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Inter‐scan and inter‐observer tumour volume delineation variability on cone beam computed tomography in patients treated with stereotactic body radiation therapy for early‐stage non‐small cell lung cancer
Author(s) -
Hou Ying,
Lee Stephanie,
Agrawal Vishesh,
Romano John,
Baldini Elizabeth H,
Chen Aileen B,
Kozono David E,
Killoran Joseph H,
Wagar Matthew,
Hacker Fred L,
Aerts Hugo JWL,
Lewis John H,
Mak Raymond H
Publication year - 2017
Publication title -
journal of medical imaging and radiation oncology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.31
H-Index - 43
eISSN - 1754-9485
pISSN - 1754-9477
DOI - 10.1111/1754-9485.12537
Subject(s) - medicine , computed tomography , stage (stratigraphy) , cone beam computed tomography , radiation therapy , radiology , nuclear medicine , lung cancer , oncology , paleontology , biology
Quantification of volume changes on cone beam computed tomography ( CBCT ) during lung stereotactic body radiation therapy ( SBRT ) for non‐small cell lung cancer ( NSCLC ) may provide a useful radiological marker for radiation response and for adaptive treatment planning. This study quantifies inter‐scan and inter‐observer variability in tumour volume delineation on CBCT . Methods Three clinicians independently contoured the primary gross tumour volume ( GTV ) manually on CBCT s taken immediately before SBRT treatment (pre) and after the same SBRT treatment (post) for 19 NSCLC patients. Relative volume differences ( RVD ) were calculated between the pre‐ and post‐ CBCT s for a given treatment and between any two of three observers for a given CBCT . Coefficient of variation ( CV ) was used to quantitatively measure and compare the extent of variability. Results Inter‐observer variability had a significantly higher CV of 0.15 ± 0.13 compared to inter‐scan CV of 0.03 ± 0.04 with P < 0.0001. The greatest variability was observed with tumours (<2 cm in diameter) versus larger tumours with 95% limit of agreement ( LOA ) (Mean ± Standard Deviation) of 1.90% ± 19.55% vs. −0.97% ± 12.26% for inter‐scan RVD and 29.99% ± 73.84% vs. 9.37% ± 29.95% for inter‐observer RVD respectively. Conclusions Inter‐observer variability was greater than inter‐scan variability for tumour volume delineation on CBCT with greatest variability for small tumours (<2 cm in diameter). LOA for inter‐scan variability (~12%) helps defines a threshold for clinically meaningful tumour volume change during SBRT treatment for tumours with diameter greater than 2 cm, with larger thresholds needed for smaller tumours.