ESTRO 2020 Abstract Book

S612 ESTRO 2020

PO-1162 Post hifu salvage radiotherapy in locally relapsed prostate carcinoma: a mono-institutional analysis M. Rigo 1 , R. Mazzola 2 , G. Napoli 2 , N. Giaj-Levra 2 , V. Figlia 2 , L. Nicosia 2 , F. Ricchetti 2 , C. Bellorofonte 3 , F. Cuccia 2 , F. Alongi 2 1 IRCCS Sacro Cuore Don Calabria Hospital- Cancer Care Center, Advanced Radiation Oncology Department, Negrar di Valpolicella VR, Italy ; 2 IRCCS Sacro Cuore Don Calabria Hospital- Cancer Care Center- Negrar- Verona- Italy, Advanced Radiation Oncology Department, Negrar, Italy ; 3 Columbus Clinic Center, Urology, Milano, Italy Purpose or Objective To evaluate tolerance, feasibility and biochemical control rates of salvage external beam radiotherapy (EBRT) in patients with local relapse from prostate cancer after high intensity focused ultrasound (HIFU) as primary treatment. Material and Methods This is a retrospective analysis of 24 patients with histological proven prostate adenocarcinoma treated with 1 or more HIFU sessions between 2007 and 2018. All patients presented biochemical failure after HIFU (according to the Stuttgard definition) and so 11C choline PET or 68Ga/18F PSMA PET was performed for restaging and treatment planning. The median interval between HIFU and EBRT was 39 months (3 – 136 months) and the median PSA before EBRT was 6.94 ng/mL (2.07 – 91 ng/ml). Salvage EBRT was performed with moderate hypofractionation schedule in 28 fractions (n=16) or with extreme hypofractionation schedule in 5 fractions (n=8) by means image-guided volumetric modulation arc therapy (VMAT-IGRT). All patients were treated with EBRT to the residual prostate. In case of moderate hypofractionation (MHRT), the median dose was 71.4 Gy (71.4 -74.2 Gy) and 7 patients concomitantly received pelvic lymph node EBRT (50.4 – 51.8 Gy). In case of extreme hypofractionation (SBRT), the residual prostate with a median dose of 32.5 Gy (30 – 35 Gy) was irradiated. Five patients (21%) received concomitant/adjuvant androgen deprivation therapy (ADT). Primary endpoints were feasibility and toxicity associated to hypofractionated EBRT after HIFU failure. Genito-urinary (GU) and rectal and bowel toxicity (GI) were scored by common terminology criteria for adverse events version 4 (CTCAE V.4) scale. Biochemical response was assessed by ASTRO Phoenix criteria. Results The median follow-up after EBRT was 28 months. The median PSA nadir was 0.26 ng/mL (0.01- 12.05 ng/ml) and it was obtained in a median of 17 months. In case of moderate hypofractionation, the median PSA nadir was 0.15 ng/mL (0.01 – 2.48 ng/mL) and occurred within a median time of 19 months (3 – 59 months). In case of extreme hypofractionation, the median PSA nadir was 0.64 ng/mL (0.12 – 12.05 ng/mL) and occurred within a median time of 8 months (3 – 27 months). No grade 3 higher acute or late toxicity after EBRT was observed. Only 3 patients presented with G2 acute gastrointestinal toxicity (actinic proctitis), out of them one was treated with extreme hypofractionation. Twelve (50%) of patients experienced acute G1 GU toxicities: 8/16 of men treated with moderate hypofractionation and 4/8 of men treated with extreme hypofractionation. At the time of follow-up a complete local control of disease was achieved in 23/24 patients (96%). Conclusion Our data confirm the feasibility and the low toxicity of salvage EBRT with both schedules of treatment after HIFU failure. The findings of low acute toxicity and good biochemical control rates are encouraging, but larger number of patients and a longer follow-up are needed to confirm these results.

analyzed. 3-year bPFS in low, favorable intermediate, unfavorable intermediate, high, and very high group were 100%, 100%, 100%, 94.6% and 84.1% respectively. 5-year bPFS in low, favorable intermediate, unfavorable intermediate, high, and very high group were 100%, 100%, 100%, 90.4% and 80.6% respectively. The incidence of acute ≥ grade 2 GU and GI toxicity were 9.3% and 5.6% respectively and the incidence of late ≥ grade 2 GU and GI toxicity were 7.1% and 5.2% respectively. In multivariate analysis, no association was found between dose fractionation or antiplatelet/anticoagulant drugs and ≥ grade 2 toxicity.

Conclusion Definite VMAT in prostate cancer results in an impressive survival outcome which is comparable to previous studies with conventional fractionation or moderate hypofractionation; whereas, the overall rates of acute and late GU and GI toxicity were relatively low.