Comparison of subjective evaluation versus objective algorithm in the interpretation of follow-up FDG-PET/CT scans after radiochemotherapy in head and neck cancer patients

Abstract

Aim Retrospective evaluation of serial FDG-PET/CT scans in head and neck squamous cell cancer (HNSCC) patient’s follow-up after primary radiochemotherapy (RCTx), to assess the diagnostic accuracy of an experienced observer vs. an objective classification compared to standard clinical follow-up examinations.

Methods Sixty-nine patients with locally advanced HNSCC were included, who received curative RCTx. Follow-up included serial FDG-PET/CT at the following time intervals t1: ≤ 270 d, t2: 271–540 d, t3: > 540 d after curative RCTx. The likelihood to detect local recurrences, nodal and distant metastases were compared between (i) experienced observer, (ii) an objective classification system by Zundel et al. [25], and (iii) routine clinical follow-up examinations.

Results Twenty-two local recurrences, 7 nodal and 17 distant metastases were recorded during the follow-up. The diagnostic accuracy for local recurrence of the experienced observer vs. objective classification was 78 % vs. 77 % for t1, 83 % vs. 79 % for t2 and 100 % vs. 84 % for t3.

The classification (ii) and the conventional follow-up (iii) resulted in a relatively high amount of equivocal findings reducing the diagnostic accuracy.

Conclusion Evaluation of FDG-PET/CT by an experienced observer in follow-up of HNSCC patients after curative RCTx resulted in the highest diagnostic accuracy in comparison to an objective classification and to routine clinical examination.

HNSCC is a malignant tumor with a high likelihood of recurrence, especially in the first two years after curative RCTx. Early detection of recurrence is of high clinical importance, since there are several effective second line therapies that may have curative potential in some patients.

Zusammenfassung

Ziel Retrospektive Analyse der FDG-PET/CT in der Nachsorge von Patienten mit primär radiochemotherapierten zervikalen Plattenepithelkarzinomen (HNSCC). Vergleich der diagnostischen Genauigkeit des erfahrenen Befunders mit einem objektiven Klassifizierungssystem und mit der klinischen Nachsorgeuntersuchung.

Methoden 69 Patienten, die wegen eines lokal fortgeschrittenen HNSCC eine kurative Radiochemotherapie (RCTx) erhielten, wurden eingeschlossen. Die Nachsorge umfasste serielle FDG-PET/CT nach RCTx zu folgenden Zeitintervallen t1: ≤ 270 d, t2: 271–540 d, t3: > 540 d. Die Detektionsraten von Lokalrezidiven, Lymphknoten- und Fernmetastasen durch den erfahrenen Befunder (i), das objektive Klassifikationsverfahren (ii) nach Zundel [25] sowie durch die routinemäßige klinische Nachsorge (iii) wurden verglichen.

Ergebnisse Insgesamt wurden 22 Patienten mit Lokalrezidiven, 7 mit Lymphknoten-, und 17 mit Fernmetastasen detektiert. Die diagnostischen Genauigkeiten des erfahrenen Untersuchers (i) und des objektiven Klassifizierungssystems (ii) bezüglich der Lokalrezidive betrugen 78 % und 77 % zu t1, 83 % bzw. 79 % zu t2 und 100 % bzw. 84 % zu t3. Das Klassifizierungssystem nach Zundel, aber auch die konventionelle Nachsorgeuntersuchung führte zu einem relativ hohen Anteil uneindeutiger Befunde, was sich negativ auf die diagnostische Genauigkeit auswirkte.

Schlussfolgerung Die Auswertung der FDG-PET/CT bei Patienten mit lokal fortgeschrittenen HNSCC nach kurativer RCTx durch den erfahrenen Befunder hat die höchste diagnostische Genauigkeit für die Detektion von Lokalrezidiven und/oder Metastasen im Vergleich zu einem objektiven Klassifizierungssystem und der routinemäßigen klinischen Nachsorge.

Vor dem Hintergrund zahlreicher effektiver Zweitlinientherapien mit teils kurativem Potenzial und der hohen Rezidivneigung in den ersten beiden Jahren nach Primärtherapie ist die frühzeitige und exakte Detektion von Rezidiven und Metastasen bei HNSCC-Patienten von großer Bedeutung.

Key words

HNSCC - radiochemotherapy - FDG-PET/CT - subjective observer - objective algorithm - follow-up

Schlüsselwörter

HNSCC - Radiochemotherapie - FDG-PET/CT - subjektiver Untersucher - objektiver Algorithmus - Nachsorge

^* These authors share the senior authorship.

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