Head & neck squamous cell carcinoma: Comparison of multimodal imaging with pathological specimens

• Purpose: In head and neck cancer, tumor volume is a major concern and despite development in imaging modalities, precise target definition remains a challenge. In this study, tumor volumes defined from multimodal imaging with PET/MRI are compared with the actual pathological tumor volumes from the surgical specimens. The mismatch between the volumes defined from imaging and pathology is estimated and the clinical impact of potential mismatch is evaluated. Methods and Materials: Twenty-eight patients with head and neck squamous cell carcinoma, were scanned on an integrated PET/MRI system, prior to surgery. Three GTV’s were delineated defined from the MRI (GTVMRI), the PET (GTVPET) and one by utilizing both anatomical images and clinical information (GTVONCO). Thirty-three specimens were extracted en bloc and scanned with the same PET/MRI and were co-registered to the patient images based on predefined anatomical landmarks. Each specimen was sectioned in blocks, which were then sliced (4-µm thick) and stained with haematoxylin and eosin. All slices were digitalized, scanned and assessed by a trained head and neck pathologist. The pathological tumor areas for each tumor were interpolated yielding a pathological 3D tumor volume (GTVPATO), which was imported in Eclipse TPS (Varian Medical Systems, Palo Alto, CA) as a structure. The GTVPATO was compared with the GTV’s defined from imaging. Additionally, the mismatch between GTV’s were assessed by dividing the GTVPATO that is outside the imaging GTV with the whole volume of the corresponding GTV. To validate current practice of a 5 mm CTV expansion, a margin of 5 mm was added to the GTVONCO and the mismatch was re-assessed. Results: For consistency, only T-sites were included in this analysis (N=27). Further thirteen patients were excluded before the analysis, because fragmentation of the specimen during histologic processing or poor interpolation and insufficient number of points to form a structure in Eclipse. For the fourteen patients that were included in the analysis the mean volume of the GTVONCO was larger than the other GTV’s. In four patients the GTVPATO was larger than the GTVMRI and for one patient the GTVPATO was larger than the GTVPET. The mean mismatch of the GTVPATO when evaluated to the GTVPET, GTVMRI and GTVONCO was 29.7%, 39.5% and 7.5% respectively (Table 1). However, after the addition of 5mm margin all GTVPATO’s were encompassed in GTVONCO. Conclusions: GTV was defined differently with different imaging modalities and a mismatch with the pathological tumor volume was observed in thirteen of the fourteen included patients. For all patients, 5mm margin appears sufficient to ensure that all of the pathological information will be included during treatment.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Cancer och onkologi (hsv//swe)

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

Nyckelord

Squamous cell carcinoma

Head & Neck

PET/MRI

Target definition

Publikations- och innehållstyp

vet (ämneskategori)

kon (ämneskategori)