Abstract 670P
Background
Limited data on stereotactic re-irradiation for prostate cancer (PC) are available and mainly referred to robotic techniques. We present preliminary data of 25 patients treated with Linac-based SBRT for recurrent PC after previous RT.
Methods
Inclusion criteria were as follows: previous curative or post-operative RT, evidence of biochemical recurrent disease with the radiological (MRI or PSMA/Choline PET-CT) detection of local relapse. A minimum interval of 12 months between the two radiotherapy courses was considered mandatory. SBRT re-irradiation was performed using volumetric modulated arc therapy (VMAT) technique. Toxicity was assessed following CTCAE v4.0.
Results
Between December 2014 and February 2020, 25 patients with median age 75 years (range, 65-89) underwent re-RT for PC and 24 were available for outcomes evaluation. Relapsed disease, detected by Choline PET in 18 cases, PSMA PET in 6 and MRI in one, occurred within the prostate in 14 and prostate bed in 11 cases. Median PSA prior to the SBRT re-irradiation was 1.23 ng/ml (0.47 – 7.81 ng/ml). Four patients received concurrent androgen deprivation therapy. All cases were treated with a median total dose of 30 Gy (25-36 Gy) in 5-6 fractions. Median follow-up was 21 months (2-69 months). Acute toxicity was: G1 in 10.3%, G2 in 10.5% for GU; no GI occurred. For late events, G≥2 GU occurred in 19.7% including one G3 urethral stenosis. For GI toxicity we observed one G1, no G≥2. Three patients died with 1- and 2-year overall survival (OS) rates of 95%. Median PSA-nadir post-SBRT was 0.23 ng/ml (0.07 – 4.27 ng/ml). 1- and 2-year biochemical relapse-free survival (BRFS) and progression-free survival (PFS) rates were 80% and 54.9%; 1- and 2-year ADT-free survival rates were 87% and 75%.
Conclusions
The use of Linac-based SBRT represents a safe and feasible re-treatment option for locally recurrent PC, with one late G3 toxicity reported. Preliminary BRFS, PFS rates and the impact on the potential delay of ADT start are encouraging; more mature data are warranted.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.