Dosimetric comparison of pre-planned and OR-planned prostate seed brachytherapy

Purpose: To compare the dosimetry of the traditional two step procedure (vo lume study + treatment planning several weeks later) with that of an OR-bas ed single procedure in which these two steps follow one another immediately , Computer generated treatment plans were used in both procedures. Methods and Materials: Several dosimetric parameters relating to target cov erage were obtained from dose volume histograms of CT-based evaluation plan s developed either 1 or 3 days following seed implantation. A total of 113 patients with early stage (T1C, T2A) prostate cancer were used for this ret rospective study. Results: The fraction of target (prostate) covered by the prescription dose (144 Gy), 90% of the prescription dose (115 Gy), and the dose encompassing 90% of the target in the evaluation plan were all statistically significan tly improved for OR-based plans compared to pre-planned cases. Conclusion: In our hands, there is a small but significant improvement in d ose coverage of the prostate when the ultrasound volume study and treatment planning are combined into a single procedure. (C) 2000 Elsevier Science I nc.