BACKGROUND: Recent evidence indicates that FDG-PET/CT-guided surveillance after concurrent chemoradiation (CCRT) in patients with locally advanced head and neck squamous cell carcinoma (LAHNSCC) comes with a slightly favorable hazard ratio for death, results in considerably fewer operations and is more cost-effective as compared with neck dissection (Mehanna H, et al. NEJM 2016). FDG-PET/CT is highly accurate in detecting residual and/or recurrent HNSCC and greater specificity is obtained for that purpose when scans are performed 12 or more weeks after CCRT (Cheung PKF, et al. Otolaryngol Head Neck Surg. 2016). With respect to p16 expression, the HPV status of LAHNSCC of the oropharynx is a strong and independent prognostic factor for survival (Ang KK et al. NEJM 2010).
METHODOLOGY: A total of 152 newly diagnosed LAHNSCC (stage IVa/b) patients undergoing CCRT were recruited for participation to a prospective multicenter trial. Study design included FDG-PET/CT twelve weeks after end of CCRT, assessment of the time to nodal recurrence, local recurrence rate, recurrence-free survival (both locoregional and distant) and overall survival (OS), and, determination of HPV status using p16.
RESULTS: Eighty two percent of included patients (125 out of 152) had adequate primary tumor control after CCRT. During a median follow-up of 20.4 months, neck recurrence occurred in 18% of these patients (23 out of 125) resulting in an overall neck dissection rate of 16% combined with a 86% 2-year OS. In patients with negative 12 week FDG-PET/CT, OS was comparable irrespective of neck dissection (p=0.4).
The diagnostic test characteristics (with 95% CI) of FDG-PET/CT 12 weeks after end of CCRT to detect residual locoregional disease and predict locoregional or distant recurrence during 12 months follow-up are shown below.
||Negative Predictive Value (NPV)
||Positive Predictive Value (PPV)
|Residual disease or locoregional or distant recurrence
Among the participants with oropharyngeal cancer in follow-up (55%; 69 out of 125 patients) both OS and recurrence-free survival were significantly longer with a positive HPV status (p-value 0.017 and 0.019, respectively). For the whole study population both visual PET-CT analysis and p16+ status were prognostic for OS and time to nodal recurrence (p<0.0001).
CONCLUSIONS: The results of this prospective multicenter trial clearly illustrate the high diagnostic and predictive test characteristics of FDG-PET/CT twelve weeks after end of CCRT in patients with LAHNSCC, specifically regarding the prediction of nodal recurrence. The strategy results in a low overall neck dissection rate of 16% in combination with a high 2-year OS rate of 86%. In addition, the results confirm HPV status as a strong predictor of OS in the subgroup with oropharyngeal LAHNSCC.