Background
Dual-tracer positron emission tomography/computed tomography (PET/CT) with a 68Ga-labelled prostate-specific membrane antigen (PSMA) ligand and 18F-fluorodeoxyglucose (FDG) improves detection of metastatic heterogeneity and burden in patients with nonmetastatic prostate cancer (nmPCa). However, there is limited prospective evidence regarding its impact on the efficacy of stereotactic body radiotherapy (SBRT).
Objective
To evaluate metastasis-free survival (MFS) and toxicity after SBRT to dual-tracer PET/CT-detected metastases in patients with nmPCa and early prostate-specific antigen (PSA) progression on androgen deprivation therapy (ADT; PSA ≤2 ng/ml).
Design, setting, and participants
Patients were prospectively screened using dual-tracer PET/CT between April 2019 and October 2020. SBRT was recommended for patients with five or fewer nonvisceral metastases (SBRT group). Patients without detectable metastases (N−/M− group) and those who refused SBRT (ADT group) continued to receive ADT. Patients were followed with conventional imaging.
Intervention
SBRT to each PET/CT-detected metastasis.
Outcome measurements and statistical analysis
Kaplan-Meier methods were used to determine MFS. Toxicity was evaluated using Common Terminology Criteria for Adverse Event v4.0.
Results and limitations
Seventy-four consecutive patients were screened. The median PSA and PSA doubling time were 0.59 ng/ml and 4.56 mo, respectively. Overall, 54 patients had metastases and 17 had PSMA-/FDG+ disease. Seven patients were excluded from the MFS analysis, including two with a history of abiraterone treatment and five with more than five metastases. The median follow-up was 21.4 mo. The ADT group had shorter MFS than the SBRT group (11.0 mo vs not reached; hazard ratio [HR] 4.69, 95% confidence interval [CI] 2.92–25.0; p < 0.001) and the N−/M− group (11.0 mo vs not reached; HR 8.78, 95% CI 4.04–40.30; p < 0.001). There was no significant difference in median MFS between the SBRT group and the N−/M− group (p = 0.261). A PSA response >90% was achieved by 86% of patients in the SBRT group. There were no grade ≥3 adverse events after SBRT. The nonrandomized design is the major study limitation.
Conclusions
Dual-tracer PET/CT-guided SBRT delivered superior local control rates in comparison to ADT alone and had minimal toxicity.
