ESTRO 2024 - Abstract Book

S2417

Clinical - Urology

ESTRO 2024

volumes of the CTVs and their overlap with one another were computed respectively as well as the dice coefficient and the overlap of one CTV with the bladder.

Results:

The mean total volume of the EA and PY CTVS were 126 916mm³ and 104 118mm³, respectively. In 90% of the cases, the EA-defined CTV was larger than the PY-CTV with a mean absolute volume difference of 19.7%. The overlap between CTV and bladder was greater for all EA-CTVs with a mean absolute overlap volume difference of 23,411mm³. On average the EA-CTV showed an overlap of 15.7% and the PY-CTV of 7.1% with the bladder volume. Considering the EA guideline as ground truth the mean Dice similarity coefficient between both CTVs was 0.684 with a standard deviation of 0.069.

Conclusion:

The CTV for sRT defined by the PERYTON guideline achieved its aim to reduce volume. In our limited cohort, the effect was slightly smaller (5 %) compared to the assessment by the initial authors. The reduction of the overlap between CTV and bladder to only half the overlap between EA-CTV and bladder may help to reduce genitourinary toxicity. However, it still must be determined how the expansion to the planning treatment volume and the dose gradients at the anterior bladder will affect dosimetry and ultimately the toxicity.

Keywords: CTV, prostate

References:

[1] Pra AD, Dirix P, Khoo V, et al. ESTRO ACROP guideline on prostate bed delineation for postoperative radiotherapy in prostate cancer. Clin Transl Radiat Oncol. 2023;41. doi:10.1016/j.ctro.2023.100638

[2] Staal FHE, Janssen J, Oprea-Lager DE, et al. Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography – Based Clinical Target Volume Delineation Guideline for Postprostatectomy Salvage Radiation Therapy: The PERYTON Guideline. Int J Radiat Oncol Biol Phys. 2023;0(0). doi:10.1016/j.ijrobp.2023.09.016

1280

Digital Poster

Stereotactic Radiotherapy and ARTA in metastatic Castration-Resistant Prostate Cancer

Chiara L Deantoni 1 , Laura Giannini 1 , Miriam Torrisi 1 , Andrei Fodor 1 , Sara Broggi 2 , Cesare Cozzarini 1 , Antonella De Vecchio 2 , Nadia G Di Muzio 1,3