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Purpose/Objectives To determine the utilization of and barriers to implementation of radiopharmaceutical therapy (RPT) amongst U.S. radiation oncologists. Materials/Methods An anonymous, voluntary 21-item survey directed towards attending radiation oncologists was distributed via social media platforms (Twitter, LinkedIn, Facebook, Student Doctor Network). Questions assessed practice characteristics, specific RPT prescribing patterns, RPT prescribing interest, and perceived barriers to RPT implementation. Non-parametric χ2 test was used for correlation statistics. Results Of the 142 respondents, 131 (92.3%) practiced in the U.S. and were included for this analysis. Respondents were well balanced in terms of practicing region, population size served, practice setting and years in practice. Forty-eight percent (n=63) reported prescribing at least one RPT. An additional 7% (n=8) participate in RPT administration without billing themselves. Among those that actively prescribed RPT, the mean cumulative cases per month was 4.2 (range: 1-5). The most commonly prescribed radionuclides were Radium-223 (40%; mean 2.8 cases/month), Iodine-131 (18%; mean 2.3 cases/month), Yttrium-90 (13%; mean 3.4 cases/month), “other” (8%), Samarium-153 (6%; mean 1.0 cases/month), Strontrium-89 and Phosphorous-32 (2% each; mean 1.8 and 0.4 cases/month respectively). Of those who answered “other”, Lutetium-177 dotatate was most commonly prescribed (8%). No significant (p Most radiation oncologists (56%, n=74) responded they would like to actively prescribe more RPT, while 27% (n=35) were indifferent and 17% (n=22) answered “no.” Perceived barriers to implementation were varied but broadly categorized into treatment infrastructure (44%, n=57), inter-specialty relations (41%, n=53), lack of training (23%, n=30), and financial considerations (16%, n=21). Conclusion Among surveyed U.S. radiation oncologists, a significant number reported prescribing at least one RPT. The majority expressed interest in prescribing additional RPT. Wide-ranging barriers to implementation exist, most commonly inter-specialty relations, treatment infrastructure, lack of training, and financial considerations.

Purpose Dose to normal lung has commonly been linked with radiation-induced lung toxicity (RILT) risk, but incorporating functional lung metrics in treatment planning may help further optimize dose delivery and reduce RILT incidence. The purpose of this study was to investigate the impact of the dose delivered to functional lung regions by analyzing perfusion (Q), ventilation (V), and combined V/Q single-photon-emission computed tomography (SPECT) dose-function metrics with regard to RILT risk in patients with non-small cell lung cancer (NSCLC) patients who received radiation therapy (RT). Methods and Materials SPECT images acquired from 88 patients with locally advanced NSCLC before undergoing conventionally fractionated RT were retrospectively analyzed. Dose was converted to the nominal dose equivalent per 2 Gy fraction, and SPECT intensities were normalized. Regional lung segments were defined, and the average dose delivered to each lung region was quantified. Three functional categorizations were defined to represent low-, normal-, and high-functioning lungs. The percent of functional lung category receiving ≥20 Gy and mean functional intensity receiving ≥20 Gy (iV20) were calculated. RILT was defined as grade 2+ radiation pneumonitis and/or clinical radiation fibrosis. A logistic regression was used to evaluate the association between dose-function metrics and risk of RILT. Results By analyzing V/Q normalized intensities and functional distributions across the population, a wide range in functional capability (especially in the ipsilateral lung) was observed in patients with NSCLC before RT. Through multivariable regression models, global lung average dose to the lower lung was found to be significantly associated with RILT, and Q and V iV20 were correlated with RILT when using ipsilateral lung metrics. Through a receiver operating characteristic analysis, combined V/Q low-function receiving ≥20 Gy (low-functioning V/Q20) in the ipsilateral lung was found to be the best predictor (area under the curce: 0.79) of RILT risk. Conclusions Irradiation of the inferior lung appears to be a locational sensitivity for RILT risk. The multivariable correlation between ipsilateral lung iV20 and RILT, as well as the association of low-functioning V/Q20 and RILT, suggest that irradiating low-functioning regions in the lung may lead to higher toxicity rates.