116 - Two-Year Clinical Outcomes Following Ablative Radiotherapy for Unfavorable Prostate Tumors (ABRUPT)
Presenter(s)
C. Chissotti1,2, V. Faccenda3,4, F. Ferrario2,5, R. R. Colciago2, L. De Sanctis6, G. Rossano6, E. De Ponti3, D. Panizza3, and S. Arcangeli2; 1Department of Radiation Oncology, ASST Lecco, Lecco, Italy, 2University of Milan Bicocca - School of Medicine and Surgery, Milan, Italy, 3Fondazione IRCCS San Gerardo dei Tintori - Medical Physics, Monza, Italy, 4Fondazione IRCCS San Gerardo dei Tintori - Medical Physics Department, Monza, Italy, 5IRCCS-SAN GERARDO DEI TINTORI, MONZA, Italy, 6School of Medicine and Surgery, University of Milan Bicocca, Milano, Italy
Purpose/Objective(s):
To investigate clinical outcomes in patients with organ-confined, unfavorable prostate cancer (PCa) treated with single-dose ablative radiation therapy (SDRT).Materials/Methods:
Thirty patients enrolled in a single-arm prospective trial (NCT04831983) received 24 Gy SDRT to the whole prostate with urethra sparing and organ motion control, delivered on a Linac platform using a 10 MV flattening filter-free single partial arc. Androgen deprivation therapy (ADT) was prescribed as per standard of care. Treatment-related acute and late genitourinary (GU) and gastrointestinal (GI) toxicities using the Common Terminology Criteria for Adverse Events v5 scale, and quality of life (QoL) outcomes (EORTC QLQ-PR25/C30 and International Prostate Symptom Score [IPSS]) were evaluated at multiple time points. Minimal clinically important difference (MCID) was defined as a change of >0.5 pooled standard deviations from baseline. Statistical analyses included analysis of variance and logistic regression.Results: The median age was 77 years (62–84) and the median initial PSA level was 8.0 ng/mL (3.4–18.3). Intermediate unfavorable and high-risk PCa accounted for 33% and 67%, respectively. 97% of patients received ADT for a median duration of 12 months (6–24). After a median follow-up of 24 months (18–42), no = grade 3 toxicity was observed. Late grade 2 GU and GI toxicity occurred in 5 (16.7%) and 2 (6.7%) patients, respectively. In the MCID analysis, the only statistically significant change between baseline, 3 months after SDRT, and last follow-up was observed in the urinary domain (P = .007), with a median score increasing from 8 (0–25) to 17 (0–46) at 3 months, and settling at 15 (0–46) thereafter. Late urinary MCID significantly correlated with acute urinary MCID (P = .012), a higher PR25 urinary domain score at 3 months (P = .019), and an elevated IPSS score at 3 months (P = .032). In the multivariate analysis (MVA), acute urinary MCID was the only predictive factor for late urinary MCID (P = .022). Late GU toxicity of any grade was significantly associated with acute GU toxicity of any grade (P = .042), acute QoL score (P = .014), and acute PR25 urinary domain score (P = .025). GI toxicity of any grade correlated with the maximum rectal dose (P = .021). At last follow-up all patients were biochemically controlled with a median PSA of 0.16 ng/mL (0.01–0.62 ng/mL), and 83.3% had recovered testosterone levels (median: 3.0 ng/mL, 0.1–11.0).
Conclusion: Our findings provide reassuring evidence on the feasibility and safety of 24 Gy SDRT to the whole prostate with urethra sparing and organ motion control, in association with ADT, in patients with organ-confined unfavorable PCa. Longer follow-up is needed to exclude long-term adverse effects and assess treatment’s efficacy.