Comparison of failure modes and effects analyses and time for brachytherapy ring and tandem applicator digitization between manual and solid applicator source placement methods.

PURPOSE: Ring and tandem (R&T) applicator digitization is currently performed at our institution by manually defining the extent of the applicators. Digitization can also be achieved using solid applicators: predefined, 3D models with geometric constraints. This study compares R&T digitization using manual and solid applicator methods through Failure Modes and Effects Analyses (FMEAs) and comparative time studies. We aim to assess the suitability of solid applicator method implementation for R&T cases METHODS: Six qualified medical physicists (QMPs) and two medical physics residents scored potential modes of failure of manual digitization in an FMEA as recommended by TG-100. Occurrence, severity, and detectability (OSD) values were averaged across respondents and then multiplied to form combined Risk Priority Numbers (RPNs) for analysis. Participants were trained to perform treatment planning using a developed solid applicator protocol and asked to score a second FMEA on the distinct process steps from the manual method. For both methods, participant digitization was timed. FMEA and time data were analyzed across methods and participant samples RESULTS: QMPs rated the RPNs of the current, manual method of digitization statistically lower than residents did. When comparing the unique FMEA steps between the two digitization methods, QMP respondents found no significant difference in RPN means. Residents, however, rated the solid applicator method as higher risk. Further, after the solid applicator method was performed twice by participants, the time to digitize plans was not significantly different from manual digitization CONCLUSIONS: This study indicates the non-inferiority of the solid applicator method to manual digitization in terms of risk, according to QMPs, and time, across all participants. Differences were found in FMEA evaluation and solid applicator technique adoption based on years of brachytherapy experience. Further practice with the solid applicator protocol is recommended because familiarity is expected to lower FMEA occurrence ratings and further reduce digitization times.

Multi-phase failure modes and effects analysis for low dose bilateral whole lung irradiation of COVID-19 positive patients requiring respiratory ventilation.

PURPOSE: To identify high-priority risks in a clinical trial investigating the use of radiation to alleviate COVID-19 pneumonia using a multi-phase failure modes and effects analysis (FMEA). METHODS: A comprehensive FMEA survey of 133 possible causes of failure was developed for the clinical trial workflow (Phase I). The occurrence, severity, and detection risk of each possible cause of failure was scored by three medical physicists. High-risk potential failure modes were identified using the risk priority number (RPN) and severity scores, which were re-scored by 13 participants in radiation oncology (Phase II). Phase II survey scores were evaluated to identify steps requiring possible intervention and examine risk perception patterns. The Phase II participants provided consensus scores as a group. RESULTS: Thirty high-priority failure modes were selected for the Phase II survey. Strong internal consistency was shown in both surveys using Cronbach's alpha (αc ≥ 0.85). The 10 failures with the largest median RPN values concerned SARS-CoV-2 transmission (N = 6), wrong treatment (N = 3), and patient injury (N = 1). The median RPN was larger for COVID-related failures than other failure types, primarily due to the perceived difficulty of failure detection. Group re-scoring retained 8/10 of the highest-priority risk steps that were identified in the Phase II process, and discussion revealed interpretation differences of process steps and risk evaluation. Participants who were directly involved with the trial working group had stronger agreement on severity scores than those who were not. CONCLUSIONS: The high ranking of failures concerning SARS-CoV-2 transmission suggest that these steps may require additional quality management intervention when treating critically ill COVID-19+ patients. The results also suggest that a multi-phase FMEA survey led by a facilitator may be a useful tool for assessing risks in radiation oncology procedures, supporting future efforts to adapt FMEA to clinical procedures.

Blinding of Residency Applications in Medical Physics: Promises and Pitfalls.

Purpose: The feasibility of blinding applications for a medical physics residency program has yet to be demonstrated in the literature. We explore the application of an automated approach with human review and intervention to blind applications during the annual medical physics residency review cycle. Methods and Materials: Applications were blinded using an automated process and used for the first phase of residency review in the program. We retrospectively compared self-reported demographic and gender data with blinded and nonblinded cohorts from 2 sequential years of review from a medical physics residency program. Demographic data were analyzed comparing applicants with candidates selected to move to the next phase of the review process. Interrater agreement was also evaluated from the applicant reviewers. Results: We show the feasibility of blinding applications for a medical physics residency program. We observed no more than a 3% difference between the gender selection within the first phase of application review but greater differences when examining race and ethnicity between the 2 methods. The greatest difference was shown to be between Asian and White candidates, where there are statistical differences in the scores in the rubric categories of essay and overall impression. Conclusions: We suggest that each training program critically evaluate its selection criteria for potential sources of bias within the review process. We recommend further critical investigation of processes to promote equity and inclusion to ensure the methods and outcomes are aligned with the mission of the program. Finally, we recommend that the common application provide an option for blinding applications at the source so this can be an option to facilitate efforts for evaluating unconscious bias in the review process.

An introduction to key performance indicators for medical physicists.

Qualified medical physicists (QMPs) are in a unique position to influence the creation and application of key performance indicators (KPIs) across diverse practices in health care. Developing KPIs requires the involvement of stakeholders in the area of interest. Fundamentally, KPIs should provide actionable information for the stakeholders using or viewing them. During development, it is important to strongly consider the underlying data collection for the KPI, making it automatic whenever possible. Once the KPI has been validated, it is important to setup a review cycle and be prepared to adjust the underlying data or action levels if the KPI is not performing as intended. Examples of specific KPIs for QMPs of common scopes of practice are provided to act as models to aid in implementation. KPIs are a useful tool for QMPs, regardless of the scope of practice or practice environment, to enhance the safety and quality of care being delivered.

A novel methodology for the optimization of transmission and dosimetric leaf gap parameters.

PURPOSE: Optimization of dosimetric leaf gap (DLG) and transmission is commonly performed through a manual trial and error process, which can lead to sub-optimal values. The purpose of this work is to create an alternative automated optimization process that provides the optimal DLG and transmission pair for use in a clinical setting. METHODS: Utilizing the treatment planning system application programming interface, a phase space of clinically viable DLG and transmission pairs was generated. The phase space contained 51,051 dose planes for DLGs between 0.0  and 2.5 mm and transmission values between 0.01% and 2.5%. Thirteen plans were measured for multiple multileaf collimator types and nominal beam energies. The optimization minimized the mean γ-index and maximized the γ-index pass rate. The optimized values were validated using five plans excluded from the optimization. RESULTS: Of the nominal beam energies and multileaf collimator system (MLC)-type combinations tested, 6/7 showed an increase in γ-index pass rate and a decrease in mean γ-index signifying better agreement between measurement and calculation. When comparing the optimized DLG and transmission values to the clinically implemented values identified via an iterative method, 5/7 energy, and MLC type combinations showed no statistically significant changes. In addition, the optimized values were benchmarked against three Task Group 119 plans with published γ-index pass rates, which had been held out of the optimization. For those plans, the optimized DLG and transmission values provided the same or better γ-index pass rates. CONCLUSION: We presented a novel and viable automated alternative to current approaches of selecting the DLG and transmission parameters. This method will reduce the time required to determine the clinically acceptable DLG and transmission parameters and ensure optimality for the plans included in the optimization.

The lifetime of a linac monitor unit ion chamber.

This study is the first to report the clinical lifetime of Varian Kapton sealed ion chambers as a retrospective review. The data have been analyzed using ion chamber gain values, daily quality assurance results, monthly quality assurance results, and delivered treatment field data were analyzed to comprehensively review trends. The data show the average lifetimes of the ion chambers from our institution, so other physicists can prepare for replacement. Additionally, we share our experience in performing quality assurance tests to calibrate and validate the radiation beam after ion chamber replacement.

Analysis of Radiation Dose to the Shoulder by Treatment Technique and Correlation With Patient Reported Outcomes in Patients Receiving Regional Nodal Irradiation.

BACKGROUND/PURPOSE: Shoulder/arm morbidity is a late complication of breast cancer treatment with surgery and regional nodal irradiation (RNI). We set to analyze the impact of radiation technique [intensity modulated radiation therapy (IMRT) or 3D conformal radiation therapy (3DCRT)] on radiation dose to the shoulder with a hypothesis that IMRT use results in smaller volume of shoulder receiving radiation. We explored the relationship of treatment technique on long-term patient-reported outcomes using the quick disabilities of the arm, shoulder, and hand (q-DASH) questionnaire. MATERIALS/METHODS: We identified patients treated with adjuvant RNI (50 Gy/25 fractions) from 2013 to 2018. We retrospectively contoured the shoulder organ-at-risk (OAR) from 2 cm above the ipsilateral supraclavicular (SCL) planning target volume (PTV) to the inferior SCL PTV slice and calculated the absolute volume of shoulder OAR receiving 5-50 Gy (V5-V50). We identified patients that completed a q-DASH questionnaire ≥6 months from the end of RNI. RESULTS: We included 410 RNI patients: 54% stage III, 72% mastectomy, 35% treated with IMRT. IMRT resulted in significant reductions in the shoulder OAR volume receiving 20-50 Gy vs. 3DCRT. In total, 82 patients completed the q-DASH. The mean (SD) q-DASH=25.4 (19.1) and tended to be lower with IMRT vs. 3DCRT: 19.6 (16.4) vs. 27.8 (19.8), p=0.078. CONCLUSION: We found that IMRT reduces radiation dose to the shoulder and is associated with a trend toward reduced q-DASH scores ≥6 months post-RNI in a subset of our cohort. These results support prospective evaluation of IMRT as a technique to reduce shoulder morbidity in breast cancer patients receiving RNI.

Increasing neutrophil-to-lymphocyte ratio following radiation is a poor prognostic factor and directly correlates with splenic radiation dose in pancreatic cancer.

PURPOSE: Neutrophil-to-lymphocyte ratio has been correlated with clinical outcomes in many cancers. We investigated whether the delta-NLR (ΔNLR) following radiation therapy (RT) could predict achieving surgical resection and the overall survival (OS) of patients with borderline resectable (BRPC) and locally advanced pancreatic cancer (LAPC), and whether the splenic radiation dose impacted ΔNLR. METHODS/MATERIALS: 101 patients with biopsy-proven BRPC or LAPC who received induction chemotherapy followed by RT were retrospectively enrolled. Following contouring of spleens, dose-volume histograms (DVHs) for splenic dosimetric parameters were calculated. Pre- and post-RT complete blood counts (CBC) within two weeks were recorded. Delta (Δ) values were calculated by subtracting the post-RT value from the pre-RT value. Cox regression survival analysis for pre and postradiation CBC values and OS was performed. Receiver operating curves (ROC) were generated and optimal cutoff points for highest sensitivity and specificity were identified. Kaplan-Meier curves for OS were generated. RESULTS: On univariate Cox regression analysis, the only significant CBC value associated with OS was ΔNLR (HR 1.06, CI 1.03-1.09, p < 0.001). On multivariate analysis, ΔNLR, age, and completed resection all significantly predicted for worse OS (p < 0.05). ΔNLR significantly predicted achieving surgical resection (p = 0.04) and the optimal cutoff point for ΔNLR was 2.5. Patients with ΔNLR < 2.5 had significantly longer OS (log rank p = 0.046). Spleen radiation dose parameters were all significantly higher in patients with a ΔNLR ≥ 2.5. Optimal radiation cutoff points to predict a ΔNLR ≥ 2.5 were splenic Dmean of 308 cGy and V5 of 10.3%. CONCLUSIONS: Among patients with BRPC or LAPC who have received induction chemotherapy, elevated ΔNLR after RT significantly predicts worse OS and decreased odds of achieving resection. Furthermore, ΔNLR is correlated with higher splenic doses, suggesting the spleen may be an important organ at risk.

Clinical Effectiveness of an Adaptive Treatment Planning Algorithm for Intensity Modulated Radiation Therapy Versus 3D Conformal Radiation Therapy for Node-Positive Breast Cancer Patients Undergoing Regional Nodal Irradiation/Postmastectomy Radiation Therapy.

PURPOSE: Clinical trials support adjuvant regional nodal irradiation (RNI) after breast-conserving surgery or mastectomy for patients with lymph node-positive breast cancer. Advanced treatment planning techniques (eg, intensity modulated radiation therapy [IMRT]) can reduce dose to organs at risk (OARs) in this situation. However, uncertainty persists about when IMRT is clinically indicated (vs 3-dimensional conformal radiation therapy [3DCRT]) for RNI. We hypothesized that an adaptive treatment planning algorithm (TPA) for IMRT adoption would allow OAR constraints for RNI to be met when 3DCRT could not without significantly changing toxicity and locoregional recurrence (LRR) patterns. METHODS AND MATERIALS: Since 2013, all RNI patients also underwent an adaptive TPA that began with 3DCRT and then changed to IMRT when OAR constraints (mean heart dose ≤500 cGy; ipsilateral lung V20 ≤35%) could not be met. Patients received 2 Gy/d to the prospectively contoured target volumes (including internal mammary nodes). We retrospectively evaluated the dosimetry and clinical outcomes of the treatment groups (IMRT vs 3DCRT). The primary endpoint was the cumulative incidence of LRR as the site of first recurrence, and we specifically address patterns of failure based on dose to the posterior supraclavicular nodal region (SCL-post). RESULTS: Two hundred forty patients (60% stage III; mean 4.0 + nodes) underwent an adaptive-TPA for RNI after mastectomy (74%) or breast-conserving surgery (26%), resulting in 168 patients treated with 3DCRT and 72 patients treated with IMRT. There were 7 LRRs (2 IMRT, 5 3DCRT) resulting in 4-year LRR of 2.8% for IMRT versus 1.8% for 3DCRT (P = .99). Three patients (2 IMRT, 1 3DCRT) had SCL nodal failures (1 in the SCL-post). CONCLUSIONS: An adaptive TPA for use of IMRT when 3DCRT does not meet critical OAR constraints resulted in rare high-grade toxicity and no difference in failure patterns between patients treated with IMRT and 3DCRT. These data should provide reassurance that IMRT maintains the therapeutic ratio by preserving cancer control outcomes without excess toxicity when 3DCRT fails to meet OAR constraints.

Linear accelerator-based radiosurgery is associated with lower incidence of radionecrosis compared with gamma knife for treatment of multiple brain metastases.

BACKGROUND: Gamma knife (GK) and linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) both offer excellent local control in the management of multiple brain metastases. The efficacy and toxicity of LINAC and GK SRS have not been directly compared in the modern era. We studied outcomes in patients treated with LINAC SRS and GK at two separate institutions. METHODS: We identified patients treated with either LINAC or GK who were treated to ≥2 lesions and had available follow up. LINAC patients were treated using single-isocenter multitarget technique. We used Cox regression, Fine and Gray competing risks regression, and nearest neighbor propensity score matching to account for confounders and imbalance between cohorts. Kaplan-Meier curves were used to estimate overall survival and rates of radionecrosis. RESULTS: We identified 391 patients who were treated in 537 courses to a total 2699 lesions (LINAC: 1014, GK: 1685). After propensity score matching, GK was associated with similar overall survival (HR = 0.86; 95% CI 0.59-1.24; p = 0.41) and higher rate of radionecrosis (HR = 3.83; 95% CI 1.66-8.84; p = 0.002) compared to LINAC. In a secondary propensity score matched analysis comparing radionecrosis in single-fraction LINAC and GK, GK remained associated with higher incidence of radionecrosis (HR = 4.42; 95% CI 1.28-15.29; p = 0.019). CONCLUSIONS: In this multi-institutional study, we found similar overall survival with lower incidence of radionecrosis in patients treated with LINAC compared to GK SRS. These findings are hypothesis generating and should be validated in an independent cohort.

Single-Isocenter Multitarget Stereotactic Radiosurgery Is Safe and Effective in the Treatment of Multiple Brain Metastases.

PURPOSE: Multiple studies have reported favorable outcomes for stereotactic radiosurgery (SRS) in the treatment of limited brain metastases. An obstacle of SRS in the management of numerous metastases is the longer treatment time using traditional radiosurgery. Single-isocenter multitarget (SIMT) SRS is a novel technique that permits rapid therapy delivery to multiple metastases. There is a lack of clinical evidence regarding its efficacy and safety. We report the outcomes of patients treated with this technique. METHODS AND MATERIALS: We reviewed the records of patients with intact or resected brain metastases treated with SRS in 1 to 5 fractions using SIMT technique at our institution, with at least 1 available follow-up brain magnetic resonance imaging. Survival, disease control, and toxicity were evaluated using Cox regression, logistic regression, and Kaplan-Meier analysis. RESULTS: We identified 173 patients with 1014 brain metastases. Median follow up was 12.7 months. Median beam-on time was 4.1 minutes. The median dose to the brain was 219.4 cGy. Median overall survival and freedom from intracranial progression were 13.2 and 6.3 months, respectively. Overall survival did not differ between patients treated with greater than or less than 4 lesions (hazard ratio, 1.03; 95% confidence interval 0.66-1.61; P = .91). Actuarial 1- and 2-year local control were 99.0% and 95.1%, respectively. Rates of grade 2 and grade 3 or higher radionecrosis were 1.4% and 0.9%, respectively. CONCLUSIONS: SIMT radiosurgery delivered in 1 to 5 fractions offers excellent local control and acceptable toxicity in the treatment of multiple intact and postoperative brain metastases. This technique should be evaluated prospectively.

Increasing Radiation Dose to the Thoracic Marrow Is Associated With Acute Hematologic Toxicities in Patients Receiving Chemoradiation for Esophageal Cancer.

Purpose: To test the hypothesis that increasing radiation dose to the thoracic marrow (TM) contributes to the development of hematologic toxicities (HT) in esophageal cancer (EC) patients receiving chemoradiation therapy (CRT). Methods: We identified EC cases treated with curative intent CRT at our institution from 2007 to 2016. The TM was contoured as the union of the vertebral bodies (VB) from T1-L1, the ribs from T1-L1, and the sternum. The TM-mean dose and the TM volume receiving at least 5-50 Gy (V5-V50) were collected. Grade ≥ 3 HT (HT3+) was the primary endpoint. Normal tissue complication probability (NTCP) was evaluated using the Lyman-Kutcher-Burman (LKB) model. Logistic regression was used to test associations between HT3+ and dosimetric parameters. Odds ratios (OR) and 95% confidence intervals (CI) are reported with p < 0.05 considered significant. Receiver operating characteristics analysis was used to determine optimal cut points. Results: We identified 137 EC cases, and most received concurrent carboplatin/paclitaxel (N = 83). Median radiation dose was 50.4 Gy (IQR = 50.4-50.4 Gy). The rate of HT3+ was 39.4%. Optimization of the LKB model yielded the results n = 0.70, m = 0.67, and TD50 = 20.1 Gy. The TM-V30 was most strongly associated with HT3+ and on multivariate analysis, patients with TM-V30 ≥ 14% had a 5.7-fold (95% CI 2.42-14.54, p < 0.001) increased odds of HT3+ in the entire cohort and a 4-fold (95% CI 1.54-11.11, p = 0.006) increased odds of HT3+ in the carboplatin/paclitaxel cohort compared to patients with TM-V30 < 14%. Radiation dose to the VB and rib sub-sites of the TM were also associated with HT3+, particularly VB-V40. Conclusion: We found that increasing TM radiation dose was associated with HT3+ in EC patients treated with CRT. Radiation dose to the VB and rib sub-sites were also associated with HT3+. These findings suggest that limiting radiation dose to the TM (or its sub-sites) may be sufficient to decrease HT3+, but further prospective evaluation of these results is needed.

The implementation of RapidPlan in predicting deep inspiration breath-hold candidates with left-sided breast cancer.

The aim of this study is to determine if RapidPlan (RP) can be used as a prediction method to determine which left-sided supine breast cancer patients would benefit from the deep inspiration breath-hold (DIBH) technique. An RP model database was created with 72 clinically approved 3D conformal radiation therapy (3D-CRT) treatment plans. This model was validated by introducing 10 new patient data sets, creating RP-generated plans and comparing the clinically approved plan for the corresponding patient. The prediction ability of the model was then tested on the free-breathing (FB) scans of patients with clinically approved DIBH plans totaling 29 patients and results were then compared to the FB clinical plan attempts. A statistical analysis performed on the data indicated a strong correlation for the mean heart dose (R2 = 0.914; p-value < 0.001) with a standard deviation of 48.6 cGy. After validating the link between physician PTV and mean heart dose, the model was tested clinically on 15 patients by inserting "Test PTV Evals" that were contoured by the researchers as a surrogate for predicting mean heart dose. Statistical analysis showed a strong correlation between the dose to 5% of the heart (D5) and the mean heart dose (R2 values of 0.913 and 0.881, respectively) with a standard deviation for the mean heart dose of 27.2 cGy. It was concluded that by using a Test PTV Eval, the RP-generated plans were able to predict mean heart doses within ± 30.0 cGy.

Radiation Dose to the Thoracic Vertebral Bodies Is Associated With Acute Hematologic Toxicities in Patients Receiving Concurrent Chemoradiation for Lung Cancer: Results of a Single-Center Retrospective Analysis.

PURPOSE: To test the hypothesis that increasing radiation therapy (RT) dose to the thoracic vertebral bodies (TVBs) contributes to the development of hematologic toxicities (HTs) in patients with lung cancer. METHODS AND MATERIALS: Cases of non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) treated with definitive chemoradiation with concurrent platinum-based doublet chemotherapy at our institution from 2007 to 2016 were identified. Mean TVB dose and the volume of TVBs receiving at least 5 to 60 Gy (V5-V60) were retrospectively recorded. Logistic regression was used to test associations between grade ≥3 HT (HT3+) and dosimetric/clinical parameters. Normal tissue complication probability was evaluated using the Lyman-Kutcher-Burman (LKB) model for HT3+, and receiver operating characteristics analysis was used to determine dosimetric cut-points. RESULTS: We identified 201 patients, the majority having NSCLC (n=162, 81%) and stage III to IV disease (n=179, 89%). All patients received either cisplatin/etoposide (n=107, 53%) or carboplatin/paclitaxel (n=94, 47%). Median RT dose was 60 Gy (range, 60-70 Gy). The rate of HT3+ was 49% (n=99). Increasing mean TVB dose (per Gy) was associated with higher odds of developing HT3+ (odds ratio 1.041, 95% confidence interval 1.004-1.080, P=.032), as were increasing TVB V5 to V20. These dosimetric correlates to HT3+ persisted on multivariate analysis. Constrained optimization of the LKB model for HT3+ yielded the parameters: n=1, m=1.79, and TD50=21.4 Gy. Optimal cut-points identified were V5=65%, V10=60%, V20=50%, and mean dose=23.5 Gy. Patients with values above these cut-points had an approximately 2-fold increased risk of HT3+. CONCLUSIONS: We found that mean TVB dose and low-dose parameters (V5-V20) were associated with HT3+ in chemoradiation for lung cancer. Per the LKB model, bone marrow behaves like a parallel organ (n=1), implying that mean TVB dose is a useful predictor for toxicity. These data suggest that efforts to spare dose to the TVBs may reduce rates of severe HT.

Likelihood of unacceptable normal tissue doses in breast cancer patients undergoing regional nodal irradiation in routine clinical practice.

PURPOSE: As indications for regional nodal irradiation (RNI) for breast cancer have expanded, so too has scrutiny over potential late toxicity from radiotherapy. This emphasizes the need for careful radiation treatment planning to maximize the therapeutic ratio. We sought to evaluate how often unacceptable doses (UDs) to organs at risk (OARs) occur and the associated factors for patients receiving RNI in daily practice. METHODS AND MATERIALS: Treatment records of patients who received RNI from February 2012 to May 2015 were studied. The NSABP B51/RTOG 1304 clinical dose-volume constraints for targets/OARs receiving RNI were used as the benchmark. Dose-volume histograms were analyzed for the rate of ≥1 UD delivered to the following organs: heart, mean >5 Gy; ipsilateral lung, V20 >35%, V10 >60%, V5 >70%; contralateral lung (CL), V5 >15%; and contralateral breast, V4.1 >5%. Logistic regression was used to test the association between UDs to OAR and key variables. RESULTS: Two hundred three consecutive cases received RNI (105 left, 98 right), to the chest wall in 171 (84%) and to the internal mammary nodes in 170 (84%); 77.4% of cases met all OAR constraints. The most common OAR UDs were delivered to the contralateral breast (n = 32, 15.7%) and ipsilateral lung V5 (n = 22, 10.8%). On multivariate analysis, use of intensity modulated radiation therapy (odds ratio [OR], 64.7; 95% confidence interval, 20.8-201.5; P < .001) and use of nodal boost (OR, 5.5; 95% confidence interval, 1.1-27.1; P = .04), but not internal mammary node irradiation (OR, 2.7; P = .35) or reconstruction (OR, 0.62; P = .33), were independently associated with higher OAR UD rate. For 3-dimensional conformal radiation therapy plans, 7.9% had OAR UDs. CONCLUSION: The OAR UD rate with 3-dimensional conformal radiation therapy ± deep inspiration breath-hold in routine clinical practice is low and not independently associated with internal mammary node irradiation or reconstruction presence. Women treated with intensity modulated radiation therapy had a significantly higher overall OAR UD rate, and clinicians should be aware of this as they initiate RNI treatment planning.