Study for optimizing the moment of "Adaptive radiotherapy" during curative radiotherapy or radiochemotherapy in Head and Neck cancer

During the 6-7 weeks of irradiation the tumor and surrounding organs at risk
change in shape and volume. Recent studies show that when the treatment was
adapted to these changes by using "Adaptive Radiotherapy", the therapeutic
ratio increased, particularly for the parotid glands. With this technique a new
plan is made at the end of the second week of the irradiation. Repeat scan in
the second week is based on a study by Van Kranen and published data which
showed a 10% decrease of the parotid glands volume. Unknown is if the second
week is the optimal timepoint for replanning. We like to investigate if the
second week is the right timepoint for replanning versus the third and fourth
week. Furthermore we like to analyse if the optimal moment of replanning is
depending on the location of the tumor, tumor volume or the absolute dose in
the organs at risk.

To investigate the optimal timepoint of replanning during a curative
radio(chemo)therapy in patients with Head and Neck cancer. Furthermore we like
to analyze if the optimal timepoint of replanning is depending on
tumorlocation, tumor volume or absolute dose in OaR.

Prospective study with 50 patients

Twice an extra CT scan without contrast

Twice an extra CT scan without contrast will be done; it will take an extra 30
minutes but there's hardly any risk and no extra hospital visits.
Radiation exposure per scan is 10mSv and negligible compared to the
radiotherapy treatment