Tumor volume definitions in head and neck squamous cell carcinoma - Comparing PET/MRI and histopathology

• Background and purpose: In cancer treatment precise definition of the tumor volume is essential, but despite development in imaging modalities, this remains a challenge. Here, pathological tumor volumes from the surgical specimens were obtained and compared to tumor volumes defined from modern PET/ MRI hybrid imaging. The purpose is to evaluate mismatch between the volumes defined from imaging and pathology was estimated and potential clinical impact.Methods and Materials: Twenty-five patients with head and neck squamous cell carcinoma were scanned on an integrated PET/MRI system prior to surgery. Three gross tumor volumes (GTVs) from the primary tumor site were delineated defined from MRI (GTVMRI), PET (GTVPET) and one by utilizing both anatomical images and clinical information (GTVONCO). Twenty-five primary tumor specimens were extracted en bloc, scanned with PET/MRI and co-registered to the patient images. Each specimen was sectioned in blocks, sliced and stained with haematoxylin and eosin. All slices were digitalized and tumor delineated by a head and neck pathologist. The pathological tumor areas in all slices were interpolated yielding a pathological 3D tumor volume (GTVPATO). GTVPATO was compared with the imaging GTV's and potential mismatch was estimated.Results: Thirteen patients were included. The mean volume of GTVONCO was larger than the GTV's defined from PET or MRI. The mean mismatch of the GTVPATO compared to the GTVPET, GTVMRI and GTVONCO was 31.9 %, 54.5 % and 27.9 % respectively, and the entire GTVPATO was only fully encompassed in GTVONCO in 1 of 13 patients. However, after the addition of a clinical 5 mm margin the GTVPATO was fully encompassed in GTVONCO in 11 out of 13 patients.Conclusions: Despite modern hybrid imaging modalities, a mismatch between imaging and pathological defined tumor volumes was observed in all patients. A 5 mm clinical margin was sufficient to ensure inclusion of the entire pathological volume in 11 out of 13 patients.(c) 2023 The Authors. Published by Elsevier B.V. Radiotherapy and Oncology 180 (2023) 1-8 This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine (hsv//eng)

Nyckelord

Squamous cell carcinoma of head and neck

Magnetic resonance imaging

Positron emission tomography

Pathology

modulated radiation-therapy

interobserver variability

oral-cavity

fdg-pet

delineation

laryngeal

hypopharyngeal

ct

oropharyngeal

margin

Oncology

Radiology

Nuclear Medicine & Medical Imaging

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