Comparison of standardized uptake value-based positron emission tomography and computed tomography target volumes in esophageal cancer patients undergoing radiotherapy.
OBJECTIVE
To study various standardized uptake value (SUV)-based approaches to ascertain the best strategy for delineating metabolic tumor volumes (MTV).


METHODS
Twenty-two consecutive previously treated esophageal cancer patients with positron emission tomography (PET) imaging and computed tomography (CT)-based radiotherapy plans were studied. At the level of the tumor epicenter, MTVs were delineated at 11 different thresholds: SUV ≥2, ≥2.5, ≥3, ≥3.5 (SUV(n)); ≥40%, ≥45%, and ≥50% of the maximum (SUV(n%)); and mean liver SUV + 1, 2, 3, and 4 standard deviations (SUV(Lnσ)). The volume ratio and conformality index were determined between MTVs, and the corresponding CT/endoscopic ultrasound-based gross tumor volume (GTV) at the epicenter. Means were analyzed by one-way analysis of variance for repeated measures and further compared using a paired t test for repeated measures.


RESULTS
The mean conformality indices ranged from 0.33 to 0.48, being significantly (p < 0.05) closest to 1 at SUV(2.5) (0.47 ± 0.03) and SUV(L4σ) (0.48 ± 0.03). The mean volume ratios ranged from 0.39 to 2.82, being significantly closest to 1 at SUV(2.5) (1.18 ± 0.36) and SUV(L4σ) (1.09 ± 0.15). The mean value of the SUVs calculated using the SUV(L4σ) approach was 2.4.


CONCLUSIONS
Regardless of the SUV thresholding method used (i.e., absolute or relative to liver mean), a threshold of approximately 2.5 yields the highest conformality index and best approximates the CT-based GTV at the epicenter. These findings may ultimately aid radiation oncologists in the delineation of the entire GTV in esophageal cancer patients.
Vali
Faisal S
FS
Department of Radiation Oncology, Loyola University Medical Center, Maywood, IL 60153, USA.
Nagda
Suneel
S
Hall
William
W
Sinacore
James
J
Gao
Mingcheng
M
Lee
Steven H
SH
Hong
Robert
R
Shoup
Margaret
M
Emami
Bahman
B
D000704:Analysis of Variance; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000532:radiotherapy; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000378:metabolism; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden; D018084:Ultrasonography, Interventional / Q000379:methods
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18