Treatment planning techniques in pelvic irradiated patients
Comparison between 3D conformal and IMRT treatment planning techniques in supine and prone position in patients who receive pelvic irradiation

The aim of this study is to determine if in patients who are referred for
pelvic irradiation, IMRT planning in comparison with 3-D conformal radiotherapy
planning, gives the lowest dose to the small bowel without increasing the dose
in other organs at risk (bladder, kidneys, rectum and sigmoid). In addition, we
want to determine in which patients (postoperative endometrial and/or cervical
and/or rectal cancer patients), according to dose volume histograms,
irradiation in prone position is superior to supine position. For this, we need
to perform two consecutive CT-scans in prone and supine position respectively,
and delineate on both scans the target organs as well as the organs at risk.
Finally, we need to make four treatment plans for every patient, one IMRT plan
in supine position, one IMRT plan in prone position, one 3D conformal plan in
supine position and one 3D conformal plan in prone position and compare these
plans with each other.

Primary objectives:
To compare the dose volume histograms (DVHs) of the planning target
volume (PTV) in prone and supine position, with 3D conformal and
intensity-modulated radiotherapy (IMRT) planning in patients who receive pelvic
irradiation
To compare the dose volume histograms (DVHs) in the organs at risk in
prone and supine position, with 3D conformal and intensity-modulated
radiotherapy (IMRT) planning in patients who receive pelvic irradiation



Secondary objectives:
To determine if and for which patients (postoperative endometrial
and/or cervical and/or rectal cancer patients) IMRT is superior to 3D conformal
planning
To determine if and for which patients prone position is superior to
supine position

Patients, referred to our department for curative treatment of their
gynaecological or rectum tumor, will be asked informed consent.
1 extra ctscan in supine position will be made in preparation for radiotherapy
treatment. The target volume and critical organs will be delineated by the
investigator on the routinely made ctscan and the additional ctscan . Radiation
technologists will make 4 treatment plannings using 3-D conformal radiotherapy
and IMRT in supine and prone position.

No intervention

The extent of the burden for this patient group participating the study is very
minimal. The additional ctscan takes only 5-10 minutes more and will give a
dose of 4 Milliesievert. The risk of tumor induction is very low especially in
comparison with the radiation dose the patient will receive. For the study
patients there will be no benefit.
The IMRT planning might be benefitial with relation to the critical organs,
especially the small bowels. Acute and long term toxicity will be less.
This will be benefitial for all patients that will be irradiated for a pelvic
tumor.