ESTRO 2023 - Abstract Book

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ESTRO 2023

them (2.2%) receiving three re-irradiations. Among the 38 patients with updated follow-up data, 8 (21.1%) resulted free from disease at last contact. Progression of disease (PD) was observed in 30 out of 38 patients (78.9%) with 16 clinical and 14 biochemical progressions. Median time to clinical and biochemical progression were, respectively, 15.5 (IQR: 10.7 – 21.9) and 14.0 months (IQR: 10.7 – 41.9). Of them, only one patient experienced polyprogression. Regarding acute toxicity outcomes, no genitourinary (GU) events higher than grade (G) 1 and no gastrointestinal (GI) events higher than G2 occurred. During follow-up, no patients but three experienced GU/GI events higher than 2. One patient experienced G3 GU maximum toxicity with implantation of an artificial urinary sphincter after worsening of urinary incontinence, which however decreased to G0 at last contact. Two patients experienced late G4 GU toxicity: one of them had acute urinary retention with bladder catheter positioning – turning into G2 at last follow-up; the other one underwent internal urethrotomy. None of the patients experienced late GI toxicity.

Conclusion Salvage stereotactic re-irradiation treatment for locally recurrent PCa seems to be a safe and promising strategy to control bed recurrence. Further studies and longer follow-up are warranted to confirm these preliminary findings.

PO-1499 Extracranial stereotactic radiotherapy in low and favourable intermediate risk prostate cancer

V. Navarro Aznar 1 , A. Méndez Villamón 1 , M.D.M. Puertas Valiño 1 , C. García Aguilera 1 , M. Cerrolaza Pascual 1 , A. Lanuza Pascual 1 , J.M. Ponce Ortega 1 , C. Colom 1 , B. Garcia Gimeno 1 , M. Tejedor Gutiérrez 1

1 Miguel Servet Hospital, Radiation Oncology, Zaragoza, Spain

Purpose or Objective To analyse overall survival (OS); cancer-specific survival (CSS); disease-free survival (DFS) and acute and chronic toxicity in patients with low and favourable intermediate localised prostate cancer treated with extracranial stereotactic radiotherapy (SBRT). Materials and Methods We retrospectively analysed 466 patients with localised low and favourable intermediate risk prostate cancer treated with SBRT between February 2014 and October 2022. All received dietary recommendations and rectal preparation with enema the night before the planning CT scan, which was performed with diuresis control, immobilisation system with wedge under knees and abdominal compressor with 3mm cuts. Intensity modulated radiotherapy was applied using a Linear Electron Accelerator with a photon beam energy of 6MV, administering 35Gy in 7 sessions over the prostate volume with a uniform margin of 4mm to conform the planning target volume (PTV) Weekly follow-up was carried out during the treatment and once it was finished: at one month, 3 months, to continue with six-month follow-up. Toxicity was analysed according to genitourinary and gastrointestinal RTOG scale and IPSS. Results The median age was 72 years. 68% had received previous hormone treatment. 39% were low risk and 61% favourable intermediate risk. With a median follow-up of 44 months, DFS was 94.64% and CSS was 99.57% with an OS of 89.48%. The IPSS score increased a median of 2 points and normalised after 6 months to baseline values. 49.14% experienced acute genitourinary toxicity G1, 5.36% G2, and 0.43% G3. Acute G1 gastrointestinal toxicity was experienced in 7.3%, G2 in 0.86% and G3 in 0.21%. After 6 months, G1 genitourinary toxicity was reported in 3.06%, G2 in