Image validation of laryngeal and hypopharyngeal cancer with histopathology for radiotherapy.

Irradiation of the larynx and the hypopharynx using modern fractionation
schedules leads to favourable cure rates at the expense of a relatively large
number of severe (15%) and mild complications (40%). Currently, radiation
treatment of the larynx consists of high dose irradiation of the complete
larynx without delineation of the tumour volume. This is caused by the lack of
information on the extent of the tumour. The hypothesis of the study is that
the tumour volume can be determined by a combination of MRI, DCE-CT and FDG-PET
and that smaller target volumes will be delineated if a combination of these
image modalities is used. Reduction of the target volume for radiation therapy
will reduce the number and decrease the severity of complications.

The accuracy of the different imaging modalities will be assessed with
histopathology as the reference. Further, histopathology will be used to
estimate the microscopic extension of the tumour in the surrounding tissue. The
topological correspondence is defined as the conformity index: 2*
volume_overlap_region/(volume_regio1 + volume_regio2)

This study is a descriptive, diagnostic study, that will evaluate DCE-CT,
FDG-PET and MRI for tumour delineation in laryngeal and hypopharyngeal cancer.
To account for interobserver variations, the tumour volume will be delineated
independently by two observers in all the image modalities. The overlap between
the delineated GTVs of both observers as calculated for the different image
modalities will be presented as a conformity index. Further, the interobserver
overlap will also be described as a conformity index.

Apart from the normal clinical imaging procedure, all patients will undergo a
DCE-CT with a higher dose than the normal multi slice CT. Moreover, all imaging
procedures will be performed in a mask before the total laryngectomy, which may
be burdensome for the patient. This enables the use of the presurgery images to
define the target volume in the routinely performed postsurgery radiotherapy,
that might improve target volume definition and minimize radiation dose to
normal structures. In the days before surgery, patients are hospitalized and,
therefore, generally no extra visits to the hospital will be required. Because
of the extensive histopathological procedure, the pathological diagnosis will
be available several days later than normally. This will not delay the adjuvant
radiotherapy treatment of the patient.