Observational Study on Extreme Hypofractionation for Localized Prostate Cancer

Inclusion criteria

• men ≥ 18 years
• histologically confirmed clinically localized adenocarcinoma of the prostate
• intermediate- or high-risk PCa, defined as

OR at least one of the following criteria:

• clinical stage: cT2a-c, cT3a or cT3b (AJCC 7th edition)
• Gleason Score ≥ 7 (ISUP grade group 2 or higher)

OR at least two of the following criteria:

• clinical stage: cT1c (AJCC 7th edition)
• Gleason Score ≥ 7 (ISUP grade group 2 or higher)
• calculated risk for lymph node involvement (Roach formula) <35%.
• no evidence of disease spread beyond the prostate and/or seminal vesicles
• imaging with mpMRI of the prostate and pelvis (compliant with the PIRADS v2.1 guidelines) within 90 days prior to registration, or required to be performed after registration to the trial
• ability to understand, and willingness to sign, the written informed consent
• willingness to comply with scheduled visits, treatment, and other procedures

Exclusion criteria

• prior pelvic irradiation (external beam radiotherapy or brachytherapy)
• previous radical prostatectomy, cryosurgery, or HIFU for prostate cancer
• previous or concurrent cytotoxic chemotherapy for prostate cancer
• patients with neuroendocrine or small cell carcinoma of the prostate
• clinical stage cT4 (invasion of adjacent organ like bladder or rectum, visualized on mpMRI and/or ultrasound and endoscopy) (AJCC 7th edition)
• significant urinary obstruction of other voiding symptoms (IPSS > 18) is allowed, however should be discussed with the principal investigator and left to the discretion of the treating physician
• high risk of lymph node involvement, as calculated with the Roach formula ≥ 35% (https://www.evidencio.com/models/show/1144) Of note, in case of ambiguity of regional lymph node involvement on CT or MRI findings (when Roach formula is < 35%, and all other eligibility criteria are met), dedicated imaging with PSMA PET-CT or extended pelvic lymph node dissection must be obtained to rule out lymph node involvement
• evidence of distant metastases (based on CT scan, MRI of the pelvis, bone scan within 90 days prior to registration; if the bone scan is suspicious but not unequivocal, dedicated X-ray and/or MRI must be obtained to rule out metastasis)
• contraindications to MRI according to the Radiology Department guidelines (metal implants, noncompatible cardiac device, deep brain stimulators, cochlear implants, metallic foreign body in the eye or aneurysm clips in the brain, severe claustrophobia).
• World Health Organization (WHO) performance score > 2
• patients with severe inflammatory bowel disease rendering radiotherapy impossible (active Crohn's Disease or Ulcerative Colitis), or patients known with ataxia telangiectasia
• implanted hardware or other material that would prohibit appropriate treatment planning or treatment delivery, in the investigator's opinion
• prior or concurrent invasive malignancy (except non-melanomatous skin cancer) or lymphomatous/hematogenous malignancy unless continually disease-free for a minimum of 5 years.

(carcinoma in situ of the bladder or oral cavity is permissible)