S1292
Clinical - Urology
ESTRO 2026
Conclusion: PSA monitoring after prostate RT is inconsistent, with poor guideline adherence. Early, consistent monitoring in the first year post-RT is associated with improved BCR outcomes. Non-compliance likely reflects socioeconomic barriers, centre-level factors, and lost records. Findings support current recommendations, but highlight the need for better implementation, with contemporary data needed to confirm. References: 1. Frydenberg M, Stricker PD, Kaye KW. Prostate cancer diagnosis and management. Lancet. 1997;349(9066):1681-1687. doi:10.1016/S0140- 6736(96)07393-X2. Casado E, Amis ES. Prostate Cancer 2000. Contemp Diagnostic Radiol. 1999;22(22):1-5. doi:10.1097/00219246-199922220- 000013. Bott SR, Ng KL. Prostate Cancer. Prostate Cancer. Published online 2021:1-174. doi:10.36255/exonpublications.prostatecancer.2021 Keywords: prostate cancer, PSA follow-up, guideline Digital Poster 4213 Contouring variability of boost volumes for radiotherapy quality assurance (RTQA) (PIVOTALboost trial): effects on the minimum boost dose Alexander Batty, Rhiju Chatterjee, Helen Mayles, Isabel Syndikus Clinical Oncology, Clatterbridge Cancer Centre, Liverpool, United Kingdom Purpose/Objective: For the PIVOTALboost trial RTQA exercise, trial clinicians contoured a prostate and boost case prior to recruiting patients (1). We examined the interobserver contouring variability and how this changes the dose to the boost (CTVb) and prostate (PTVp). Higher minimum dose to CTVb has been associated with better local control (2). Material/Methods: Three lead clinicians with experience in focal boosting agreed on consensus gold standard contours (GS). The investigators were provided with a clinical history, the diagnostic multiparametric MRI (T2W, and ADC map) and contoured the GTV and CTVp on CT planning images. We had 61 submissions from 35 UK cancer centres. Geometric similarity of contours was compared to the GS_GTV and GS_CTVp with the Dice similarity coefficient (DSC), the 95% Hausdorff Distance (HD), the centre of mass difference and the volume difference. A median contour was generated at a voxel level from all submitted contours and this was compared with GS. The CTVb dose (GTVb+3mm margin) and the PTVp dose (CTVp+3mm margin) were 67Gy/60Gy in 20 fractions. Equivalent VMAT
Compliance rose from 0% in 2004 to 35.8% in 2008 (first NICE-guideline), remaining 20-30% until 2014 (second NICE-guideline). During 2020-2024, compliance was ≤ 2%, likely reflecting COVID disruption. In the matched cohort (n=234), compliant patients showed improved BCR-free survival (p=0.0084, Figure 2). Compliance remained independently prognostic in multivariable Cox regression adjusting for risk, age, T-stage, Gleason- grade-group, baseline-PSA, and ADT (HR 0.39[0.23- 0.64], p<0.001).
Made with FlippingBook - Share PDF online