Real-life value of follow-up FDG-PET/CT (FU-FDG-PET/CT) in patients with locoregionally advanced squamous cell carcinoma of the head and neck (LA-HNSCC) treated with chemoradiation (CRT) or (chemo)radiation ([C]RT) preceded by induction chemotherapy (IC) (sequential treatment [ST]).

Purpose

To explore the clinical impact of FU-FDG-PET/CT in patients with LA-HNSCC treated with CRT or ST.

Methods

Real-life 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 histological proof of recurrence before FU-FDG-PET/CT. The reference standard was the occurrence of a second primary (SP) or a recurrence within 12 months after FU-FDG-PET/CT. Primary endpoints included sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) on a patient level.

Results

Between 7/10/2005 and 28/10/2016, 73 patients were identified: median age 61 (range 35-80), male: n=55. Primary tumor site: oropharynx: n=35; larynx: n=17; 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; NO: n=10; N1: n=7; N2: n=53; N3: n=3. Patients were treated by CRT (n=29), IC + CRT (n=43), IC + RT (n=1). Median time between end of treatment and FU-FDG-PET/CT was 12 months (range 6-17). Median follow-up 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, SPs and distant metastases were detected in 5, 1, 4 patients, respectively. 18 patients (25%) recurred after a false positive (n=8), false negative (n=2) or true negative (n=53) FU-FDG-PET-CT. One FU-FDG-PET/CT-detected local recurrence and one SP were treated with curative intent. All false-positive patients underwent biopsy (n=5) or surgery (n=3). Metastases were irradiated stereotactically in 2 patients. Median overall survival was 49 (95% CI 29 – 68) and 98 (95% CI 86-111) months in FU-FDG-PET/CT-positive and -negative patients, respectively (p = 0,000196).

Conclusion

FU-FDG-PET/CT in real-life has a high NPV, but low PPV. Prognostic value is significant but false-positive FU-FDG-PET/CTs induce invasive procedures in a significant fraction of patients.