In Canada and across the globe, access to PSMA PET/CT is limited and expensive. For patients with biochemical recurrence (BCR) after treatment for prostate cancer, novel strategies are needed to better stratify patients who may or may not benefit from a PSMA PET scan. The role of the free-to-total prostate-specific antigen (PSA) ratio (FPSAR) in posttreatment prostate cancer, specifically in the PSMA PET/CT era, remains unknown. Our aim in this study was to determine the association of FPSAR in patients referred for ¹⁸F-DCFPyL PSMA PET/CT in the BCR setting and assess the correlation between FPSAR and ¹⁸F-DCFPyL PSMA PET/CT positivity (local recurrence or distant metastases). Methods: This prospective study included 137 patients who were referred for ¹⁸F-DCFPyL PSMA PET/CT and had BCR with a total PSA of less than 1 ng/mL after radical prostatectomy (RP) (including adjuvant or salvage radiotherapy). Blood samples were collected on the day of ¹⁸F-DCFPyL PSMA PET/CT. FPSAR was categorized as less than 0.10 or as 0.10 or more. A positive ¹⁸F-DCFPyL PSMA PET/CT scan was defined by a PROMISE classification lesion score of 2 or 3, irrespective of the site of increased tracer uptake (e.g., prostate, pelvic nodes, bone, or viscera). Results: Overall, 137 blood samples of patients with BCR after RP were analyzed to calculate FPSAR. The median age at ¹⁸F-DCFPyL PSMA PET/CT was 68.6 y (interquartile range, 63.0–72.4 y), and the median PSA at ¹⁸F-DCFPyL PSMA PET/CT was 0.3 ng/mL (interquartile range, 0.3–0.6 ng/mL). Eighty-six patients (62.8%) had an FPSAR of less than 0.10, whereas 51 patients (37.2%) had an FPSAR of 0.10 or more. An FPSAR of 0.10 or more was identified as an independent predictor of a positive ¹⁸F-DCFPyL PSMA PET/CT scan, with an odds ratio of 6.99 (95% CI, 2.96–16.51; P < 0.001). Conclusion: An FPSAR of 0.10 or more after RP independently correlated with increased odds of a positive ¹⁸F-DCFPyL PSMA PET/CT scan among BCR post-RP patients. These findings may offer an inexpensive method by which to triage access to ¹⁸F-DCFPyL PSMA PET/CT in jurisdictions where availability is not replete.

在加拿大和全球范围内，获得 PSMA PET/CT 的机会有限且昂贵。对于前列腺癌治疗后生化复发 （BCR） 的患者，需要新的策略来更好地对可能从 PSMA PET 扫描中受益或可能没有获益的患者进行分层。游离与总前列腺特异性抗原 （PSA） 比值 （FPSAR） 在治疗后前列腺癌中的作用，特别是在 PSMA PET/CT 时代，仍然未知。我们在本研究中的目的是确定在 BCR 情况下转诊接受 ¹⁸F-DCFPyL PSMA PET/CT 的患者 FPSAR 的相关性，并评估 FPSAR 与 ¹⁸F-DCFPyL PSMA PET/CT 阳性（局部复发或远处转移）之间的相关性。方法：这项前瞻性研究包括 137 名患者，这些患者被转诊接受 ¹⁸次 F-DCFPyL PSMA PET/CT，并且在根治性前列腺切除术 （RP） 后 BCR 总 PSA 低于 1 ng/mL（包括辅助或挽救性放疗）。在 ¹⁸F-DCFPyL PSMA PET/CT 当天采集血样，FPSAR 分类为小于 0.10 或 0.10 或更高。阳性 ¹⁸F-DCFPyL PSMA PET/CT 扫描定义为 PROMISE 分类病变评分为 2 或 3，与示踪剂摄取增加的部位（例如，前列腺、盆腔淋巴结、骨骼或内脏）无关。结果：总体而言，分析 RP 后 BCR 患者的 137 份血样以计算 FPSAR。¹⁸F-DCFPyL PSMA PET/CT 的中位年龄为 68.6 岁（四分位距，63.0-72.4 岁），¹⁸F-DCFPyL PSMA PET/CT 的中位 PSA 为 0.3 ng/mL（四分位距，0.3-0.6 ng/mL）。86 例患者 （62.8%） 的 FPSAR 小于 0.10，而 51 例患者 （37.2%） 的 FPSAR 为 0.10 或更高。FPSAR 为 0。10 个或更多被确定为 ¹⁸F-DCFPyL PSMA PET/CT 扫描阳性的独立预测因子，比值比为 6.99 （95% CI，2.96-16.51;P < 0.001）。结论：RP 后 FPSAR 为 0.10 或更高与 BCR 后 RP 患者 ¹⁸F-DCFPyL PSMA PET/CT 扫描阳性的几率增加独立相关。这些发现可能提供了一种廉价的方法，可以在可用性不足的司法管辖区对 ¹⁸F-DCFPyL PSMA PET/CT 的可及性进行分类。