PSMA-Guided Radiotherapy Offers Promise in Men with Oligorecurrent Prostate Cancer

Introduction

Oligometastases is a state of cancer with a limited number of metastases in only one or few sites. First-line treatment of patients with recurrent, metastatic prostate carcinoma includes hormone therapy with or without additional systemic therapies. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) enables the detection of small metastases undetectable by conventional imaging techniques.  

Aim

The study classifies the type and localization of metastases and assesses the clinical outcome after stereotactic body radiation therapy (SBRT) for patients with oligorecurrent prostate cancer detected by PSMA-PET/CT imaging.

Method

Study Design

• Retrospective cohort study

Treatment Strategy

• A total of 86 patients with recurrent, oligometastatic prostate carcinoma were identified by PSMA-PET/CT
• They were treated with image-guided radiotherapy of their metastases.
• The sites of relapse were characterized

Endpoints

• Overall survival (OS)
• Biochemical progression-free survival (bPFS)
• Androgen deprivation therapy (ADT)-free survival

Results

• PSMA-PET/CT detected 168 PSMA-positive lesions in a total of 86 patients
• Only 1 metastasis was reported in 54%, 2 metastases in 25.9% and 3 or more metastases in 20.1%
• Out of a total of 168 metastases, 37% were bone metastases, 48% were pelvic nodal metastases, and 15% were nodal metastases outside of the pelvis.
• After PSMA-guided radiotherapy, a biochemical response was detected in 83%
• Tumor lesions exhibited a significant decrease in the standard uptake value (SUV) from 7.45 to 0 after irradiation
• After a median follow-up of 26 months, 88.4% were still alive
• The 2-year and 3-year OS rates were 95.7% and 83.7% respectively
• The 2-year and 3-year bPFS were 85.1% and 55.1%, respectively.
• The median time of ADT-free survival was 13.5 months.
• Patients receiving more than 24 fractions had better clinical and survival outcomes as compared to those receiving 9 or fewer fractions of radiation

Conclusion

• Prostate-specific membrane antigen (PSMA)-guided radiotherapy offers satisfactory clinical outcomes in men with oligorecurrent prostate cancer and seems a promising therapeutic tool
• However, prospective, randomized trials are warranted to determine if this approach provides a survival advantage

Eur J Nucl Med Mol Imaging. 2020 May 13. Doi: 10.1007/s00259-020-04777-z.