In some cases, distant metastases may develop soon after completion of (C)RT although not detected during initial diagnostic workup. For clinical decision making, diagnosing distant spread of the disease at this phase is critical because radical surgery for loco-regional residual disease will probably not be considered beneficial in these cases.
FDG-PET/CT imaging is recognized as a preferred method for the detection of distant metastases in HNSCC,13,15,16 which further supports its use also in monitoring treatment response after (C) RT. In the present series, three patients (3%) were found to have distant metastasis in the post-treatment FDG-PET/CT, and one patient was found to have pulmonary metastases of a previous cancer.
The current study is limited mainly by the size of the patient series and by the retrospective nature of the analysis. It must be noted, however, that in the two meta-analyses cited earlier, there are only a few studies with a larger patient cohort. The present heterogeneity in the treatment modalities and in the patient characteristics reflect the typical clinical practice in the management of head and neck cancer.
The aim of the present study was to retrospectively audit our current protocol, and we did not address the question about the best available imaging modality in the post-treatment setting. To further clarify this issue, new prospective, comparative studies will be needed including also financial aspects.
In conclusion, the diagnostic accuracy of FDG-PET/CT in the assessment of treatment response after definitive (C)RT for HNSCC was good, further supporting its use in this setting. The NPV, specificity, and accuracy were high for both primary site and neck.
Also the PPV for the neck was high: there were no false positive findings in the assessment of neck nodes. Post-treatment FDG-PET/CT obviously has potential to guide clinical decision-making. Patients with negative scan can fairly safely be followed up clinically only, while positive scan necessitates a neck dissection and/or biopsies from the primary tumor area to rule out or confirm residual tumor.
HK was involved in the study design, collection and statistical analysis of data, and drafting of the manuscript. TM, JS, and KS were involved in the study design, collection of data, and drafting of the manuscript. AM was involved in the study design and in drafting and revisions of the manuscript. All authors read and approved the final manuscript.
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