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SU‐FF‐T‐112: Boost Within a Boost in Permanent Seed Implants: Dosimetric and Clinical Impact
Author(s) -
Beaulieu L,
Aubin S,
Varfalvy N,
Lessard E,
Pouliot J,
Vigneault E,
Martin AG
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2241037
Subject(s) - prostate , medicine , prostate cancer , nuclear medicine , urethra , prostate biopsy , urology , cancer
Purpose: Study the dosimetric and clinical impact on the target volume, boost volume (BV) and urethra of performing 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. A second plan was generated for each patient without the BV. 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 (p>0.37). Prostate V150 and D90 show significant differences increasing from 65% to 70% and from 187 Gy to 191 Gy. By forcing the coverage of the BV, the 150% isodose lines (which extend outside the prostate) shift inside of the prostate. This small increase in prostate V150 leads to significant increases of the BV V150 from 79% (lowest 42%) to 94% (lowest 86%). BV do not translate to higher urethra doses (V150 and D5). BV are relatively small compared to the prostate V150 volumes (average ratio of 18%). 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. Large volumes of these dose levels are inherent to the procedure. The plans lead essentially to a rearrangement of the seed positions. Potential radiobiological advantages could be obtained at no cost (procedure or time).