The aim of this study was to assess the prognostic significance of parameters derived from pretreatmentF-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) for patients with nasopharyngeal carcinoma (NPC) received intensity-modulated radiation therapy (IMRT). Furthermore, the functional information provided by PET/CT may offer the feasibility of biological conformality in tumor target delineation and dose planning.
We retrospectively reviewed 82 NPC patients who underwent pretreatment F-18 FDG PET/CT and received IMRT between 2010 and 2013. Maximum standardized uptake value (SUVmax) and metabolic tumor volume (MTV) of the primary tumor were measured by F-18 FDG PET/CT. MTV might be viewed as a collection of absolute SUV values equal to or greater than a certain threshold on each axial image of PET/CT. The ROC curve was used to determine the appropriate cut-off point of SUVmax and MTV. The prognostic significance of MTV, SUVmax was assessed in the study. Meanwhile, the paper studies the relation between SUVmax, MTV, and primary tumor volume (PTV). Receiver operating characteristic (ROC) analysis was used to determine the optimal MTV cut-off value.
Positive correlations between PTV and MTV, SUVmax and MTV were found. PTV, SUVmax, and MTV were significant predictors of survival. The 3-year progression-free survival (PFS) for SUVmax≤8.20 and SUVmax>8.20 were 91.1% and 73.0% (p = 0.027). With furthermore analysis, patients having tumor with lower MTV had higher 3-year PFS than patients having tumor with higher MTV. The percentage of the MTV5.0 in PTV was 14.66±15.75% (95%CI,11.20-18.13).
Our study indicated that PET/CT-derived parameters, SUVmax and MTV, are very important in assessing prognosis and making radiotherapy planning. Patients having tumor with lower MTV had higher 3-year PFS than patients having tumor with higher MTV. It is necessary to give a more aggressive treatment for patients with higher MTV. The MTV5.0 might be an appropriate quantitative definition of hypoxic sub-volumes for radiotherapy boost to improve the therapeutic effect.
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