Prognostic Role of Free Psa Ratio at Biochemical Recurrence After Radical Treatments for Prostate Cancer

Prostatic specific antigen (PSA) circulates mostly in complex with protease inhibitors, but 10-30% circulates as inactive free-PSA (FPSA). In patients with prostate cancer (PCa), pretreatment FPSA is lower and used to risk-stratify patients for biopsy. However, posttreatment FPSA ratio (FPSAR) is rarely quantified, with an unexplored clinical value.

Methods The institutional database was queried to identify patients following radical prostatectomy (RP cohort) or radiotherapy (RT cohort) between 2000 and 2017. For validation, the investigators identified an independent prospective cohort with biochemical recurrence (BCR) after RP, using biobank samples (biobank cohort). All patients had at least one posttreatment FPSAR test. Kaplan-Meier (KM) method was used to compare the metastasis-free (MFS), castration-resistant PCa (CRPC)-free, and cancer-specific-survival (CSS) rates. Multivariable Cox models determined the association between posttreatment FPSAR, metastases, and CRPC.

Inclusion criteria

For the two retrospective cohorts:

• All patients that older than 18 treated for localized adenocarcinoma of the prostate between 2000 and 2017 with either radical prostatectomy or radiotherapy
• All treated patients had a rising post-treatment PSA, with at least one post-treatment free PSA blood test.

For the biobank validation cohort:

• All patients treated with radical prostatectomy for localized prostate cancer between 2000 and 2017 who had biobank samples taken when developing biochemical recurrence.

Exclusion criteria

• Patients that were younger than 18,
• Patients with prostate cancer other than adenocarcinoma, such as small cell and neuroendocrine cancer
• Patients with prostate adenocarcinoma that did not develop biochemical recurrence.
• In the retrospective cohorts - patients that did not have at least one post-treatment free PSA blood test.