3305 - Comorbidity and Bladder Dose-Volume Interplay in Grade-Specific Late Hemorrhagic Radiation Cystitis Following Post-Prostatectomy Radiotherapy: An Asian Cohort
Presenter(s)
H. J. Li1, Y. Chiang2,3, W. C. Huang1, J. K. Wu1, and J. C. H. Cheng1,2; 1Division of Radiation Oncology, Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan, 2Graduate Institute of Oncology, National Taiwan University College of Medicine, Taipei, Taiwan, 3National Taiwan University Cancer Center, Taipei, Taiwan
Purpose/Objective(s): Hemorrhagic radiation cystitis (HRC) is an important toxicity after adjuvant or salvage radiotherapy (RT) following radical prostatectomy. With modern RT techniques, whether grade 2 and grade =3 late HRC share similar determinants remains unclear.
Materials/Methods: We retrospectively analyzed 543 prostate cancer patients who underwent post-prostatectomy RT between 2004 and 2025 (median follow-up 61.9 months). RT was given to prostate bed alone in 271 patients, and to prostate bed plus pelvis in 272 patients. Median dose to prostate bed was 70 Gy (range: 60-74 Gy in 25-39 fractions) and pelvis was 45 Gy (range: 45–50 Gy in 25 fractions) using step-n-shoot intensity modulated or volumetric modulated arc therapy. Late HRC (>90 days after RT) was graded per RTOG criteria; grade 2 was defined as gross hematuria and grade =3 as intervention-requiring hematuria. Bladder dosimetry was available in 518 patients. Comorbidities were defined based on Charlson Comorbidity Index (CCI). Logistic regression identified predictors of grade 2 (vs. 0–1) and grade =3 (vs. 0–2) HRC. Cox proportional hazards modeling assessed time to grade =3 HRC.
Results: Grade 2 and grade 3 HRC occurred in 11.4% and 10.9% of patients, respectively, with no grade 4 events. Median time to grade 3 HRC was 55.5 months (5.3-277.8 months) after RT. In univariate analysis, grade 2 HRC was significantly associated with overall comorbidity burden, reflected by CCI (CCI =1, p=0.003), and specific diseases including chronic kidney disease (CKD, p=0.006) and dementia (p=0.010), but not dose–volume parameters of bladder. In multivariate analysis, CKD was the only independent factor (odds ratio [OR] 12.5, p=0.040). In contrast, grade =3 HRC demonstrated the association with both comorbidity and bladder dosimetry. Although not associated with overall CCI, grade =3 HRC was significantly associated with specific comorbidities including CKD (OR 2.7, p=0.016), coronary artery disease (OR 2.1, p=0.015), and other underlying malignancy (OR 2.0, p=0.029), as well as higher dose-volume exposure of bladder (V65Gy >13% and V70Gy >10%; OR 1.75 and 1.74, p=0.050 and 0.051, respectively). Cox proportional hazards modeling further confirmed independent effects of pelvic RT (hazard ratio [HR] 2.2, p=0.024) and prostate bed dose =70 Gy (HR 4.6, p=0.045) on time to grade =3 HRC.
Conclusion: Grade-specific risk patterns were observed. Grade 2 HRC was linked to systemic vulnerability, whereas grade =3 HRC was driven by both comorbidity burden and irradiated bladder doses/volumes. Cumulative risk of grade =3 HRC was independently associated with bladder dosimetry and pelvis RT. These findings support comorbidity stratification and dosimetric optimization in patients receiving post-prostatectomy RT.