Fluorodeoxyglucose (FDG)-PET/CT surveillance using a standardized reporting criteria 12 weeks after concurrent chemoradiotherapy (CCRT) was reliable in patients with locoregionally advanced head and neck squamous cell carcinoma (HNSCC), except in patients with late manifesting residual disease, according to the results of the ECLYPS study, published in the Journal of Clinical Oncology.
The study assessed FDG-PET/CT using Hopkins reporting criteria for evaluating response. These criteria compare residual FDG uptake vs anatomic reference sites to differentiate malignant from benign lesions.
A prior study demonstrated that the use of FDG-PET/CT scanning as a surveillance tool showed noninferior overall survival and was cost-effective compared with routine neck dissection; however, a lack of standardized reporting criteria in the study has hampered translation into clinical practice.
“ECLYPS confirmed that FDG-PET/CT can rule out residual neck disease 12 weeks after CCRT, but its sensitivity was found to be strongly time dependent,” wrote Tim Van den Wyngaert, MD, PhD, of the department of nuclear medicine at Antwerp University Hospital in Belgium, and colleagues. “That is, PET/CT can identify residual disease in patients who relapse up to a 9-month horizon after imaging with high sensitivity, but it is less able to do so for patients in whom residual disease was detected up to 12 months after imaging (sensitivity, 59.7%).”
This result may explain some of the heterogeneity found in prior studies of FDG-PET/CT surveillance given variable follow-up times.
This study included 125 patients with newly diagnosed locoregionally advanced HNSCC who underwent FDG-PET/CT surveillance 12 weeks after completing CCRT. The primary outcome was the negative predictive value of FDG-PET/CT scans.
After a median follow-up of 20.4 months, 18.4% of patients had residual neck disease.
There were 9 false-positive scans, and all had a Hopkins score of 4. There were 8 false-negative scans, with one having a Hopkins score of 3 and the other 7 with a score of 1. This yielded a negative predictive value of 92.1%.
The researchers found no statistically significant difference in the diagnostic performance using Hopkins criteria compared with local nonstandardized assessment. However, they noted that “the number of scans with scores reflecting diagnostic uncertainty was significantly lower with the use of the Hopkins criteria.”
A time-dependent analysis showed a decrease in sensitivity according to the time horizon of clinical follow-up. The sensitivity decreased from 83.3% at 3 months to 59.7% at 12 months.
“The sensitivity to identify patients with residual neck disease manifesting beyond 9 months after imaging is low, and this was not resolved by using standardized reporting criteria,” the researchers wrote. “An additional PET/CT surveillance scan 1 year after the end of CCRT may be warranted, especially in HPV-negative patients.”