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Metabolic Tumor Volume and Total Lesion Glycolysis in Oropharyngeal Cancer Treated With Definitive Radiotherapy

Which Threshold Is the Best Predictor of Local Control?

Castelli, Joël, MD, MSc*†‡; Depeursinge, Adrien, PhD§∥; de Bari, Berardino, MD; Devillers, Anne, MD**; de Crevoisier, Renaud, MD, PhD†‡††; Bourhis, Jean, MD, PhD*; Prior, John O., MD, PhD‡‡

doi: 10.1097/RLU.0000000000001614
Original Articles
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Purpose In the context of oropharyngeal cancer treated with definitive radiotherapy, the aim of this retrospective study was to identify the best threshold value to compute metabolic tumor volume (MTV) and/or total lesion glycolysis to predict local-regional control (LRC) and disease-free survival.

Methods One hundred twenty patients with a locally advanced oropharyngeal cancer from 2 different institutions treated with definitive radiotherapy underwent FDG PET/CT before treatment. Various MTVs and total lesion glycolysis were defined based on 2 segmentation methods: (i) an absolute threshold of SUV (0–20 g/mL) or (ii) a relative threshold for SUVmax (0%–100%). The parameters’ predictive capabilities for disease-free survival and LRC were assessed using the Harrell C-index and Cox regression model.

Results Relative thresholds between 40% and 68% and absolute threshold between 5.5 and 7 had a similar predictive value for LRC (C-index = 0.65 and 0.64, respectively). Metabolic tumor volume had a higher predictive value than gross tumor volume (C-index = 0.61) and SUVmax (C-index = 0.54). Metabolic tumor volume computed with a relative threshold of 51% of SUVmax was the best predictor of disease-free survival (hazard ratio, 1.23 [per 10 mL], P = 0.009) and LRC (hazard ratio: 1.22 [per 10 mL], P = 0.02).

Conclusions The use of different thresholds within a reasonable range (between 5.5 and 7 for an absolute threshold and between 40% and 68% for a relative threshold) seems to have no major impact on the predictive value of MTV. This parameter may be used to identify patient with a high risk of recurrence and who may benefit from treatment intensification.

From the *Department of Radiation Oncology, Lausanne University Hospital, Switzerland; †INSERM, U1099, Rennes; ‡Université de Rennes 1, LTSI, Rennes, France; §Ecole Polytechnique Fédérale de Lausanne, Lausanne; and ∥University of Applied Sciences Western Switzerland, Sierre, Switzerland; ¶University Hospital Jean Minjoz, INSERM 1098, Besancon; **Nuclear Medicine Department, Centre Eugene Marquis, Rennes; ††Department of Radiation Oncology, Centre Eugene Marquis, Rennes; and ‡‡Nuclear Medicine and Molecular Imaging Department, Lausanne University Hospital, Lausanne, Switzerland.

Received for publication October 20, 2016; revision accepted January 15, 2017.

Conflicts of interest and sources of funding: This work was partly supported by the Swiss National Science Foundation with grant agreement PZ00P2_154891 (to A. Depeursinge). None declared to all other authors.

Correspondence to: Joël Castelli, MD, MSc, Department of Radiation Oncology, Centre Eugene Marquis, avenue de la Bataille Flandre Dunkerque, F-35000 Rennes, France. E-mail: j.castelli@rennes.unicancer.fr.

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