3517 - 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).

Background

The role of FDG-PET/CT in the FU of LA-HNSCC is unclear.

Methods

Scan 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.

Results

We 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).

Conclusions

FU-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.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.