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Technical and clinical evaluation of image guided conformal arc radiotherapy for localized prostate cancer

Tuesday, 29 May, 2007 - 17:00
Campus: Brussels Health Campus
Faculty: Medicine and Pharmacy
auditorium P. Brouwer
Guy Soete
phd defence

The purpose of radiotherapy is to sterilize
malignant tumours and at the same time to avoid
radiation injury to the surrounding healthy
tissues. Two recent technical developments have
dramatically increased the precision of
radiotherapy: conformal and image guided
radiotherapy. The former aims at shaping the
dose distribution to the shape of the target. The
latter aims at delivering this conformal dose to a
precise location within the patient.

The thesis summarizes the evaluation and clinical
implementation of image guided conformal arc
therapy for prostate cancer. The positioning
system uses automatic co-registration of X-ray
images with a reference image set from the
planning CT. Phantom measurements showed an
accuracy at the mm level. Applied to patients,
setup errors were reduced by X-ray compared to
conventional positioning using skin drawings and
lasers, leading to a reduction of normal tissue
irradiation. Setup errors were further reduced by
use of implanted radio-opaque markers. In a
subsequent study, conformal arc therapy was
compared to intensity modulated radiotherapy.
Both techniques were equivalent in case of a
convex target shape. Because of its superior
treatment efficiency, conformal arc therapy is
considered the treatment of choice for a convex
target. The last study documented favourable
patient outcome after clinical implementation of
X-ray positioning and conformal arc therapy.

Our results contribute to the debate whether
patients with localized prostate cancer should be
submitted to the hazards of radical
prostatectomy. With modern radiotherapy
techniques, a randomized trial comparing both
treatment modalities seems no longer unethical.