Main Session
Sep 30
PQA 07 - Genitourinary Cancer, Patient Safety, Nursing/Supportive Care

3221 - Prostate Volume Reduction in Prostate Cancer: Predictive Factors after LHRHa Therapy

12:45pm - 02:00pm PT
Hall F
Screen: 11
POSTER

Presenter(s)

Nicolas Feltes, RT Headshot
Nicolas Feltes, RT - Consorci Sanitari de Terrassa, Terrassa, Cataluna

N. Feltes1, S. Paredes1, J. M. Sole1, J. Muñoz2, A. Dominguez2, S. Caballero1, Y. Muñoz1, I. Diaz1, and M. Galdeano Rubio1; 1Hospital Universitario de Terrassa ( CST ), Terrassa, Barcelona, Spain, 2Hospital Universitario Parc Tauli, Sabadell, Barcelona, Spain

Purpose/Objective(s): Androgen Deprivation Therapy (ADT) combined with radiotherapy (RT) is a fundamental approach in the management of localized prostate cancer, as its capacity to reduce prostatic volume can enhance radiotherapy dose distribution and potentially mitigate treatment-related toxicity. This study aimed to determine whether reductions in prostate-specific antigen (PSA) and testosterone levels predict significant prostatic volume reduction (>15%) following ADT with the Luteinizing Hormone-Releasing Hormone Agonist (LHRHa) agent Leupreline-atrigel.

Materials/Methods: A prospective analysis was conducted on 46 patients with localized prostate cancer who underwent LHRHa therapy. Two CT scans were performed before LHRHa initiation and another two months post-treatment. The hormonal therapy consisted exclusively of LHRHa . Three radiation oncologists independently delineated prostatic volume without viewing each other's measurements, totaling 138 pre-treatment and 138 post-treatment measurements. All measurements were performed using systems from contouring and treatment planning software and a precision radiation medicine company to ensure consistency. PSA and testosterone levels were recorded pre- and post-treatment. Statistical analyses included t-tests, Mann-Whitney U tests, and logistic regression modeling to assess correlations between hormonal decline and prostatic volume reduction.

Results:

  • Prostate Volume Reduction by Observer
    • Observer A: 42.58 cc to 35.16 cc (17.4% reduction)
    • Observer B: 50.36 cc to 39.66 cc (21.3% reduction)
    • Observer C: 55.36 cc to 44.73 cc (19.2% reduction)
  • Hormone Level Changes
  • Testosterone: Most patients experienced an 85–90% decrease, reflecting a markedly high level of suppression, yet no significant association was found with prostate volume shrinkage (p = 0.37).
  • PSA: Levels decreased by 75–80% with greater interpatient variability, and similarly, no significant correlation was observed between PSA reduction and volume reduction (p = 0.83).
Logistic regression confirmed that neither PSA nor testosterone decline was a significant predictor of prostatic volume reduction within this cohort.

Conclusion: Although ADT with LHRHa (Leupreline atrigel-Eligard) effectively suppresses PSA and testosterone levels, these reductions do not reliably predict significant prostate volume changes. Baseline prostate characteristics and individual patient factors may have a more substantial impact on volume changes. These findings underscore the need for further research to refine predictive models for prostatic volume reduction, particularly in radiotherapy planning, where accurate estimation of prostate size is crucial for defining the Planning Target Volume (PTV) and minimizing treatment-related toxicity.