PSMA PET-Guided Progression-Directed Radiotherapy for Oligoprogressive Prostate Cancer

Outcomes After PSMA PET-Guided Progression-Directed Radiotherapy, Including SBRT and Brachytherapy, for Oligoprogressive Prostate Cancer: An Ambispective Multicenter Real-World Evidence Cohort Study

PSMA-OLIGO-PRO is a multicenter ambispective observational real-world registry evaluating outcomes after PSMA PET-guided progression-directed radiotherapy for oligoprogressive prostate cancer. The registry includes retrospectively identified patients treated before June 26, 2026 and prospectively enrolled patients from June 26, 2026 onward.

Eligible patients have metastatic hormone-sensitive or castration-resistant prostate cancer, are receiving active systemic therapy, and develop a limited number of new or regrowing lesions while the remaining disease sites are controlled. Oligoprogression is primarily defined by PSMA PET/CT or PSMA PET/MR, with MRI used when clinically appropriate, particularly for intraprostatic, local, or prostate-bed progression.

Participants are not assigned to treatment by the registry protocol. All imaging, systemic therapy, radiotherapy modality, dose, fractionation, and follow-up decisions are made by treating physicians as part of routine clinical care. Progression-directed radiotherapy may include stereotactic body radiotherapy for nodal, bone, visceral, or local lesions, moderately hypofractionated external beam radiotherapy when clinically selected, and brachytherapy when appropriate for intraprostatic, prostate-bed, or selected metastatic oligoprogressive lesions.

The registry evaluates whether treating all identifiable oligoprogressive lesions can delay escalation to a new systemic therapy line, preserve the oligometastatic state, maintain local control, and provide acceptable safety in contemporary PSMA PET-guided practice.

PSMA-OLIGO-PRO is a multicenter ambispective observational real-world evidence registry of patients with prostate cancer who develop limited oligoprogression during otherwise active systemic therapy and undergo lesion-directed radiotherapy in routine clinical practice. The study includes retrospective data from patients treated before June 26, 2026 and prospective data from patients enrolled from June 26, 2026 onward.

Oligoprogression is defined as the occurrence of up to five new and/or regrowing lesions detected on PSMA PET/CT or PSMA PET/MR while other known disease sites remain controlled under ongoing systemic therapy. MRI may be used as a complementary imaging modality when clinically appropriate, especially for intraprostatic recurrence, local recurrence, or prostate-bed progression. Oligoprogression will be categorized according to the ESTRO/EORTC oligometastatic disease framework, including metachronous oligoprogression, repeat oligoprogression, and induced oligoprogression.

Participants are not assigned to any intervention by the registry protocol. The registry does not mandate imaging, systemic therapy, radiotherapy, dose, fractionation, target definition, treatment planning, or follow-up schedules. All clinical decisions are made by treating physicians according to institutional standards, multidisciplinary assessment, available imaging, patient condition, previous treatment history, and local practice.

The exposure of interest is PSMA PET-guided progression-directed radiotherapy delivered with ablative or definitive local intent to all identifiable oligoprogressive lesions. Radiotherapy may include stereotactic body radiotherapy for nodal, bone, visceral, or selected local lesions; moderately hypofractionated external beam radiotherapy when clinically selected; and high-dose-rate or other brachytherapy approaches when appropriate. Brachytherapy may be considered for intraprostatic or prostate-bed oligoprogressive recurrence and, in selected cases, for technically suitable metastatic lesions such as liver metastases, according to institutional expertise and clinical judgment.

The study population includes patients with metastatic hormone-sensitive prostate cancer or metastatic castration-resistant prostate cancer who are receiving active systemic therapy at the time of oligoprogression. Systemic therapy may be continued, modified, or escalated according to routine clinical decision-making. The registry is designed to evaluate whether local treatment of all oligoprogressive lesions can prolong benefit from the current systemic therapy line, delay the need for systemic treatment escalation, and preserve the oligometastatic state.

The primary endpoint is time to next systemic therapy escalation, defined as the time from the start of the index progression-directed radiotherapy course to initiation of a new systemic therapy line. Key secondary endpoints include time to polymetastatic progression, radiographic progression-free survival, overall survival, local control of treated lesions, repeat oligoprogression, use of subsequent lesion-directed therapy, patterns of disease progression, and treatment-related adverse events.

Safety will be assessed using adverse events recorded in routine clinical care and graded according to CTCAE version 5.0 when sufficient information is available. Acute and late adverse events will be described separately. Exploratory analyses will evaluate clinical, imaging, disease-related, and treatment-related factors associated with delayed systemic therapy escalation, durable local control, and preservation of an oligometastatic disease state.

Because this is an observational registry, the study aims to describe real-world outcomes after contemporary PSMA PET-guided progression-directed radiotherapy rather than test a protocol-assigned treatment strategy. The results are intended to support patient selection, multidisciplinary decision-making, and future prospective studies of oligoprogressive prostate cancer.

Inclusion Criteria:

• Age 18 years or older.
• Diagnosis of prostate cancer.
• Metastatic hormone-sensitive prostate cancer or metastatic castration-resistant prostate cancer.
• Receiving active systemic therapy at the time of oligoprogression.
• Oligoprogression defined as up to five new and/or regrowing lesions detected on PSMA PET/CT or PSMA PET/MR, with other known disease sites remaining controlled.
• Planned or completed PSMA PET-guided progression-directed radiotherapy to all clinically relevant oligoprogressive lesions as part of routine clinical care.
• Radiotherapy may include stereotactic body radiotherapy, moderately hypofractionated external beam radiotherapy, brachytherapy, combined external beam radiotherapy and brachytherapy, or mixed-modality radiotherapy, when clinically appropriate.
• Availability of baseline clinical, imaging, treatment, and follow-up data sufficient for registry endpoints.

Exclusion Criteria:

• Polymetastatic progression not consistent with an oligoprogressive state at the time of index radiotherapy.
• More than five new or regrowing lesions at the index oligoprogression episode.
• Radiotherapy delivered with purely palliative symptom-control intent rather than progression-directed local control intent.
• Lack of sufficient clinical, imaging, treatment, or follow-up information for endpoint assessment.
• Any condition that, in the opinion of the treating physician or investigator, makes registry inclusion inappropriate.