Po‐Thur Eve General‐31: Dosimetric Impact of Planning a Boost within a Boost in Permanent Seed Implants

• Published in: Medical Physics 2006-07, Vol.33 (7), p.2666-2666
• Main Authors: Beaulieu, L, Aubin, S, Varfalvy, N, Lessard, E, Pouliot, J, Vigneault, E, Martin, AG
• Format: Article
• Language: English
• Subjects: Annealing; Cancer; Dosimetry; Lead
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.2244658

Purpose: To investigate the dosimetric impact on the target volume, boost volume (BV) and urethra of performing limited volume boosts in seed implants. Method and Materials: 35 localized prostate cancer patients with detailed biopsy results were treated with permanent seed implants Personalized plans in which BV corresponding to regions of positive biopsy were generated intra‐operatively based on a simulated annealing inverse planning algorithm. The dose objectives are 144 Gy to the prostate with a 3–4 mm margin, 2/3 (1/3) of the prostate covered by 150% (200%) of the prescription dose (PD), urethra V150 less than 10% and D5 should below 220 Gy. Finally, 100% of BV should receive 150% PD (or 216 Gy). Results: Comparing plans without and with BV show no significant change in the number of seeds, needles, prostate V100 and V200. Prostate V150 (D90) show significant differences increasing from 65% (187Gy) to 70% (191Gy). By forcing the coverage of the BV, the 150% isodose lines (which extend outside the prostate) shift inside of the prostate. Small increase in prostate V150 leads to significant increases of the BV V150 from 79% to 94%. BV do not translate to higher urethra doses. Thus multiple seed reconfigurations inside the prostate are achievable to cover BV. Conclusion: Specific areas within the prostate can be boost to receive 150% of the PD with no impact on the urethra. The plans lead essentially to a rearrangement of the seed positions. Potential radiobiological advantages could be obtained at no cost (procedure or time).