Prognostic Role of Interim 18f-FDG-PET/CT during Chemoradiotherapy in Hypopharyngeal Carcinoma

Abstract

Our study aimed to investigate the prognostic values of interim 18fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (PET/CT) during definitive chemoradiotherapy (CRT) in patients with hypopharyngeal squamous cell carcinoma. The pretreatment and interim PET/CT images of 39 patients with hypopharyngeal squamous cell carcinoma, receiving definitive radiotherapy (RT) with platinum-based chemotherapy between February 2014 and May 2018, were evaluated prospectively. RT was delivered 5 days a week using a single daily fraction of 1.8 Gy, to a total dose of 70.2 Gy. The interim PET/CT images were taken at a cumulative RT dose ranging from 36.0 to 45.0 Gy. The maximum standardized uptake value (SUVm), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) of primary tumor (PT) and index node (IN) ［defined as a lymph node with highest TLG］ on both pretreatment PET/CT and interim PET/CT (iPET) were measured. The reduction ratio of the SUVm (SRR), MTV, and TLG between the two images was calculated. Progression-free survival (PFS) was calculated using the Kaplan-Meier method. The log-rank test and the Cox proportional hazards model were used for univariate and multivariate analyses, respectively. The median follow-up time was 24 months (range, 6-60 months). The 2-year PFS rate was 69.8 %. Twelve (30%) of 39 patients experienced disease recurrence (n=11, 28%) or death (n=4, 10%). In univariate analysis, a higher pretreatment MTV-PT (p=0.019), interim SUVm-PT (p=0.011), interim MTV-PT (p=0.034), iTLG-IN (p=0.012) and a lower SRR-PT (p=0.011) were associated with the inferior PFS. Conducting a multivariate analysis revealed that a higher interim SUVm-PT, interim TLG-IN and a lower SRR-PT were associated with the inferior PFS. The metabolic parameters of iPET can be useful predictors of patient outcome. An interim SUVm-PT, an interim TLG-IN, and a SRR were found to be the prognostic indicators of treatment outcome.