regression. Kaplan-Meier curves were generated for relapse-free survival (RFS) and overall survival. RESULTS: A total of 132 patients met the inclusion criteria with a median age of 62 (range 36-80) and median follow-up of 28 months (range 4-128). There were a total of six (4.5%) local, 13 (10%) regional nodal, and 32 (23.5%) distant failures. Local failure was correlated with fewer lymph nodes (LN) assessed (p = 0.01) and close/positive margins (p < 0.01). Regional nodal failure was correlated with fewer LN assessed (p < 0.01) and larger pretreatment tumor size (p = 0.04). Patients with ≤13 LN evaluated had an inferior locoregional RFS versus patients with >13 LN evaluated (p = 0.003). Distant recurrence was correlated with higher pathologic nodal stage (p < 0.001), ulceration (p = 0.017), perineural invasion (p = 0.029), residual disease (p = 0.004), and higher post-treatment PET SUV max (p = 0.049). Patients with a pathologic complete response (OR 0.19, 95% CI 0.05-0.68) were less likely to experience distant recurrence. CONCLUSION: Tumor and treatment factors may predict for failure in patients undergoing tri-modality therapy for locally advanced esophageal cancer. Further data is needed to identify patterns of failure in these patients.

Predictors of Early Hospice or Death in Patients With Inoperable Lung Cancer Treated With Curative Intent.

INTRODUCTION: Treatment for inoperable stage II to III non-small cell lung cancer (NSCLC) involves chemo-radiotherapy (CRT). However, some patients transition to hospice or die early during their treatment course. We present a model to prognosticate early poor outcomes in NSCLC patients treated with curative-intent CRT. METHODS AND MATERIALS: Across a statewide consortium, data was prospectively collected on stage II to III NSCLC patients who received CRT between 2012 and 2019. Early poor outcomes included hospice enrollment or death within 3 months of completing CRT. Logistic regression models were used to assess predictors in prognostic models. LASSO regression with multiple imputation were used to build a final multivariate model, accounting for missing covariates. RESULTS: Of the 2267 included patients, 128 experienced early poor outcomes. Mean age was 71 years and 59% received concurrent chemotherapy. The best predictive model, created parsimoniously from statistically significant univariate predictors, included age, ECOG, planning target volume (PTV), mean heart dose, pretreatment lack of energy, and cough. The estimated area under the ROC curve for this multivariable model was 0.71, with a negative predictive value of 95%, specificity of 97%, positive predictive value of 23%, and sensitivity of 16% at a predicted risk threshold of 20%. CONCLUSIONS: This multivariate model identified a combination of clinical variables and patient reported factors that may identify individuals with inoperable NSCLC undergoing curative intent chemo-radiotherapy who are at higher risk for early poor outcomes.

Are We Missing Acute Toxicities Associated With Hypofractionated Breast Irradiation? A Report From a Large Multicenter Cohort Study.

PURPOSE: The efficacy and long-term safety of hypofractionated whole breast irradiation (HF-WBI) have been established through multiple randomized trials, yet data about acute toxicities remain more limited. Since 2013, our group has prospectively collected acute toxicity data from weekly treatment evaluations and additional assessment after completion. In 2016, we intentionally shifted the posttreatment assessment follow-up visit from 1 month to 2 weeks to evaluate for missed acute toxicity occurring in that immediate posttreatment window. Here, we report whether 2-week follow-up has resulted in increased detection of acute toxicities compared with 4-week follow-up. METHODS AND MATERIALS: We prospectively compared acute toxicity for patients treated with HF-WBI between January 1, 2013, and August 31, 2015 (4 week follow-up cohort) to patients treated between January 1, 2016, and August 31, 2018 (2 week follow-up cohort). Analyses included a multivariable model that adjusted for other factors known to correlate with toxicity. We prospectively defined acute toxicity as maximum breast pain (moderate or severe rating) and/or occurrence of moist desquamation reported 7 days before the completion of radiation therapy (RT) until 42 days after completion. RESULTS: A total of 2689 patients who received postlumpectomy radiation and boost were analyzed; 1862 patients in the 2-week follow-up cohort and 827 in the 4-week follow-up cohort. All acute toxicity measures assessed were statistically similar between follow-up cohorts when compared in an unadjusted fashion. Overall acute composite toxicity was 26.4% and 27.7% for patients in the 4-week follow-up and 2-week follow-up cohorts, respectively. Overall acute composite toxicity remained similar between follow-up cohorts in a multivariable, adjusted model and was significantly related to patient's age, body mass index, smoking status, and treatment technique (intensity-modulated RT vs 3-dimensional conformal radiation therapy) but not follow-up cohort. CONCLUSIONS: An earlier posttreatment follow-up for HF-WBI patients did not reveal a significant increased incidence of acute toxicities at 2 weeks compared with 4 weeks. This study provides physicians and patients with additional data on the safety and tolerability of HF-WBI for early stage breast cancer.

Proton versus photon radiation therapy: A clinical review.

While proton radiation therapy offers substantially better dose distribution characteristics than photon radiation therapy in certain clinical applications, data demonstrating a quantifiable clinical advantage is still needed for many treatment sites. Unfortunately, the number of patients treated with proton radiation therapy is still comparatively small, in some part due to the lack of evidence of clear benefits over lower-cost photon-based treatments. This review is designed to present the comparative clinical outcomes between proton and photon therapies, and to provide an overview of the current state of knowledge regarding the effectiveness of proton radiation therapy.

A Direct Patient-Provider Relationship With the Medical Physicist Reduces Anxiety in Patients Receiving Radiation Therapy.

PURPOSE: The complex technological processes involved in radiation therapy can be intimidating to patients, causing increased treatment-related anxiety and reduced satisfaction. An intervention was implemented to provide direct consultations between patients and medical physicists to reduce patient anxiety and improve patient satisfaction. A randomized clinical trial was conducted to test the intervention's effect on anxiety, distress, treatment adherence, technical understanding, and satisfaction in patients receiving radiation therapy. METHODS AND MATERIALS: Eligible patients were recruited into "intervention" and "standard of care" arms within a phase 2 screening randomized trial. Intervention-arm patients met with a medical physicist who provided technical information and addressed patient questions or concerns at the time of treatment simulation and before the first treatment. In addition to baseline information collected before randomization, participants were surveyed (1) before simulation, (2) before the first treatment, and (3) before the completion of treatment to evaluate the study endpoints. Primary endpoints included patient anxiety and distress. Secondary endpoints included patient treatment adherence, overall satisfaction, and technical understanding of treatment. Patients in the intervention arm were surveyed before and after each physicist meeting. RESULTS: Participant anxiety was significantly reduced in the intervention arm (difference, -0.29; 95% confidence interval, -0.57 to -0.02; P = .038). No differences in distress or treatment adherence were observed between groups. Although measures of technical understanding and satisfaction were evaluated as exploratory objectives, participants in the intervention group were more likely to feel that technical aspects of treatment were adequately explained (difference, 0.78; 95% confidence interval, 0.03-1.54), and all measures of technical understanding and satisfaction were considerably higher in the intervention group at the time of the first visit. CONCLUSIONS: The establishment of a direct patient-provider relationship with the medical physicist reduced anxiety in patients receiving radiation therapy. In addition, increases in patient understanding of the technical aspects of care and in satisfaction were observed at the initiation of treatment.

Prospective Evaluation of Limited-Stage Small Cell Lung Cancer Radiotherapy Fractionation Regimen Usage and Acute Toxicity in a Large Statewide Quality Collaborative.

PURPOSE: National guidelines on limited-stage small cell lung cancer (LS-SCLC) treatment give preference to a hyperfractionated regimen of 45 Gy in 30 fractions delivered twice daily; however, use of this regimen is uncommon compared with once-daily regimens. The purpose of this study was to characterize the LS-SCLC fractionation regimens used throughout a statewide collaborative, analyze patient and treatment factors associated with these regimens, and describe real-world acute toxicity profiles of once- and twice-daily radiation therapy (RT) regimens. METHODS AND MATERIALS: Demographic, clinical, and treatment data along with physician-assessed toxicity and patient-reported outcomes were prospectively collected by 29 institutions within the Michigan Radiation Oncology Quality Consortium between 2012 and 2021 for patients with LS-SCLC. We modeled the influence of RT fractionation and other patient-level variables clustered by treatment site on the odds of a treatment break specifically due to toxicity with multilevel logistic regression. National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0, incident grade 2 or worse toxicity was longitudinally compared between regimens. RESULTS: There were 78 patients (15.6% overall) treated with twice-daily RT and 421 patients treated with once-daily RT. Patients receiving twice-daily RT were more likely to be married or living with someone (65% vs 51%; P = .019) and to have no major comorbidities (24% vs 10%; P = .017). Once-daily RT fractionation toxicity peaked during RT, and twice-daily toxicity peaked within 1 month after RT. After stratifying by treatment site and adjusting for patient-level variables, once-daily treated patients had 4.11 (95% confidence interval, 1.31-12.87) higher odds of treatment break specifically due to toxicity than twice-daily treated patients. CONCLUSIONS: Hyperfractionation for LS-SCLC remains infrequently prescribed despite the lack of evidence demonstrating superior efficacy or lower toxicity of once-daily RT. With peak acute toxicity after RT and lower likelihood of a treatment break with twice-daily fractionation in real-word practice, providers may start using hyperfractionated RT more frequently.

Quality and Safety Considerations in Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy: An ASTRO Safety White Paper Update.

PURPOSE: This updated report on stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) is part of a series of consensus-based white papers previously published addressing patient safety. Since the first white papers were published, SRS and SBRT technology and procedures have progressed significantly such that these procedures are now more commonly used. The complexity and submillimeter accuracy, and delivery of a higher dose per fraction requires an emphasis on best practices for technical, dosimetric, and quality assurance. Therefore, quality and patient safety considerations for these techniques remain an important area of focus. METHOD: The American Society for Radiation Oncology convened a task force to assess the original SRS/SBRT white paper and update content where appropriate. Recommendations were created using a consensus-building methodology and task force members indicated their level of agreement based on a 5-point Likert scale, from "strongly agree" to "strongly disagree." A prespecified threshold of ≥75% of raters who select "strongly agree" or "agree" indicated consensus. SUMMARY: This white paper builds on the previous version and uses of other guidance documents to broadly address SRS and SBRT delivery, primarily focusing on processes related to quality and safety. SRS and SBRT require a team-based approach, staffed by appropriately trained and credentialed specialists as well as significant personnel resources, specialized technology, and implementation time. A thorough feasibility analysis of resources is required to achieve the clinical and technical goals and thoroughly discussed with all personnel before undertaking new disease sites. A comprehensive quality assurance program must be developed, using established treatment guidelines, to ensure SRS and SBRT are performed in a safe and effective manner. Patient safety in SRS/SBRT is everyone's responsibility and professional organizations, regulators, vendors, and end-users must demonstrate a clear commitment to working together to ensure the highest levels of safety.

The Impact of Chemotherapy on Toxic Effects and Cosmetic Outcome in Patients Receiving Whole Breast Irradiation: An Analysis Within a Statewide Quality Consortium.

PURPOSE: We investigated whether the use of chemotherapy before whole breast irradiation (WBI) using either conventional fractionation (CWBI) or hypofractionation (HWBI) is associated with increased toxic effects or worse cosmetic outcome compared with WBI alone. METHODS AND MATERIALS: We identified 6754 patients who received WBI alone (without a third field covering the superior axillary and supraclavicular nodal regions) with data prospectively collected in a statewide consortium. We reported rates of 4 toxic effects: physician-reported acute moist desquamation, patient-reported acute moderate/severe breast pain, a composite acute toxic effect measure (including moist desquamation and either patient- or physician-reported moderate/significant breast pain), and physician-reported impaired cosmetic outcome at 1 year after WBI. Successive multivariable models were constructed to estimate the effect of chemotherapy on these outcomes. RESULTS: Rates of moist desquamation, patient-reported pain, composite acute toxic effects, and impaired cosmetic outcome were 23%, 34%, 42%, and 10% for 2859 patients receiving CWBI and 13%, 28%, 31%, and 11% for 3895 patients receiving HWBI. Receipt of chemotherapy before CWBI was not associated with higher rates of patient-reported pain, composite acute toxic effects, or impaired cosmetic outcome compared with CWBI without chemotherapy but was associated with more moist desquamation (odds ratio, 1.32 [1.07-1.63]; P = .01). Receipt of chemotherapy before HWBI was not associated with higher rates of any of the 4 toxic effects compared with HWBI alone. CONCLUSIONS: In this cohort, use of chemotherapy before WBI was generally well tolerated. CWBI with chemotherapy but not HWBI with chemotherapy was associated with higher rates of moist desquamation. Rates of acute breast pain and impaired cosmetic outcome at 1 year were comparable in patients receiving chemotherapy before either CWBI or HWBI. These data support the use of HWBI after chemotherapy.

Uptake of Adjuvant Durvalumab After Definitive Concurrent Chemoradiotherapy for Stage III Nonsmall-cell Lung Cancer.

OBJECTIVES: The addition of adjuvant durvalumab improves overall survival in locally advanced nonsmall-cell lung cancer (NSCLC) patients treated with definitive chemoradiation, but the real-world uptake of adjuvant durvalumab is unknown. MATERIALS AND METHODS: We identified patients with stage III NSCLC treated with definitive concurrent chemoradiation from January 2018 to October 2020 from a statewide radiation oncology quality consortium, representing a mix of community (n=22 centers) and academic (n=5) across the state of Michigan. Use of adjuvant durvalumab was ascertained at the time of routine 3-month or 6-month follow-up after completion of chemoradiation. RESULTS: Of 421 patients with stage III NSCLC who completed chemoradiation, 322 (76.5%) initiated adjuvant durvalumab. The percentage of patients initiating adjuvant durvalumab increased over time from 66% early in the study period to 92% at the end of the study period. There was substantial heterogeneity by treatment center, ranging from 53% to 90%. In multivariable logistic regression, independent predictors of durvalumab initiation included more recent month (odds ratio [OR]: 1.05 per month, 95% confidence interval [CI]: 1.02-1.08, P=0.003), lower Eastern Cooperative Oncology Group score (OR: 4.02 for ECOG 0 vs. 2+, 95% CI: 1.67-9.64, P=0.002), and a trend toward significance for female sex (OR: 1.66, 95% CI: 0.98-2.82, P=0.06). CONCLUSION: Adjuvant durvalumab for stage III NSCLC treated with definitive chemoradiation was rapidly and successfully incorporated into clinical care across a range of community and academic settings in the state of Michigan, with over 90% of potentially eligible patients starting durvalumab in more recent months.

Comparative Effectiveness Analysis of 3D-Conformal Radiation Therapy Versus Intensity Modulated Radiation Therapy (IMRT) in a Prospective Multicenter Cohort of Patients With Breast Cancer.

PURPOSE: Simple intensity modulation of radiation therapy reduces acute toxicity compared with 2-dimensional techniques in adjuvant breast cancer treatment, but it remains unknown whether more complex or inverse-planned intensity modulated radiation therapy (IMRT) offers an advantage over forward-planned, 3-dimensional conformal radiation therapy (3DCRT). METHODS AND MATERIALS: Using prospective data regarding patients receiving adjuvant whole breast radiation therapy without nodal irradiation at 23 institutions from 2011 to 2018, we compared the incidence of acute toxicity (moderate-severe pain or moist desquamation) in patients receiving 3DCRT versus IMRT (either inverse planned or, if forward-planned, using ≥5 segments per gantry angle). We evaluated associations between technique and toxicity using multivariable models with inverse-probability-of-treatment weighting, adjusting for treatment facility as a random effect. RESULTS: Of 1185 patients treated with 3DCRT and conventional fractionation, 650 (54.9%) experienced acute toxicity; of 774 treated with highly segmented forward-planned IMRT, 458 (59.2%) did; and of 580 treated with inverse-planned IMRT, 245 (42.2%) did. Of 1296 patients treated with hypofractionation and 3DCRT, 432 (33.3%) experienced acute toxicity; of 709 treated with highly segmented forward-planned IMRT, 227 (32.0%) did; and of 623 treated with inverse-planned IMRT, 164 (26.3%) did. On multivariable analysis with inverse-probability-of-treatment weighting, the odds ratio for acute toxicity after inverse-planned IMRT versus 3DCRT was 0.64 (95% confidence interval, 0.45-0.91) with conventional fractionation and 0.41 (95% confidence interval, 0.26-0.65) with hypofractionation. CONCLUSIONS: This large, prospective, multicenter comparative effectiveness study found a significant benefit from inverse-planned IMRT compared with 3DCRT in reducing acute toxicity of breast radiation therapy. Future research should identify the dosimetric differences that mediate this association and evaluate cost-effectiveness.

Association Between Physician- and Patient-Reported Symptoms in Patients Treated With Definitive Radiation Therapy for Locally Advanced Lung Cancer in a Statewide Consortium.

PURPOSE: Little data have been reported about the patient experience during curative radiation therapy (RT) for lung cancer in routine clinical practice or how this relates to treatment toxicity as reported by clinicians. The purpose of this study was to compare clinician-reported adverse events (AEs) with patient-reported outcomes (PROs), including both specific symptoms/side effects, as well as overall quality of life (QoL) during and after definitive RT for locally advanced lung cancer (LALC) in a large statewide cohort. METHODS AND MATERIALS: PROs were prospectively collected from patients treated with definitive RT for LALC at 24 institutions within the Michigan Radiation Oncology Quality Consortium between 2012 and 2018 using the Functional Assessment of Cancer Therapy trial outcome index. Physicians prospectively recorded AEs using the Common Terminology Criteria for Adverse Events, version 4.0. Patient-reported QoL changes from baseline were assessed during and after RT using the Functional Assessment of Cancer Therapy trial outcome index. Spearman correlation coefficients were calculated for AEs and similar PROs, and a multivariable analysis was used to assess associations with QoL. RESULTS: A total 1361 patients were included in the study, and 53% of respondents reported clinically meaningful declines in QoL at the end of RT. The correlation between clinician-reported esophagitis and patient-reported trouble swallowing was moderate (R = .67), but correlations between clinician-reported pneumonitis and patient-reported shortness of breath (R = .13) and cough (R = .09) were weak. Clinician-reported AEs were significantly associated with clinically meaningful declines in patient-reported QoL (R = - .46 for summary AE score). QoL was more strongly associated with fatigue (R = - .41) than lung-specific AEs. CONCLUSIONS: AEs are associated with clinically meaningful declines in QoL during and after RT for LALC, but associations between AEs and QoL are only modest. This highlights the importance of PRO data, and future research should assess whether earlier detection of PRO changes could allow for interventions that reduce the frequency of treatment-related clinically meaningful declines in QoL.

ACR-ACNM-ASTRO-SNMMI Practice Parameter for Lutetium-177 (Lu-177) DOTATATE Therapy.

OBJECTIVES: This practice parameter (PP) for Lutetium-177 (Lu-177) DOTATATE peptide receptor radionuclide therapy (PRRT) aims to guide authorized users in selection of appropriate adult candidates with gastroeneropancreatic neuroendocrine tumors (GEP-NETs) from foregut, midgut, and hindgut. The essential selection criteria include somatostatin receptor-positive GEP-NETs, which are usually inoperable and progressed despite standard therapy. Lu-177 DOTATATE is a radiopharmaceutical with high avidity for somatostatin receptors that are overexpressed by these tumors. This document ensures safe handling of Lu-177 DOTATATE by the authorized users and safe management of affected patients. METHODS: The document was developed according to the systematic process developed by the American College of Radiology (ACR) and described on the ACR Web site (https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards). The PP development was led by 2 ACR Committees on Practice Parameters (Nuclear Medicine and Molecular Imaging and Radiation Oncology) collaboratively with the American College of Nuclear Medicine, American Society of Radiation Oncology, and Society of Nuclear Medicine and Molecular Imaging. RESULTS: The Lu-177 DOTATATE PP reviewed pharmacology, indications, adverse effects, personnel qualifications, and required clinical evaluation before starting the treatment, as well as the recommended posttherapy monitoring, quality assurance, documentation, and appropriate radiation safety instructions provided in written form and explained to the patients. CONCLUSIONS: Lu-177 DOTATATE is available for therapy of inoperable and/or advanced GEP-NETs when conventional therapy had failed. It can reduce tumor size, improve symptoms, and increase the progression free survival. The PP document provides clinical guidance for authorized users to assure an appropriate, consistent, and safe practice of Lu-177 DOTATATE.