Does PSA Nadir + 2 ng/mL Always Indicate Biochemical Recurrence? A PSA Kinetics-Based Evaluation Following Carbon Ion...

Area of Science:

• Oncology
• Radiation Oncology
• Urology

Background:

• Biochemical recurrence in prostate cancer post-radiotherapy is often defined by the Phoenix criteria (PSA nadir + 2 ng/mL).
• PSA bounce, a transient PSA elevation without clinical recurrence, can complicate the interpretation of the Phoenix criteria.
• High-risk prostate cancer (HR-PCa) requires precise monitoring for treatment effectiveness and recurrence detection.

Purpose of the Study:

• To evaluate prostate-specific antigen (PSA) kinetics following scanning-method carbon ion radiotherapy (CIRT) in HR-PCa patients.
• To assess the clinical validity and limitations of the Phoenix criteria in the context of CIRT for HR-PCa.
• To differentiate between true recurrence and PSA bounce after CIRT.

Main Methods:

• Retrospective analysis of 171 HR-PCa patients treated with CIRT and androgen deprivation therapy.
• Classification of patients into non-recurrence, pseudo-recurrence (PSA > 2 ng/mL with spontaneous decline), and recurrence groups.
• Kaplan-Meier and ROC analyses to determine biochemical relapse-free survival and optimal PSA cutoffs.

Main Results:

• 10.5% of patients met the Phoenix criteria (PSA > 2 ng/mL), with 33.3% of these experiencing spontaneous PSA decline (pseudo-recurrence).
• PSA bounce was observed in 33.9% of patients.
• ROC analysis suggested an optimal PSA cutoff of 1.91 ng/mL, with the 2 ng/mL cutoff showing a low positive predictive value (61.1%) due to PSA bounce.

Conclusions:

• A PSA rise above 2 ng/mL after CIRT for HR-PCa does not definitively indicate recurrence.
• The Phoenix criteria may lead to overdiagnosis of recurrence due to PSA bounce.
• Careful interpretation of PSA kinetics is crucial to avoid overtreatment in HR-PCa patients post-CIRT.