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Accurate target delineation/contouring is essential for radiation treatment planning and the clinical efficacy of radiation therapy. Clinical trial data has demonstrated the importance of quality contouring and treatment planning for optimal survival outcomes. As a result, improving the quality of target delineation is an important goal in the education of radiation oncology residents. However, there is limited quantitative data on the quality of residents' contours. Therefore, it would be beneficial to track performance and improvement in resident target delineation during residency. The purpose of this study was to determine if it was feasible to track the concordance of radiation oncology residents' contours with faculty physicians' contours. Residents were asked to contour target volumes (GTV, CTV, ITV, PTV, etc.) based on patient history, physical exam, clinical stage and fused diagnostic imaging and were allowed to use any available outside resources, including textbooks, review articles, consensus guidelines, and online atlases. Resident contours were saved as separate structures. Finalized, faculty physician-approved contours were also saved. Saved contour structures and data from October 2019 through June 2020 were reviewed for feasibility. In total, 209 structures had both resident and faculty versions saved within Eclipse and were available for analysis. The Boolean Operations Tool in Eclipse (Varian Medical Systems, Palo Alto, CA, USA) was used to create an intersection volume of the resident/faculty contours. Separately, the Boolean Operations Tool was used to create a union volume of the resident/faculty contours. Based on these two volumes, the Jaccard Concordance Index (JCI) was calculated by dividing the intersection volume (in cubic centimeters [cc]) by the union volume (cc). The JCI could be successfully calculated for 203 (97.1%) of the 209 structures. For 6 structures (2.9%), both the intersection and union volumes could not be calculated because the volumes were too small for Eclipse to determine. All 6 of these structures were small brain metastases. Tracking and comparing the concordance of resident contours and faculty physician contours is feasible using available tools in Eclipse. Additional data collection and assessment is necessary before this technique can be more widely utilized. [ABSTRACT FROM AUTHOR]

• Many head/neck squamous cell cancer patients develop recurrence or second primary. • Re-irradiation is a curative treatment option for these patients. • However, it is associated with significant risk of toxicity. • Pulsed Reduced Dose Rate radiation may reduce re-irradiation toxicity. Pulsed reduced dose rate (PRDR) radiation (RT) is a re-irradiation (Re-RT) technique that potentially overcomes dose/volume constraints in the setting of previous RT. There is minimal data for its use for recurrent or secondary primary head and neck squamous cell carcinoma (HNSCC). In this study, we report preliminary data from our institution of a consecutive cohort of HNSCC patients who received PRDR Re-RT. Nine patients received PRDR Re-RT from August 2020 to January 2023 and had analyzable data. Intensity modulated RT was used for treatment delivery and a wait time between 20 cGy arc/helical deliveries was used to achieve the effective low dose rate. Data collected included patient demographic information, prior interventions, diagnosis, radiation therapy dose and fractionation, progression free survival, overall survival, and toxicity rates. The median time to PRDR-RT from completion of initial RT was 13 months (range, 6–50 months). All but one patient underwent salvage surgery prior to PRDR-RT. The median follow-up after Re-RT was 7 months. The median OS from PRDR-RT was 7 months (range, 1–32 months). Median PFS was 7 months (range, 1–32 months). One patient (11.1 %) had acute grade 3 toxicity, and two patients (22.2 %) had late grade 3 toxicities. There were no grade 4+ toxicities. PRDR Re-RT is a feasible treatment strategy for patients with recurrent or second primary HNSCC. Initial findings from this retrospective review suggest reasonable survival outcomes and potentially improved toxicity; prospective data is needed to establish the safety and efficacy of this technique. [ABSTRACT FROM AUTHOR]