@beaquilter
I actually collected a bunch more information about this today.

The threshold for an undetectable PSA level is not universally standardized. The American Urological Association (AUA) and the European Association of Urology (EAU) generally define undetectable PSA as below 0.1 ng/mL post-prostatectomy. However, with ultrasensitive tests, some clinicians consider values below 0.03 ng/mL as more indicative of remission. This has sparked debate over whether lower detection limits provide meaningful insights or cause unnecessary anxiety due to minor fluctuations.

A study in The Journal of Urology found that many patients with ultrasensitive PSA levels between 0.03 and 0.05 ng/mL remained stable for years without progression. However, those with steadily rising PSA levels, even within this range, were more likely to experience biochemical recurrence, typically defined as a confirmed increase to 0.2 ng/mL or higher. This suggests that while an isolated reading of 0.04 ng/mL is not necessarily concerning, its trajectory is key in guiding clinical decisions.

The significance of 0.04 ng/mL also depends on treatment considerations. Some oncologists use ultrasensitive PSA levels to determine the timing of additional interventions like radiation therapy. Research in European Urology indicates that initiating salvage radiotherapy when PSA is below 0.1 ng/mL improves long-term outcomes. However, distinguishing between transient PSA elevations and meaningful recurrence is challenging, as unnecessary treatment can lead to side effects like urinary incontinence and bowel dysfunction.