ESTRO 2024 - Abstract Book

S2493

Clinical - Urology

ESTRO 2024

MFS at 1, 2 and 5 years was 100%, 94.4% and 80% respectively. On the multivariate analysis, factors associated with poor MFS were PSA levels higher than 1.4 ng/mL before radiotherapy (p:0.005; HR 1.12; CI 1.03-1.22) and clinical stages ≥ T3a (p:0.028; HR 2.83;CI 1.11 – 7.16). Table 2.

The 5- year OS was 81.2%. We identified clinical staging ≥ T3a as a factor associated with worse OS (p:0.024; HR: 4.22; IC: 1.21-14.71) while completing 24 months of ADT was associated with improved OS (p:0.039; HR:0.331; IC:0.116 0.94).

Toxicity was low, with acute urinary toxicity ≥ 3 and chronic toxicity rates of 2.2% and 1.61%. No acute digestive toxicity ≥ 3 was observed, with 4.8 % chronic toxicity. Treatment planning was not associated with toxicity.

We observed 5 local recurrences, all with associated extra-prostatic dissemination. Only five patients (4%) had infield nodal recurrence. Four of them were diagnosed with PSMA or Choline PET-CT. All of them had multiple metastatic progression both in lymph nodes and bones. We observed distant dissemination in 28 patients (22.6%). The pattern of dissemination was polymetastatic in all cases, with 39.3% nodal (M1a), 28% bone, and 32% mixed (bone and nodal). Only two patients had visceral involvement.

Of the 28 patients who failed at both pelvic and distant levels, 20 had completed ADT. 71.42% of all progressions were castration-resistant.

Conclusion:

• Nodal irradiation with dose-escalation achieves very satisfactory results in terms of BRFS, MFS and OS without an increment of clinically relevant toxicity. • Our series has not shown any differences between prophylactic doses and dose-escalation on the affected nodes. • Our MFS results are better than the comparison arm on STAMPEDE study. Therefore, we believe that adding pelvic irradiation to STAMPEDE regime could be a feasible and safe approach to improve results and maybe change the current standard of care.

Keywords: Prostate, dose-escalation, STAMPEDE

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