ARE STILL FIDUCIAL MARKERS ALONE APPROPRIATE IN THE IMAGE GUIDED ERA FOR PROSTATE CANCER RADIOTHERAPY? A SINGLE INSTITUTION EXPERIENCE BASED ON A “WELL TRAINED” PATIENT SUBGROUP.

Simona Allis MD*, Riccardo Ragona PhD, Silvia Maria Anglesio PhD, Andrea Ricci MD,
Francesco Porpiglia MD, Marco Cossu MD, Alessia Reali MD, Gianluca Mortellaro and Maria Grazia Ruo Redda MD

ABSTRACT

Purpose: The purpose of this work is to assess the consistency of Fiducial Markers (FM) based IGRT in clinical practice and the magnitude of daily prostate gland displacements in a subgroup of patients carefully trained to maintain a constant and reproducible organ filling. Methods: A physician trained each patient in this selected 55 patients group, assuring a highly reproducible and well-administered self-preparation. Three FMs were implanted using a transrectal ultrasound technique. IGRT was achieved by daily single exposure MV portal images and, every 6 treatment sessions, double exposure portal images were acquired in order to evaluate differences in displacements between fiducial markers and bony structures. Results: There were no grade 3-4 complications (e.g. infections, bleeding or abscess) or significant patient reported discomfort related to FM insertion. Differences in displacements between FM and bony landmark resulted to be statistically significant (p<0,05), relating to a good self preparation. Displacement recorded during first five treatment sessions are not predictive of movement directions during remaining fractions. Conclusions: FMs give the opportunity, even in centers not equipped with in-room volumetric imaging systems, to perform IGRT. FMs-IGRT in combination to high quality patient rectal and bladder preparation allows an improvement of dose delivery and local control while reducing radiotherapy-related toxicity and overall treatment time. Images control has to be carried out every day in order to be clinically useful as displacements occur in random directions.

Keywords: 1. Prostate Cancer, 2. Radiotherapy, 3. Fiducial Markers, 4. Rectal filling, 5. Bladder Filling.