An assessment of skill erosion on high‐dose rate brachytherapy treatment planning

Purpose To assess skill erosion for physicists after leaving brachytherapy service and contributors to variability during brachytherapy treatment planning. Methods Medical physicists simulated planning for nine patients by creating treatment plans twice, 2 months apart. The physicists were stratified as “On‐Service” if they were assigned to and actively participating in the brachytherapy service (including treatment planning) during the study or “Off‐Service” if they were not assigned, were not actively engaged in the service, and had not performed treatment planning the 6 months prior to the study commencement or during the study. A mixed effects model with Bonferroni correction was used to test for statistical significance between the stratified groups and Cohen's D was used to compare the effect of skill erosion. ANOVA analysis of a crossed Gauge Repeatability and Reproducibility (Gauge R&R) study quantified three contributors to variability for eight segments of the planning process: [1] repeatability (intra‐observer), [2] reproducibility (inter‐observer), and [3] patient‐to‐patient variation. Process capability was deemed acceptable when the Total Gauge R&R was less than 10%, marginally acceptable between 10% and 30%, and unacceptable when greater than 30%. Results The group of On‐Service study participants had lower variability on 10 of 19 measures in the brachytherapy planning process than Off‐Service study participants with the effect size being small, Cohen's D between 0.15 and 0.30 for significant measures. This indicates skill erosion does affect physicists after leaving the brachytherapy service for a period of 6 months or more. For both groups, only the bladder D2cc metric had a controlled amount of variability other than applicator reconstruction. Conclusions Brachytherapy treatment planning suffers from skill erosion. Physicists should seek to mitigate its effects and evaluate competency on an ongoing basis.