Peer review quality assurance in stereotactic body radiotherapy planning: The impact of case volume

Purpose: Peer review is an essential quality assurance component of radiation therapy planning. A growing body of literature has demonstrated substantial rates of suggested plan changes resulting from peer review. There remains a paucity of data on the impact of peer review rounds for stereotactic body radiation therapy (SBRT). We therefore aim to evaluate the outcomes of peer review in this specific patient cohort. Methods and materials: We conducted a retrospective review of all SBRT cases that underwent peer review from July 2015 to June 2018 at a single institution. Weekly peer review rounds are grouped according to cancer subsite and attended by radiation oncologists, medical physicists and medical radiation technologists. We prospectively compiled 'learning moments', defined as cases with suggested changes or where an educational discussion occurred beyond routine management, and critical errors, defined as errors which could alter clinical outcomes, recorded prospectively during peer review. Plan changes implemented after peer review were documented. Results: Nine hundred thirty-four SBRT cases were included. The most common treatment sites were lung (518, 55%), liver (196, 21%) and spine (119, 13%). Learning moments were identified in 161 cases (17%) and translated into plan changes in 28 cases (3%). Two critical errors (0.2%) were identified: An inadequate planning target volume margin and an incorrect image set used for contouring. There was a statistically significantly higher rate of learning moments for lower-volume SBRT sites (defined as ≤30 cases/year) versus higher-volume SBRT sites (29% vs 16%, respectively; p = 0.001). Conclusions: Peer review for SBRT cases revealed a low rate of critical errors, but did result in implemented plan changes in 3% of cases, and either educational discussion or suggestions of plan changes in 17% of cases. All SBRT sites appear to benefit from peer review, though lower-volume sites may require particular attention.