Daryl Lim Joon, Presenter: Nothing to Disclose

Vincent Khoo MD, Abstract Co-Author: Nothing to Disclose

Angelina Mercuri, Abstract Co-Author: Nothing to Disclose

Aldo Rolfo, Abstract Co-Author: Nothing to Disclose

Kenneth Wan, Abstract Co-Author: Nothing to Disclose

Sarah Gonzales, Abstract Co-Author: Nothing to Disclose

Rebecca Stewart, Abstract Co-Author: Nothing to Disclose

Laura Spiteri, Abstract Co-Author: Nothing to Disclose

Monica Handley, Abstract Co-Author: Nothing to Disclose

Margaret Benci, Abstract Co-Author: Nothing to Disclose

Karen Daly, Abstract Co-Author: Nothing to Disclose

Chris Hamilton, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

Gold seed implantation into the prostate is a technique used to localise the prostate during RT, as pelvic bony anatomy does not account for internal prostate motion. The optimal number of seeds for prostate verification has not yet been defined. Many centres including Austin Health use 3 seeds for verification.The main aim of this study was to assess and compare 1 and 2 seed verification to the standard 3 seed match in the prostate targeting process. The secondary endpoint was to compare various seed combinations to traditional bony verification.

Ten patients with locally advanced prostate cancer were entered into a gold seed verification study. The average age was 71 years, with average PSA and median Gleason scores of 10µg/L and 8 respectively, and T stages from T2a to T3b. Three gold seeds were inserted trans-rectally into the prostate; 1 into the right base, 1 into the left mid gland and 1 into the right apex. All patients were treated to a dose of 78Gy in 39 fractions with IMRT.Daily orthogonal 2D EPIs were taken of each patient in treatment position prior to RT. Elekta I-View template matching software was used to analyse these images. Online pre-treatment verification was performed using the 3 seeds.In the offline setting, matches of dual seed combinations (base and mid gland, base and apex, mid gland and apex), individual seeds (base, mid gland, apex) and bony anatomy were performed for each fraction of all 10 patients.

The average correctional shifts (with ranges) for the different seed combinations in mm were:3 seed: Right-Left (RL) 0.9 (-4.6 to 6.5), Superior-Inferior (SI) -0.3 (-9.8 to 6.3), Anterior-Posterior (AP) -0.3 (-8.6 to 9.1).Base and mid gland: RL 0.9 (-6.1 to 6.5), SI -0.4 (-10.1 to 6.8), AP -0.2 (-8.3 to 9.6)Base and apex: RL 1.1 (-5.3 to 7.3), SI -0.4 (-9.4 to 6.1), AP -0.2 (-9.1 to 9.6)Mid gland and apex: RL 0.9 (-5.8 to 7.3), SI -0.2 (-9.8 to 6.6), AP -0.1 (-8.1 to 12)Base: RL 1.0 (-5.0 to 6.6), SI -0.6 (-10.1 to 7.3), AP -0.3 (-9.1 to 10.4)Mid gland: RL 0.7 (-6.8 to 6.5), SI -0.2 (-10.1 to 6.8), AP -0.2 (-8.6 to 8.9)Apex: RL 1.1 (-4.8 to 6.8), SI -0.1 (-10.1 to 6.6), AP -0.1 (-8.3 to 9.6)Bone: RL 0.9 (-6.8 to 7.0), SI -1.0 (-9.4 to 5.3), AP 0.7 (-13.8 to 8.3)

The study shows that the matching of 1 or 2 gold prostate seeds closely approximates that of 3 seeds. The difference between the 2 seed combinations- notably the base and mid gland- is less than 1mm. The study also illustrates that a 1 seed match more closely approximates the standard 3 seed match than bony verification.The reduction in the number of seeds inserted into the prostate has a number of advantages, including minimisation of morbidity associated with insertion, decrease in insertion time and a reduction in cost.

Lim Joon, D, Khoo, V, Mercuri, A, Rolfo, A, Wan, K, Gonzales, S, Stewart, R, Spiteri, L, Handley, M, Benci, M, Daly, K, Hamilton, C, et al, , Prostate Radiotherapy: Is One or Two Gold Seeds Equivalent to Three?.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/7000407.html