ESTRO 2023 - Abstract Book

S1187

Digital Posters

ESTRO 2023

Catherine Institute, Radiotherapy, Avignon, France; 9 Pont de Chaume Clinic, Radiotherapy, Montauban, France; 10 Paoli Calmettes Institute, Radiotherapy, Marseille, France; 11 Cancerology Institute of Strasbourg-Europe, Radiotherapy, Strasbourg, France; 12 Institut Universitaire du Cancer de Toulouse-Oncopole (IUCT-Oncopole), Radiotherapy, Toulouse, France; 13 Pasteur Clinic, Radiotherapy, Toulouse, France; 14 François Baclesse Cancer Center, Radiotherapy, Caen, France; 15 Institut de Cancérologie de l’Ouest René Gauducheau, Radiotherapy, Nantes, France Purpose or Objective High-risk (HR) prostate cancer patients usually receive high-dose radiotherapy (RT) of 76-80 Gy to the prostate and 44-50 Gy to the pelvic lymph nodes using a sequential technique, but data on a simultaneous integrated boost (SIB) technique are lacking. We prospectively evaluated the long-term results of urinary (GU) and digestive (GI) toxicity and survival data of high-dose RT using a SIB technique in HR and very high-risk (VHR) prostate cancer. Materials and Methods Patients were treated using an SIB technique in 34 fractions, at a dose of 54.4 Gy (1.6 Gy/fraction) to the pelvis and seminal vesicles and 74.8 Gy (2.2 Gy/fraction) to the prostate combined to 36 months androgen-depriving therapy in a prospective multicenter study “RCMI pelvis”, (NCT01325961). Urinary and digestive acute ( ≤ 3 months) and late toxicity (up to 5 years) were prospectively collected. Biochemical recurrence-free survival (BCRFS), local-relapse-free survival (LRFS), progression free survival (PFS), metastasis-free survival (MFS) and overall survival (OS) were assessed using a Kaplan-Meier method. Results We recruited 114 patients (37 HR; 77 very high risk). After a median follow-up of 62 months, very few patients experienced acute (M0-M3) (G3-4 GU =3.7%; G3-4 GI=0.9%) or late (M6-M60) severe toxicity (G3-4 GU=5.5 %; G3-4 GI=2.8%). The occurrence of acute G2+ GU or GI toxicity was significantly related to the consequential late G2+ toxicity (p< 0.01 for both GU and GI). At 5 years, BCRFS, LRFS, PFS, MFS and OS were 86.0% [79.4%; 93.2%], 95.8% [91.8%;99.9%], 84.1% [77.2%;91.6%], 87.2% [80.9%;94.0%] and 88.2% [82.1%;94.7%] respectively.

Conclusion SIB radiotherapy at a dose of 54.4 Gy (1.6 Gy/fraction) to the pelvic lymph nodes and seminal vesicles and 74.8 Gy (2.2 Gy/fraction) to the prostate is feasible, leading to satisfying tumor control and reasonable toxicity in HR and VHR prostate cancer.