Contour variation is a primary source of error when delivering post prostatectomy radiotherapy: Results of the Trans‐Tasman Radiation Oncology Group 08.03 Radiotherapy Adjuvant Versus Early Salvage (RAVES) benchmarking exercise

Abstract

Introduction Variation in target volume delineation from clinical trial protocols has been shown to contribute to poorer patient outcomes. A clinical trial quality assurance framework can support compliance with trial protocol. Results of the TROG 08.03 RAVES benchmarking exercise considering variation from protocol, inter‐observer variability and impact on dosimetry are reported in this paper. Methods Clinicians were required to contour and plan a benchmarking case according to trial protocol. Geometric pjmirometers including volume, Hausdorff Distance, Mean Distance to Agreement and DICE similarity coefficient were analysed for targets and organs at risk. Submitted volumes were compared to a STAPLE and consensus ‘reference’ volume for each structure. Dosimetric analysis was performed using dose volume histogram data. Results Benchmarking exercise submissions were received from 96 clinicians. In total 205 protocol variations were identified. The most common variation was inadequate contouring of the CTV in 84/205 (41%). The CTV volume ranged from 65.3 to 193.1 cm3 with a median of 113.2 cm3. The most common dosimetric protocol variation related to rectal dosimetry. The mean submitted rectal volume receiving 40 Gy and 60 Gy, respectively, was 56.14% ± 5.55% and 30.25% ± 6.15%. When corrected to the protocol defined length the mean rectal volume receiving 40 Gy was 60.8% ± 7.92%, while the volume receiving 60 Gy was 33.86% ± 8.21%. Conclusion Variations from protocol were found in the RAVES benchmarking exercise, most notably in CTV and rectum delineation. Inter‐observer variability was evident. Incorrect delineation of the rectum impacted on dosimetric compliance with protocol.

Autosegmentation based on different-sized training datasets of consistently-curated volumes and impact on rectal contours in prostate cancer radiation therapy

“…In RT, differences in OAR volumes do not always translate into large dose differences [9] , [21] although compliance to trial protocols have been reported to be compromised due to incorrect delineations [2] . We found in our data that autosegmented rectal volumes, irrespective of algorithm version, were overall closer to the manually-delineated uncurated clinical rectal volumes (Δ≈0.5–1 cm 3 ) than to the manually-delineated curated rectal volumes (Δ≈1-3 cm 3 ), with the larger differences typically generated by the smaller-sized training datasets.…”

“…In radiation therapy (RT), contour/volume variability continues to be a problem, in particular for non-tumour tissue or organs at risk (OARs) [1] , [2] , [3] , [4] , [5] . Dose fall-off margins in modern RT can be set extremely tight meaning that correct volume definitions are more critical now compared with previous RT delivery techniques.…”

Variability of Target Volumes and Organs at Risk Delineation in Breast Cancer Radiation Therapy: Quality Assurance Results of the Pretrial Benchmark Case for the POTENTIAL Trial

“…[3][4][5] Contouring variation is a common weakness in RT trials. [6][7][8] Marked variations in target volumes and organ-at-risk (OAR) delineations for breast cancer have been reported. 9,10 Computed tomography (CT)−based RT planning for breast cancer has not been applied widely until recent years; therefore, studies on pretrial target delineation QA in breast cancer are limited, 11,12 and no slice-by-slice analysis has been undertaken to identify the details of contouring variation.…”

Implementation of web-based open-source radiotherapy delineation software (WORDS) in organs at risk contouring training for newly qualified radiotherapists: quantitative comparison with conventional one-to-one coaching approach

“…Variability in contouring is deemed to be one of the greatest sources of error in medical dosimetry [6]. Previous studies have stated that variations in contouring can be occurred in health professionals with different level of experience [7][8][9].…”