What is the typical timeline for PSA to become undetectable after radical prostatectomy?

1. What clinicians mean by "undetectable" and why the threshold matters

Laboratories and studies use different detection limits — some ultrasensitive assays detect PSA down to 0.006–0.02 ng/mL while routine cutoffs are often 0.1 or 0.05 ng/mL — so "undetectable" can mean different numeric results depending on the test used ^{[4] [3]}. Clinical decisions hinge on these thresholds because an ultrasensitive measurable PSA that is below routine cutoffs may be clinically insignificant and provoke unnecessary anxiety or intervention if misinterpreted ^{[4] [7]}.

2. Typical timeline: a practical range from weeks to a few months

Patient-facing guidance from cancer societies and major health sources converge on a short timeline: many say PSA should drop to very low or undetectable within about 4–8 weeks, often summarized as "within a couple of months" after prostate removal ^{[2] [1] [3] [8]}. Patient-education pieces and expert quotes state it "usually takes about two months" for PSA to clear from blood, and therefore recommend not testing earlier than two months ^{[4] [2]}.

3. Newer evidence: some patients take longer — median ~3–3.4 months

Cohort research and recent analyses complicate the simple two-month rule. A 2025 JAMA Oncology–centered cohort and commentary found the median time to observe an undetectable PSA was about 3.37 months and warned that assessing PSA at conventional 1.5–2.0 months can mislabel patients as having persistent PSA, leading to potentially unnecessary salvage therapy ^{[6] [5]}. CancerNetwork summarized that median times to treatment were shorter than the median time to undetectable PSA, underscoring the risk of premature intervention ^[5].

4. Why timing affects treatment decisions and overtreatment risk

Investigators and experts emphasize that checking PSA too early can cause false positives for persistent disease and prompt salvage radiation or hormonal therapy that might have been avoidable if clinicians waited for further decline ^[6]. The JAMA Oncology-linked work argues that extending the interval to at least 3 months may reduce overtreatment risk, especially in men with very high preoperative PSA where clearance can be slower ^{[6] [5]}.

5. Prognosis and longer-term context after an undetectable PSA

An initial undetectable postoperative PSA correlates with better long-term biochemical recurrence–free survival, and an undetectable value years out (for example, 5–10 years) is commonly used as a marker of surgical cure in many series ^{[7] [9]}. However, delayed detectable PSA can occur: studies describe patients who were initially undetectable and later developed measurable PSA more than six months post-op, and long-term follow-up is necessary because recurrences often appear years later ^{[10] [4] [9]}.

6. Practical takeaways for patients and clinicians

Follow-up testing schedules vary, but authoritative sources advise the first postoperative PSA no earlier than two months, with many clinicians and new research recommending waiting closer to 3 months to avoid misclassification ^{[4] [6] [5]}. Know your lab’s assay sensitivity and which numeric cutoff your team uses for "undetectable" before acting on a low-level result ^{[4] [3]}.

Limitations and open questions

Available sources describe timing ranges and differing assay definitions but do not provide a single universal cutoff or one-size-fits-all schedule; practices vary by institution and patient risk features ^{[2] [6] [4]}. Not found in current reporting: a definitive, universally accepted protocol that prescribes an exact week for first PSA testing for every patient subgroup.

Bottom line

Expect PSA to usually become very low or undetectable within about 4–12 weeks after radical prostatectomy; plan the first test at ≥2 months and consider waiting ~3 months before calling a PSA "persistent" to avoid unnecessary salvage treatment ^{[1] [2] [6] [5]}.