PET-based delineation of tumour volumes in lung cancer: comparison with pathological findings
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The objective of the study was to validate an adaptive, contrast-oriented thresholding algorithm (COA) for tumour delineation in 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) for non-small cell lung cancer (NSCLC) in comparison with pathological findings. The impact of tumour localization, tumour size and uptake heterogeneity on PET delineation results was also investigated.
PET tumour delineation by COA was compared with both CT delineation and pathological findings in 15 patients to investigate its validity. Correlations between anatomical volume, metabolic volume and the pathology reference as well as between the corresponding maximal diameters were determined. Differences between PET delineations and pathological results were investigated with respect to tumour localization and uptake heterogeneity.
The delineated volumes and maximal diameters measured on PET and CT images significantly correlated with the pathology reference (both r > 0.95, p < 0.0001). Both PET and CT contours resulted in overestimation of the pathological volume (PET 32.5 ± 26.5 %, CT 46.6 ± 27.4 %). CT volumes were larger than those delineated on PET images (CT 60.6 ± 86.3 ml, PET 48.3 ± 61.7 ml). Maximal tumour diameters were similar for PET and CT (51.4 ± 19.8 mm for CT versus 53.4 ± 19.1 mm for PET), slightly overestimating the pathological reference (mean difference CT 4.3 ± 3.2 mm, PET 6.2 ± 5.1 mm). PET volumes of lung tumours located in the lower lobe were significantly different from those determined from pathology (p = 0.037), whereas no significant differences were observed for tumours located in the upper lobe (p = 0.066). Only minor correlation was found between pathological tumour size and PET heterogeneity (r = −0.24).
PET tumour delineation by COA showed a good correlation with pathological findings. Tumour localization had an influence on PET delineation results. The impact of tracer uptake heterogeneity on PET delineation should be considered carefully and individually in each patient. Altogether, PET tumour delineation by COA for NSCLC patients is feasible and reliable with the potential for routine clinical application.
KeywordsVolume delineation 18F-FDG PET Lung cancer Radiotherapy Pathology
We gratefully acknowledge the valuable support of Dipl. Ing. P. Donsch in the preparation of the phantoms.
Conflicts of interest
- 1.Hicks RJ, Kalff V, MacManus MP, Ware RE, Hogg A, McKenzie AF, et al. (18)F-FDG PET provides high-impact and powerful prognostic stratification in staging newly diagnosed non-small cell lung cancer. J Nucl Med 2001;42(11):1596–604.Google Scholar
- 5.Bradley J, Bae K, Choi N, Forster K, Siegel BA, Brunetti J, et al. A phase II comparative study of gross tumor volume definition with or without PET/CT fusion in dosimetric planning for non-small-cell lung cancer (NSCLC): primary analysis of Radiation Therapy Oncology Group (RTOG) 0515. Int J Radiat Oncol Biol Phys 2012;82(1):435–441.e1.PubMedCrossRefGoogle Scholar
- 18.Schaefer A, Kremp S, Hellwig D, Rübe C, Kirsch CM, Nestle U. A contrast-oriented algorithm for FDG-PET-based delineation of tumour volumes for the radiotherapy of lung cancer: derivation from phantom measurements and validation in patient data. Eur J Nucl Med Mol Imaging 2008;35(11):1989–99.PubMedCrossRefGoogle Scholar
- 22.Schaefer A, Nestle U, Kremp S, Hellwig D, Grgic A, Buchholz HG, et al. Multi-centre calibration of an adaptive thresholding method for PET-based delineation of tumour volumes in radiotherapy planning of lung cancer. Nuklearmedizin 2012;51(3):101–10.Google Scholar
- 23.Turkington TG, DeGrado T, Sampson WH. Small spheres for lesion detection phantoms. IEEE Nucl Sci Symp Conf Rec 2001;4–10:2234–7.Google Scholar
- 26.Grgic A, Ballek E, Fleckenstein J, Moca N, Kremp S, Schaefer A, et al. Impact of rigid and nonrigid registration on the determination of 18F-FDG PET-based tumour volume and standardized uptake value in patients with lung cancer. Eur J Nucl Med Mol Imaging 2011;38(5):856–64.PubMedCrossRefGoogle Scholar
- 27.van Baardwijk A, Bosmans G, Boersma L, Buijsen J, Wanders S, Hochstenbag M, et al. PET-CT-based auto-contouring in non-small-cell lung cancer correlates with pathology and reduces interobserver variability in the delineation of the primary tumor and involved nodal volumes. Int J Radiat Oncol Biol Phys 2007;68(3):771–8.PubMedCrossRefGoogle Scholar
- 34.Nestle U, Kremp S, Schaefer-Schuler A, Sebastian-Welsch C, Hellwig D, Rübe C, et al. Comparison of different methods for delineation of 18F-FDG PET-positive tissue for target volume definition in radiotherapy of patients with non-small cell lung cancer. J Nucl Med 2005;46(8):1342–8.PubMedGoogle Scholar
- 39.Basu S, Kwee TC, Gatenby R, Saboury B, Torigian DA, Alavi A. Evolving role of molecular imaging with PET in detecting and characterizing heterogeneity of cancer tissue at the primary and metastatic sites, a plausible explanation for failed attempts to cure malignant disorders. Eur J Nucl Med Mol Imaging 2011;38(6):987–91.PubMedCrossRefGoogle Scholar