A Comparative Risk Analysis of Cone Beam Computed Tomography-based Daily Adaptive Radiation Therapy and Cone Beam Computed Tomography-based Radiation Therapy Alone

Abstract

Purpose: When adopting a new therapeutic technology, a comparison to a standard of care is needed. We aim to directly compare the specific safety implications of adaptive radiation therapy (ART) to those of traditional image guided radiation therapy (IGRT), as implemented on a ring gantry linear accelerator with kilovoltage cone beam computed tomography-based online ART capability.

Methods and materials: An interdisciplinary committee performed a failure modes and effects analysis based on the American Association of Physicists in Medicine (AAPM) Task Group 100 method addressing initial treatment planning, quality assurance, and treatment delivery for both IGRT-alone and IGRT with ART on the Varian Ethos. Failure modes were categorized by process step and associated clinical roles, scored by severity, occurrence, and detectability, and ranked by risk priority number (RPN). Failure modes shared by IGRT and ART were scored and analyzed comparatively.

Results: We identified 33 unique system failure modes as part of the IGRT-alone workflow, and 9 additional failure modes specific to ART. Most high-risk IGRT-alone system failure modes were associated with initial treatment planning errors. High-risk ART failure modes also included errors related to adaptive replanning. Reanalysis of 33 IGRT-alone failure modes in the ART setting found an overall decrease in median RPN from 96 (IQR, 56-144) to 72 (IQR, 32-120; P = .035). RPN decreased for 12 failure modes, with the greatest change observed among the highest-ranked failure modes for IGRT-alone.

Conclusions: Although online ART introduces new avenues for error in the adaptive replanning process, the enhanced staffing and iterative plan review reduce the risk associated with systematic errors originating in initial treatment planning. The finding that the RPN decreased in the adaptive setting provides a unique motivation for the adoption of ART from a patient safety perspective, beyond the well-documented dosimetric benefit of ART.