401P - Inter-observer variability in the delineation of gross tumour volume GTV using PETCT in early stage non small cell lung cancer NSCLC (401P)

Date 18 November 2017
Event ESMO Asia 2017 Congress
Session Poster lunch
Topics Non-Small-Cell Lung Cancer, Early Stage
Imaging, Diagnosis and Staging
Presenter Mangesh Patil
Citation Annals of Oncology (2017) 28 (suppl_10): x119-x121. 10.1093/annonc/mdx669
Authors M.B. Patil1, J.P. Agarwal1, A.R. Tibdewal1, A. Chatterji1, N. Purandare2, V. Rangrajan2
  • 1Radiation Oncology, Tata Memorial Hospital, Mumbai, 400012 - Mumbai/IN
  • 2Nuclear Medicine, Tata Memorial Hospital, Mumbai, 400012 - Mumbai/IN

Abstract

Background

Inter-observer variability in contouring is a well-known phenomenon in radiotherapy. The purpose of the study was to evaluate the magnitude of interobserver variability in the delineation of gross tumour volume 9GTV) using 18F‐Fluorodeoxyglucose positron emission tomography‐computed tomography (18F‐FDG‐PET‐CT) in early stage non small cell lung cancer.

Methods

From January 2013‐ July 2014, 20 consecutive patients with diagnosed early NSCLC (pT1‐pT3, N0M0) were accrued. The GTV was drawn in three dimensions on CT scan images as visualized by a radiation oncologist (RO) with the simultaneous incorporation of information from PET images. The GTV was drawn independently for each patient by 3 radiation oncologists with varying degree of experience (RO A- 2 years, RO B – 5 years, and RO C- more than 10 years). The GTVs delineated by three different observers were compared by the concordance index (CI), defined as the ratio of the intersection and the union of the two volumes (CI = (A∩B)/(AUB) in which A stands for the GTV of the first observer and B for the GTV of the second observer). The concordance indices were calculated for observer A vs. B, B vs. C, A vs. C in each patient.

Results

Mean GTV of 20 patients for observer A, B, and C were 93.2 cubic centimeters (ccs), 89.3 ccs, and 92.4 ccs respectively. Mean CI for observer A vs. B, A vs. C and B vs. C were 0.819, 0.802 and 0.801 respectively. On comparison using Wilcoxon-signed rank test, mean CIs between three pairs were not significantly different statistically (p-value for A vs. B and A vs. C is 0.548, p-value for A vs. B and B vs. C is 0.666, p-value for A vs. C and B vs. C is 0.638). On overall comparison by Friedman test, mean CIs between three pairs were not significantly different statistically (p-value 0.681).

Conclusions

We found that there exists a good agreement in the delineation of GTV using PETCT for early stage non small cell lung cancer between three radiation oncologists despite the difference in the degree of experience.

Clinical trial identification

Legal entity responsible for the study

Tata Memorial Hospital

Funding

None

Disclosure

All authors have declared no conflicts of interest.