Pathological Validation of Functional Imaging in Head and Neck Squamous Cell Carcinoma. A Prospective, Non-commercial and Mono-centric Study
1. BACKGROUND AND SETTING
Concurrent (chemo-) radiotherapy (CRT) is the current standard of care for patients
with locally advanced head and neck squamous cell carcinoma (HNSCC). The proximity of
important functional structures with the tumour makes treatment however highly complex.
Treatment related toxicity can be severe with xerostomia and dysphagia gravely
complicating the patient's quality of life. The use of altered fractionation schedules
and/or concurrent chemotherapy has resulted in substantial gains in loco-regional
control, leading to significant improvements in overall survival. Although the
prognosis of patients treated with RT for locally advanced HNSCC is continually
improving, there are still a high number of locoregional failures.
Using highly conformal radiotherapy the investigators can increase the therapeutic
index by giving higher doses to the more radio-resistant parts of the tumour while
maintaining or even reducing dose to the surrounding tissues. Functional imaging can
help us to define these radio-resistant subvolumes and help us to delineate the gross
tumour volume (GTV) better in the future. Positron emission tomography (PET), Diffusion
weighted magnetic resonance imaging (DWI) and Dynamic contrast enhanced MRI (DCE-MRI)
can give us further insight in the tumour's underlaying biological and microstructural
characteristics. However, at the moment the investigators are not sure how to interpret
the different imaging parameters obtained from these functional imaging modalities.
Therefore, the investigators want to correlate the imaging parameters with the
pathological characteristics of the tumour. On the other hand the investigators want
to correlate the GTV defined on the functional imaging modalities with the pathological
GTV, and see if these modalities can help us to delineate the GTV more accurately in
1.2. IMAGING MODALITIES
1.2.1. FDG-Positron Emission Tomography (FDG-PET)
Increased glucose metabolism is a fundamental characteristic of many malignant tumours,
including HNSCC. Positron emission tomography (PET) after injection of radioactively
labeled 2' fluorodeoxyglucose (18F-FDG) can help us measure and quantify this
metabolism in tumours, using the standardized uptake value (SUV). Several studies have
correlated high SUV prior to treatment with significantly worse outcome in HNSCC.
Furthermore it appears that most local recurrences occur within the FDG-PET defined
GTV. The molecular base for this is not completely understood.
Proliferating tumour cells consume glucose at a high rate and release lactate and not
CO2. This way they omit the mitochondria driven oxidative phosphorylation of glucose
from the production of ATP (=Warburg-effect). Several molecular parameters have been
associated with this glycolytic switch, such as activation of the hypoxia induced HIF1α
and the increased presence of GLUT glucose transport proteins. So far no clear
correlation was found between the presence of hypoxia and FDG-uptake.
1.2.2. Diffusion-weighted Magnetic resonance imaging (DWI)
Diffusion weighted magnetic resonance imaging (DWI) can characterize tissues based on
the random displacement of water molecules. In biological tissues this displacement is
limited by underlying tissue-specific barriers and this difference can be quantified
and visualized using apparent diffusion coefficient (ADC) values. A study on 165
patients in our centre with HNSCC demonstrated that the pre-treatment ADC value is a
strong and independent prognostic factor for outcome. Patients with a high ADC value
respond worse to ionizing radiation than patients with a lower ADC value. There is
currently no clear explanation why tumours with a higher cellular density are more
radiosensitive than tumours with a low density. A number of microscopic features effect
water diffusivity in tissue (presence of necrosis, cellular density, inflammation,
integrity of cellular membranes). Many of these also affect the radio- and
chemosensitivity of the tumours.
1.2.3. Dynamic contrast enhanced Magnetic resonance imaging (DCE-MRI)
Dynamic contrast enhanced MRI (DCE-MRI) is a non-invasive imaging modality which has
been developed and evaluated for the characterization of vascular properties of
tissues. Adequate oxygen supply is essential for the effectivity if ionizing
radiation. However tumor angiogenesis is far from perfect and newly formed vessels
display permeability, tortuosity and a generally poor functionality. These vascular
properties could provide us insight in the aggressiveness and radiosensitivity of the
tumor. Dynamic computed tomography (CT) has demonstrated that perfusion measurements
can predict outcome in head and neck cancer after radiotherapy. Similarly quantitative
assessment of DCE-MRI has also been correlated with response to ionizing radiation in
patients with HNSCC. A recent trial on a limited number of patients correlated certain
DCE-MRI parameters with intratumoural hypoxia. However, so far no spatial correlation
has been done.
2. STUDY OBJECTIVES
2.1. PRIMARY OBJECTIVES
The main objective of this study is to correlate DWI, DCE-MRI and FDG-PET with the
spatial distribution of hypoxia in patients with head and neck cancer.
2.2. SECONDARY OBJECTIVES
A. To correlate findings on functional imaging with intrinsic molecular parameters
depicting proliferation, hypoxia and glucose metabolism.
B. To validate the use of the hypoxia markers and the 15-gene hypoxia gene expression
C. To compare tumour volume as derived from pathology with the volumes delineated on
the several anatomical and functional imaging modalities.
3. STUDY DESIGN
The target group for this trial is patients with a histologically proven squamous cell
carcinoma of the larynx, eligible for surgery, staged T3-4. Prior to treatment patients
will undergo an FDG-PET/CT and MRI with DW and DCE, dedicated for optimal visualization
of the primary tumor and analysis. The imaging modalities will be performed as close
to the surgery as possible (PET/CT one week before surgery; MRI one day before
Prior to treatment, three slices on the imaging modalities will be selected by a
radiologist based on their visual quality and heterogeneity of functional parameters.
These regions of interest will be compared to different histopathological parameters on
the resection specimen. The radiologist will also select regions, based on DWI and DCE
parameters, who are suspect to be hypoxic. From these regions a biopsy will be taken.
After total laryngectomy, the resection specimen will be oriented, and biopsy material
will be obtained from the regions in the tumour that have been selected on the imaging
modalities The rest of the specimen will be fixed in formaldehyde. To account for the
shrinkage of the tumour due to fixation, the resection specimen will be placed in a
cardboard box with an agarose solution and scanned with an MRI with T1w/T2 images. From
this a shrinkage factor will be calculated comparing the delineated T1 and T2 weighted
After fixation the tumour will be cut up into macroslices with a thickness of about
5mm. On each macroslice tumour volume will be delineated. Using this, the pathological
tumour volume will be determined taking into account the previously determined
shrinkage factor. This pathological volume will be compared to the tumour volume
delineated on the imaging modalities. On the different pre-surgery functional imaging
modalities, 4 separate observers will delineate the GTV. The different volumes will be
compared and overlap will be calculated after 3D specimen reconstruction and
The GTV obtained from the functional imaging will be correlated with the pathological
tumor volume of the resection specimen. This information will give us more insight into
the true power of the investigated functional imaging techniques in determining tumour
volume. This is important to assess the role of functional imaging modalities in
treatment planning in the future.
At the three levels, chosen by the radiologist on the imaging modalities, 4µm thick
slices will be taken. On each level an immunohistochemical staining will be carried out
(GLUT-1, CA-IX, HIF-1α, VEGF and KI 67 staining will be performed ).
IHC will be scored according to a semiquantitative scoring system using a field
analysis where each field will be assigend a score of 1-4 according to the approximate
area of immunostaining (0:0%, 1:1-5%, 2: 5-15%, 3: 15-30% and 4: >30%.
4. SAMPLE SIZE Twenty patients with squamous cell carcinoma of the larynx, planned to
undergo total laryngectomy, will be included.
Intervention Model: Single Group Assignment, Masking: Open Label
Correlation of functional imaging with tumor hypoxia.
The correlation of DWI, DCE-MRI and FDG-PET with the spatial distribution of hypoxia in patients with head and neck cancer.
2 years after start of the study.
Sandra Nuyts, PhD MD
University Hospitals Leuven
Belgium: Federal Agency for Medicines and Health Products, FAMHP