Quality assurance and uncertainty analysis in prostate conformal radiotherapy (in French)

Abstract

Conformal radiotherapy is a relatively new high‐precision treatment planning and delivery technique that requires much quality assurance, mostly during its implementation. Our study involved the eight centers participating in the French phase II dose escalation study with conformal radiotherapy for the cancer of the prostate. The dose escalation protocol consisted of five dose levels (66, 70, 74, 78, and 80 Gy ICRU prescription dose). The quality assurance topics examined are the following: (1) the target volume and organs at risk delineation uncertainty; (2) the planning target volume definition by means of 3D expansions; (3) the verification of the delivered dose under reference conditions and the dosimetric data used for treatment planning; (4) the development and comparison of different calculation methods for normal tissue complication probability; (5) a treatment planning and dose calculation intersite comparison; (6) a comparison and evaluation of the treatment planning data (volumes, doses, and dose–volume histograms) for the patient treatments included in the clinical study; and (7) the verification of the dose delivered to the prostate, determined by measurement of the entrance and exit doses and reconstruction of the dose in the prostate. The major intersite uncertainty of our study concerned the target volume delineation (σ>10% of the mean volume). The uncertainty due to the treatment planning and dose calculation procedure has been kept to significantly lower levels, owing to the use of a common treatment planning protocol describing the treatment modalities and the dose criteria for treatment plan evaluation.

The GETUG 70 Gy vs. 80 Gy randomized trial for localized prostate cancer: Feasibility and acute toxicity

“…Special attention was devoted to volume delineation, because it was the greatest factor of uncertainty in the escalation dose study (24). Analysis of the DVHs from the previous study permitted the definition of acceptable constraints.…”