The impact of organ-at-risk contour variations on automatically generated treatment plans for NSCLC

Femke Vaassen; Colien Hazelaar; Richard Canters; Stephanie Peeters; Steven Petit; Wouter van Elmpt

doi:10.1016/j.radonc.2021.08.014

The impact of organ-at-risk contour variations on automatically generated treatment plans for NSCLC

Radiother Oncol. 2021 Oct:163:136-142. doi: 10.1016/j.radonc.2021.08.014. Epub 2021 Aug 27.

Authors

Femke Vaassen¹, Colien Hazelaar², Richard Canters², Stephanie Peeters², Steven Petit³, Wouter van Elmpt²

Affiliations

¹ Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, The Netherlands. Electronic address: femke.vaassen@maastro.nl.
² Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, The Netherlands.
³ Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.

PMID: 34461185
DOI: 10.1016/j.radonc.2021.08.014

Abstract

Background and purpose: Quality of automatic contouring is generally assessed by comparison with manual delineations, but the effect of contour differences on the resulting dose distribution remains unknown. This study evaluated dosimetric differences between treatment plans optimized using various organ-at-risk (OAR) contouring methods.

Materials and methods: OARs of twenty lung cancer patients were manually and automatically contoured, after which user-adjustments were made. For each contour set, an automated treatment plan was generated. The dosimetric effect of intra-observer contour variation and the influence of contour variations on treatment plan evaluation and generation were studied using dose-volume histogram (DVH)-parameters for thoracic OARs.

Results: Dosimetric effect of intra-observer contour variability was highest for Heart D_max (3.4 ± 6.8 Gy) and lowest for Lungs-GTV D_mean (0.3 ± 0.4 Gy). The effect of contour variation on treatment plan evaluation was highest for Heart D_max (6.0 ± 13.4 Gy) and Esophagus D_max (8.7 ± 17.2 Gy). Dose differences for the various treatment plans, evaluated on the reference (manual) contour, were on average below 1 Gy/1%. For Heart D_mean, higher dose differences were found for overlap with PTV (median 0.2 Gy, 95% 1.7 Gy) vs. no PTV overlap (median 0 Gy, 95% 0.5 Gy). For D_max-parameters, largest dose difference was found between 0-1 cm distance to PTV (median 1.5 Gy, 95% 4.7 Gy).

Conclusion: Dose differences arising from automatic contour variations were of the same magnitude or lower than intra-observer contour variability. For Heart D_mean, we recommend delineation errors to be corrected when the heart overlaps with the PTV. For D_max-parameters, we recommend checking contours if the distance is close to PTV (<5 cm). For the lungs, only obvious large errors need to be adjusted.

Keywords: Automatic contouring; Automatic planning; Delineation inaccuracies; Dosimetric differences; Intra-observer variability; Radiotherapy.

MeSH terms

Carcinoma, Non-Small-Cell Lung* / radiotherapy
Humans
Lung Neoplasms* / radiotherapy
Organs at Risk
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Intensity-Modulated*