Poster Presentation – Abstracts Archive

UK & Ireland Prostate Brachytherapy Conference 2017

Abstract number 19

A new technique on 4D real time interactive permanent prostate seed implant brachytherapy

Villalon Arias C*; Medford B*; Bourke E*; Rees G*; Hodgkinson S*; Lees K*
*Maidstone Hospital/Kent Oncology Centre

AIMS/INTRODUCTION: Kent Oncology Centre adopted in 2015 a new system for delivering Low Dose Rate Brachytherapy. This is a 4D prostate seed implant technique from the company BXT Accelyon.

MATERIALS/METHODS: 153 consecutive patients with carcinoma of the prostate were included in the study spanning 21 months. They were treated with an Iodine-125 permanent implant monotherapy giving a total dose of 145 Gy. 5 patients were excluded mainly because they had different treatment schemes. This new technique requires the data of a volume study of the prostate done between 3 – 4 weeks before treatment. The output in form of a nomogram gives us the needed number of radioactive sources along with their location. The day of treatment, the sources are implanted by means of several pre-waxed needles using transrectal ultrasound (TRUS) image guidance. 4 weeks later we perform a follow up CT (FU-CT) scan of the prostate.

RESULTS: The predicted volume of the prostate is on average 14.3(0.2)% smaller than that on the treatment day, partly because patients undergo hormone therapy. Despite this, the number of implanted sources is on average -0.6(0.1)% respect to the nomogram. Although some edema is produced due to needle insertion the FU-CT shows an average volume change of the prostate of only -0.1(0.1)%. Nonetheless some changes have been seen on the dosimetric quantities. Prostate V150 is the only that increases (5.5(0.2)%). V100 decreases 2.5(0.0)% and D90, the most signiﬁ cant factor accounting for biochemical control, decreases by 4.6(0.1)%. Regarding Organs at Risk the V100 to the rectum shows an increase of 0.3(0.9) cc, being our constraint of 2 cc.

CONCLUSION: The nomogram provides a good estimation that tends to overcome the inherent uncertainty of the volume study. This technique shows consistency as long as after 4 weeks (when 28% of dose has been delivered) key dosimetric quantities have no signiﬁ cant changes.