PET zur Responsebeurteilung nach Strahlentherapie: Stand der Dinge

Zusammenfassung

Die Responsebeurteilung nach Strahlentherapie ist mit Schwierigkeiten behaftet. Die Bestrahlung initiiert eine Gewebereaktion, in der gleichzeitig mit der Apoptose im Tumor eine zum Teil granulozytäre, inflammatorische Reaktion des gesunden Gewebes auftritt. Zusätzlich begünstigt das gehäufte Auftreten von Makrophagen eine Akkumulation von 18F-FDG, die nach der Behandlung das Vorhandensein von Tumor imitiert und daher gehäuft falsch positive Ergebnisse liefert und in diesem Zusammenhang die Frage nach dem optimalen Evaluationszeitpunkt aufwirft. Noch schwieriger ist die Responsebeurteilung zu einem frühen Zeitpunkt während der Therapie, beispielsweise in einem neoadjuvanten Konzept. Hier sind vor allem beim Rektumkarzinom mittlerweile Studiendaten vorhanden, die eine gute Korrelation von PET-Scans nach neoadjuvanter Radiochemotherapie mit der histopathologischen Remission zeigen, während PET in anderen Lokalisationen nicht mit gleich guten Ergebnissen eingesetzt wurde.

Abstract

Response-Evaluation following radiotherapy is associated with difficulties mainly based on inflammatory tissue reactions comprising apoptosis within the tumour and granulocytic aggregation around the tumour. The increased number of macrophages causes an increased 18F-FDG uptake which mimicks malignant uptake and generates false- positive results which in this context arises the question of the optimal evaluation time point after radiotherapy.

Even more difficult remains response evaluation at an earlier time point during radiotherapy, e. g. in neoadjuvant treatment regimes. Especially in rectal cancer, study data show that PET scans show good correlation with histopathologic response after neoadjuvant chemoradiotherapy while PET has not been used with equal advantage in other locations.

Schlüsselwörter

Response - neoadjuvant - Radiochemotherapie - Zeitpunkt

Key words

response - neoadjuvant - radiochemotherapy - time-point

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