Dose Escalation: Solid Tumors

PRO-BOOST-N is a prospective, multicenter, randomized phase II/III clinical trial for patients with prostate cancer and pelvic lymph node involvement (cN1M0) confirmed by PSMA PET/CT, without distant metastatic disease. Patients with PSMA PET-staged node-positive prostate cancer are potentially curable, but remain at substantial risk of distant progression despite contemporary treatment with radiotherapy, long-term androgen deprivation therapy, and, when appropriate, androgen receptor pathway inhibitors. The optimal way to intensify radiotherapy to the prostate and PSMA PET-positive pelvic lymph nodes remains uncertain in the era of modern molecular imaging. All participants receive a standardized ultrahypofractionated whole-pelvis radiotherapy backbone delivered in five fractions, combined with long-term systemic therapy according to contemporary clinical practice. The study uses a 2 x 2 factorial randomized design to evaluate two treatment questions. The primary comparison evaluates whether prostate dose escalation improves metastasis-free survival compared with no additional prostate boost. Patients assigned to prostate boost receive one of three protocol-defined boost techniques: high-dose-rate brachytherapy, low-dose-rate brachytherapy, or single-fraction SBRT. If more than one prostate boost technique is available at the treating center and technically suitable for the patient, the boost technique is assigned by embedded subrandomization. The key secondary, hierarchically tested comparison evaluates nodal dose escalation by comparing two predefined dose levels to PSMA PET-positive pelvic lymph nodes. Organ-at-risk-driven nodal dose de-escalation is permitted within the higher-dose arm when required for patient safety and protocol compliance. The primary endpoint is metastasis-free survival (MFS) . Secondary endpoints include overall survival (OS), radiographic progression-free survival (rPFS), intraprostatic and regional nodal control, time to castration-resistant prostate cancer, time to next systemic therapy, treatment-related adverse events graded according to CTCAE version 6.0, and patient-reported quality of life, including urinary, bowel, sexual, and global health domains. PRO-BOOST-N aims to determine the optimal radiotherapy intensification strategy for patients with PSMA PET-staged node-positive prostate cancer by prospectively evaluating prostate-directed and nodal-directed dose escalation within a modern, standardized radiotherapy platform.

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.