Should we redefine the Phoenix criteria for biochemical recurrence after primary radiotherapy?

The Phoenix criteria, which define biochemical recurrence (BCR) after radiotherapy as a prostate specific antigen (PSA) rise of at least 2 ng/ml above nadir, were developed to improve consistency in outcome reporting and distinguish genuine cancer recurrence from transient, noncancerous PSA fluctuations, commonly referred to as PSA "bounces". However, in the current era of advanced imaging and precision oncology, this definition is increasingly viewed as inadequate. This review critically examines recent evidence challenging the clinical utility of the Phoenix definition and explores potential alternatives that better reflect disease biology and patient outcomes.

Modern imaging techniques, particularly prostate-specific membrane antigen (PSMA) PET/computed tomography (CT), have demonstrated the ability to detect recurrent prostate cancer at PSA levels well below the Phoenix threshold, allowing for earlier salvage interventions. Additionally, PSA kinetics such as nadir levels and doubling time provide superior prognostic information compared to static PSA thresholds. Multiparametric risk models that also incorporate PSMA PET/CT findings, PSA kinetics and clinical features may enable more accurate stratification of patients into low-risk and high-risk BCR categories. This evolving approach supports the notion that early, risk-adapted treatment can improve outcomes in high-risk patients, while reducing overtreatment in those at low risk.

The Phoenix criteria no longer align with the capabilities of current diagnostic and prognostic tools. Redefining BCR using dynamic PSA metrics and advanced imaging could facilitate timely salvage treatment in patients at a high risk and allow surveillance strategies in those unlikely to progress. Prospective validation is warranted to inform future clinical guidelines.