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To assess the incidence of both acute and late gastrointestinal (GI) and genitourinary (GU) side effects in patients with organ-confined unfavorable prostate cancer (PCa) treated with single-dose ablative radiotherapy (SDART). Thirty patients enrolled in a single-arm prospective trial (NCT04831983) received 24 Gy SDART to the whole prostate with urethra-sparing and organ motion control. The treatment was delivered on a Linac platform using a 10MV FFF single partial arc. ADT was prescribed as per standard of care. Treatment-related GU and GI toxicities (CTCAE_v5 scale) and QoL outcomes (EORTC QLQ-PR25/C30, IPSS, IIEF 5) were assessed at different time points. Minimal Important Difference (MID) was established as a change of >0.5 pooled SD from baseline. The significance of the differences between QoL outcomes at baseline, 3-month, and last follow-up was tested through the analysis of variances. A logistic regression univariate and multivariate (MVA) analysis was performed to evaluate potential associations between specific patient-related, tumor-related, or treatment-related factors and clinical outcomes. All patients completed the treatment according to the protocol's schedule. The median follow-up was 18 months (range = 6-31), with no ≥G3 side effects observed. Within 3 months post-treatment, there was only one instance of G1 acute GI toxicity, while 2 patients had G2 acute urinary toxicity. G2 late GI and G2 late GU toxicities occurred in 1 and 2 patients, respectively. Late GI toxicity of any grade correlated with maximum rectal dose (P = 0.021), while lower baseline QoL score (P = 0.025), higher baseline IPSS score (P = 0.049), acute GU toxicity (P = 0.029), and acute urinary domain MID (P = 0.045) predicted late GU toxicity of any grade. In MVA, only baseline QoL score (OR 0.95, P = 0.031) and acute GU toxicity (OR 8.4, P = 0.041) remained significant. Significant QoL change was observed only in the urinary domain (P = 0.005), with a median increase from 8 to 17 in the questionnaire score. Late urinary MID correlated with acute urinary MID (P = 0.003), acute QoL MID (P = 0.029), acute GU toxicity (p = 0.030), and lower baseline urinary score (P = 0.033). In MVA, only acute urinary MID predicted late urinary MID (OR 9.7, P = 0.035). All patients were found biochemically controlled at the time of analysis, with median PSA level decreased from 8.05 ng/ml (range = 3.41 – 18.27) at baseline to 0.10 ng/ml (range = 0.01 – 1.46) at the last follow-up. Our findings provide promising data on the feasibility and safety of 24 Gy SDART of the whole prostate with urethra-sparing and organ motion control associated with ADT in organ-confined unfavorable PCa. Long-term follow-up is needed to confirm these results. [ABSTRACT FROM AUTHOR]

Purpose: To assess late gastrointestinal (GI) and genitourinary (GU) side effects in patients with organ-confined unfavorable prostate cancer (PCa) treated with single-dose ablative radiation therapy (SDRT)., Methods and Materials: Thirty patients enrolled in a single-arm prospective trial received 24 Gy SDRT to the whole prostate with urethra-sparing and organ motion control delivered on a Linac platform with a 10 MV flattening filter-free single partial arc. Androgen deprivation therapy was prescribed as per standard of care. Treatment-related acute and late GU and GI toxicities (Common Terminology Criteria for Adverse Events_v5 scale) and quality of life (QoL) outcomes (European Organisation for Research and Treatment of Cancer [EORTC] QLQ-PR25/C30, International Prostate Symptom Score [IPSS]) were assessed at different time points. Minimal important difference (MID) was established as a change of >0.5 pooled standard deviations from baseline. Statistical analysis included analysis of variance and logistic regression., Results: Median follow-up was 18 months (range, 6-31 months), with no ≥G3 late side effects observed. G2 late GI and G2 late GU toxicities occurred in 1 and 2 patients, respectively. GI toxicity of any grade correlated with maximum rectal dose (P = .021). Lower baseline QoL score (P = .025), higher baseline IPSS score (P = .049), acute GU toxicity (P = .029), and acute urinary domain MID (P = .045) predicted GU toxicity of any grade. In multivariate analysis (MVA), only baseline QoL score (odds ratio [OR], 0.95, P = .031) and acute GU toxicity (OR, 8.4, P = .041) remained significant. Significant QoL change was observed only in the urinary domain (P = .005), with a median increase from 8 to 17. Late urinary MID correlated with acute urinary MID (P = .003), acute QoL MID (P = .029), acute GU toxicity (P = .030), and lower baseline urinary score (P = .033). In MVA, only acute urinary MID predicted late urinary MID (OR, 9.7, P = .035)., Conclusions: Our findings provide promising data on the feasibility and safety of 24 Gy whole-gland SDRT with urethra-sparing and organ motion control, in association with androgen deprivation therapy and an adequate prophylactic medication, in organ-confined unfavorable PCa. Long-term follow-up is needed to confirm these results., (Copyright © 2024 Elsevier Inc. All rights reserved.)