Introduction

Determining the risk of disease recurrence after radical prostatectomy (RP) is useful in early risk stratification. PSA nadir after RP is a strong predictor of biochemical recurrence (BCR). However, the time to nadir (TTN) has not been studied in the post-RP setting. We analyzed the association between PSA nadir level and TTN with BCR risk after RP among patients in the Shared Equal Access Research Cancer Hospital (SEARCH) Database.

Methods

Using SEARCH, we identified men who either had an undetectable PSA (0 ng/ml) within 1-3 months after RP, or a detectable PSA within 1-3 months after RP and a follow-up PSA within 3-6 months after RP (n=1882). Men with a BCR or secondary treatment within 6 months of RP were excluded. Nadir was the lowest PSA within 1-6 months. We divided patients into 4 nadir groups: undetectable nadir and TTN 3-6 months (n=139), undetectable nadir and TTN 1-2.9 months (n=1290), detectable nadir and TTN 3-6 months (n=146), and detectable nadir and TTN 1-2.9 months (n=307). A Cox model was used to test the association between nadir group and risk of BCR. Time zero for all groups was 6 months after RP. The model was adjusted for race, BMI, age, year, surgical center, pre-RP PSA, Gleason score, and pathological features.

Results

During a median follow-up of 65 months (IQR 29-111), 480/1882 (26%) men had a BCR. Among men with an undetectable PSA nadir and TTN 3-6 months, median time to first PSA was 1.6 months (IQR 1.3-2.1 months) after RP and median initial PSA was 0.02 (IQR 0.01-0.03). Among men with a detectable PSA at 1-3 months, 48% had a lower follow-up PSA 3-6 months after RP which was undetectable in 23% and lower but still detectable in 25%. Men with an undetectable PSA nadir and TTN 1-2.9 months had similar risk of BCR to men with an undetectable PSA nadir and TTN 3-6 months (HR 0.90, p=0.63). However, those with detectable nadir had increased risk of BCR (TTN 3-6 months: HR 2.01, p=0.009; TTN 1-2.99 months: HR 3.83, p<0.001), and those with shorter TTN (1-2.99 months) had higher risk of BCR than men with longer TTN (3-6 months) (p<0.001).

Conclusions

Among men undergoing RP with an undetectable PSA nadir, there was no association between TTN and risk of BCR. However, a shorter TTN was associated with an increased risk of BCR in men with detectable nadir. Intriguingly, nearly half of the men with a detectable PSA in first 3 months after RP had a lower follow-up PSA between 3 and 6 months after RP. This is contrary to common thinking that the first PSA after surgery is the nadir.

Funding

none