Efficacy of Repeat Stereotactic Radiation in Patients With Intraprostatic Tumor Recurrence

Inclusion Criteria:

* Biochemical recurrence occurring at least 2 years after external radiotherapy for prostatic adenocarcinoma by the Phoenix definition (PSA nadir + 2 ng/mL)
* T1-T2c and PSA ≤20 ng/mL and Gleason score ≤7 at initial diagnosis of prostate cancer before the initial/first treatment.
* Recurrence of prostatic adenocarcinoma proven by histology following radiotherapy by transrectal or transperineal sextant biopsies of the two lobes of the prostate, with a minimum of 12 biopsies, irrespective of Gleason score. Biopsies of the seminal vesicles are optional.
* Clinical stage T1-T2 on relapse; unilateral extracapsular extension (T3a) on MRI permitted except posteriorly relative to the rectum
* Estimated clinical target volume (CTV) / prostate volume \< 0.5 based on imaging and biopsies
* Pelvic and prostatic assessment by multiparametric MRI- Absence of pelvic or metastatic recurrence proven by choline PET scan
* Performance status World Health Organization (WHO) 0-1
* PSA level ≤10 ng/mL at baseline (before salvage-SBRT)
* PSA doubling time \>10 months
* International Prostate Cancer Score (IPSS) ≤12
* Uroflowmetry with a maximum flow rate \>10 mL/s, a postvoid residual urine volume \<150 mL, and a urine volume \>150 mL.
* No other anti-cancer treatment since the external radiotherapy administered as first-line treatment
* No other anti-cancer treatment planned for the current recurrence
* No contraindication to fiducial marker implants; haemostatic disorders must be corrected before implantation
* Age \>18 years
* Life-expectancy greater than or equal to 5 years (Lee scale)
* Patient registered with a health insurance system
* Patient who has signed the informed consent form
* Patients willing and able to comply with the scheduled visits, treatment plan, laboratory tests, and other study procedures indicated in the protocol.

Exclusion Criteria:

* Lymph node or metastatic spread
* Late post-radiotherapy urinary or gastrointestinal toxicity of grade ≥2 (following primary radiotherapy)
* Other cancers in the last 5 years except for non-melanoma-type skin cancer
* History of inflammatory bowel disease
* Anticoagulant treatment
* Contraindications to undergoing MRI
* Prostate volume \>80 cc
* Transurethral resection of the prostate (TURP) in the 6 months before registrations
* Presence of rectal telangiectasia grade 3 classified by the Vienna Rectoscopy Score (obligatory rectoscopy)
* Previous rectal surgery
* Patients unable to undergo medical follow-up in the study for geographical, social or psychological
* Person deprived of their liberty or under protective custody or guardianship
* Patients enrolled in another therapeutic study

All patients during the SBRT planning with a ratio of clinical target volume (CTV) / prostate volume \>0.5 will be withdrawn from the study. These patients will be considered as not evaluable and will not be treated within the context of the study.