Delineation in thoracic oncology: a prospective study of the effect of training on contour variability and dosimetric consequences

Abstract

IntroductionAs part of French residents' radiotherapy training, delineation workstations were available at a national teaching course. We report a prospective comparative study of a non small cell lung cancer (NSCLC) case delineated by 120 residents before and after a radioanatomy/radiotherapy lecture.Materials and methodsThe case of a patient with right upper lobe non small cell lung cancer (NSCLC) was provided for delineation to 32 groups of residents before and after a radiation therapy lecture about thoracic delineation. GTV, CTV and PTV was asked to each group. In a second step, the GTV, CTV and PTV were compared with those of 9 groups of senior physicians. Finally the consequences for treatment planning between each group before and after the course were explored.ResultsThe expert's average GTV, CTV and PTV were 89.1 cm3, 242.3 cm3 and 293.9 cm3 respectively. For residents, those volumes were 103.4 cm3, 242.3 cm3 and 457.9 cm3 before teaching, compared to 99.5 cm3, 224.2 cm3 and 412.5 cm3 after teaching. The overlap (OV) and kappa (KI) indices before and after education were respectively 0.58 and 0.73. Compared to senior physicians, OV and KI indices were lower in the residents group (p = 0.039 and p = 0.043). An increased dose to the lung is noted for the residents' dosimetry compared to the experts' (V20: 23.2% versus 36.5%) due to the larger PTV delineated. No significant difference was observed for other organs at risk.ConclusionThere were no significant differences for the delineation of the GTV and CTV before and after the course, although the differences tended to decrease after the course. The good initial quality of the contours could explain the lack of difference. V20 for lung was higher in the residents group compared to the experts group (23.2% vs 36.5%). No other treatment planning consequences were observed for other critical organs.

Variabilities of Magnetic Resonance Imaging–, Computed Tomography–, and Positron Emission Tomography–Computed Tomography–Based Tumor and Lymph Node Delineations for Lung Cancer Radiation Therapy Planning

“…The causes of this might be multifactorial. Observer training had been shown to reduce contouring variability [40, 41]. In this study, for each patient, graphical information on the location of the primary tumor and lymph nodes of interest was provided to minimize contouring errors due to uncertainty about tumor position and to focus the study on the detection of uncertainties arising from differences in imaging modalities only.…”

Conformity analysis to demonstrate reproducibility of target volumes for Margin-Intense Stereotactic Radiotherapy for borderline-resectable pancreatic cancer

“…SPARC incorporates a comprehensive radiotherapy quality assurance programme to ensure consistency in target definition and radiotherapy delivery. This includes a radiotherapy manual with atlas, and pre-trial contouring and planning test-cases followed by a workshop, both of which have been shown to reduce variation in target volume definition [13], [14], [15]. The radiotherapy manual specifies that the target structure for the margin-directed boost should be defined following discussion with the radiologist and/or Hepato-Pancreato-Biliary (HPB) surgeon to identify the vascular structures that are responsible for the tumour being classified as borderline resectable according to the NCCN criteria.…”

Contouring experiences amongst Australian, New Zealand and Singaporean radiation oncology trainees. Is it enough? What next?

“…Radiation therapy (RT) planning is a fundamental part of clinical practice. Contouring or target volume delineation is a potential source of error in RT planning and is the skill set with the greatest inter‐observer variability . In addition, the ability to critically appraise RT plans to ensure the optimal plan for each patient is central to the practice of a Radiation Oncologist.…”