1153P - Role of follow-up (FU) FDG-PET/CT (FU-FDG-PET/CT) in patients with locoregionally advanced squamous cell carcinoma of the head and neck (LA-HNSCC) treated with chemotherapy and radiotherapy (RT), either concurrent (CRT) or sequential (ST)

Abstract

BackgroundThe role of FDG-PET/CT in the FU of LA-HNSCC is unclear. MethodsScan reports of LA-HNSCC patients, having FU-FDG-PET/CT performed 6-18 months after ST/CRT were retrospectively analyzed. Equivocal reports were scored as positive. Excluded were patients with proven recurrence before FU-FDG-PET/CT. The reference standard was the occurrence of a second primary (SP) or a recurrence < 12 months after FU-FDG-PET/CT. Primary endpoints included sensitivity, specificity, positive (PPV) and negative predictive value (NPV) on a patient level. ResultsWe identified 73 patients. Primary tumor site: oropharynx: n=35; 7 larynx: n=7; hypopharynx: n=11; oral cavity: n=4; paranasal sinus: n=4; unknown: n=5. Tumor stage (UICC 7): II (T2N0): n=1; III: n=9; IV: n=63. T1: n=8; T2: n=20; T3: n=16; T4: n=24. N0: n=10; N1: n=7; N2: n=53; N3: n=2. Patients were treated by CRT (n=29) or ST (n=44). A prior FDG-PET/CT at 3 months after end of treatment (EOT) (EOT-FDG-PET/CT) had been performed in 69/73 (60 negative, 6 false and 3 true positive [resected lymph nodes]). FU-FDG-PET/CT in patients without EOT-FDG-PET/CT was true negative in 3 patients and true positive in 1. Median time between EOT and FU-FDG-PET/CT was 12 months (range 6-17). Median FU after FU-FDG-PET/CT was 48 months (range 2-130). Sensitivity, specificity, PPV and NPV were 83% (95% CI 52-98), 87% (95% CI 76-94), 56% (95% CI 31-78) and 96% (95% CI 87-100), respectively. Local recurrences, SP and distant metastases were detected in 5, 1, and 4 patients, respectively. One FU-FDG-PET/CT-detected local recurrence and 1 SP were treated with curative intent. All false-positive patients (n=8) underwent biopsy (n=3) or surgery (n=5). 15 patients (21%) recurred > 12 months after FU-FDG-PET-CT. Median overall survival was 49 (95% CI 29 - 68) and 98 months (95% CI 86-111) in FU-FDG-PET/CT-positive and -negative patients, respectively (p=0.000196). ConclusionsFU-FDG-PET/CT in real-life has a high NPV and significant prognostic value. However, false-positive scans induce invasive procedures in a significant fraction of patients. Legal entity responsible for the studyThe authors. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.