PRO-BOOST-LC: Whole-Gland Boost Strategies Versus SBRT Monotherapy in PSMA-Staged Localized and Locally Advanced Prostate Cancer

Summary

PRO-BOOST-LC is a prospective, multicenter, randomized phase II/III clinical trial for men with localized or locally advanced prostate cancer without lymph node or distant metastases, confirmed using prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT). Radiotherapy is an established curative treatment option for prostate cancer. Several modern radiotherapy strategies can safely deliver high radiation doses to the prostate while limiting dose to surrounding organs. These include stereotactic body radiotherapy (SBRT), high-dose-rate (HDR) brachytherapy, low-dose-rate (LDR) brachytherapy, and combinations of external beam radiotherapy with a prostate boost. However, the optimal dose-escalation strategy for balancing cancer control, treatment-related toxicity, and long-term quality of life remains uncertain in patients staged with modern PSMA PET imaging. The aim of PRO-BOOST-LC is to compare definitive SBRT monotherapy with whole-gland prostate boost strategies delivered after a short course of external beam radiotherapy. Participants will be randomly assigned, according to center capability and patient-level technical suitability, to one of the protocol-defined treatment options. The control group receives SBRT monotherapy. The experimental groups receive external beam radiotherapy followed by one of three whole-gland boost techniques: HDR brachytherapy, LDR brachytherapy, or single-fraction SBRT boost. The primary objective is to determine whether assignment to a prostate boost strategy improves failure-free survival compared with SBRT monotherapy. Failure-free survival includes biochemical recurrence, local or regional progression, distant metastases, progression-driven salvage treatment, or death from any cause. Key secondary outcomes include metastasis-free survival, overall survival, physician-reported treatment-related toxicity, and patient-reported quality of life, including urinary, bowel, and sexual function. Participants will undergo baseline clinical evaluation, PSA testing, prostate MRI, PSMA PET/CT, and quality-of-life assessments. After treatment, participants will be followed regularly with clinical assessments, PSA testing, toxicity evaluation, patient questionnaires, and imaging when clinically indicated. The study is designed to provide long-term evidence on how best to use modern radiotherapy dose escalation for patients with PSMA-staged localized or locally advanced prostate cancer.

Eligibility

Inclusion Criteria:

* Male patients aged ≥18 years.
* Histologically confirmed adenocarcinoma of the prostate.
* Localized or locally advanced prostate cancer classified as cT1-4, cN0, cM0.
* Negative pelvic nodal and distant metastatic disease on baseline PSMA PET.
* NCCN favourbale or unfavourbale intermediate-, high-, or very high-risk disease.
* Candidate for definitive radiotherapy with curative intent.
* ECOG performance status 0-2.
* Baseline PSA available prior to randomization.
* Ability to undergo external beam radiotherapy and brachytherapy or SBRT according to protocol.
* Planned androgen deprivation therapy (ADT) permitted according to protocol-defined risk group.
* Ability to understand and willingness to sign written informed consent.

Exclusion Criteria:

* Evidence of pelvic nodal (cN1) or distant metastatic disease (cM1) on baseline imaging.
* Prior definitive local treatment for prostate cancer, including prostatectomy, brachytherapy, or definitive external beam radiotherapy.
* Prior pelvic radiotherapy for any malignancy.
* Prior systemic therapy for prostate cancer other than protocol-allowed neoadjuvant ADT.
* History of other active malignancy requiring systemic treatment (except adequately treated non-melanoma skin cancer).
* Contraindications to radiotherapy or anesthesia required for brachytherapy procedures.
* Severe uncontrolled comorbidities that would preclude protocol treatment.
* Inability to comply with study procedures or follow-up schedule.

Conditions6

Interventions1

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