Size of lymph-node metastases in prostate cancer patients undergoing radical prostatectomy: implication for imaging and oncologic follow-up of 2705 lymph-node positive patients

Background Despite modern imaging modalities, lymph-node staging before radical prostatectomy (RP) remains challenging in patients with prostate cancer (PCa).

The visibility of lymph-node metastases (LNMs) is critically influenced by their size.

Objective This study aims to describe the distribution of maximal tumor diameters (i.e., size) in LNMs of pN1-PCa at RP and its consequences on visibility in preoperative imaging and oncological outcomes.

Design, setting, and participants A total of 2705 consecutive patients with pN1-PCa at RP, harboring a cumulative 7510 LNMs, were analyzed.

Descriptive and multivariable analyses addressed the risk of micrometastases (MM)-only disease and the visibility of LNMs.

Kaplan–Meier curves and Cox analyses were used for biochemical recurrence-free survival (BCRFS) stratified for MM-only disease.

Results The median LNM size was 4.5mm (interquartile range (IQR): 2.0–9.0 mm).

Of 7510 LNMs, 1966 (26%) were MM (≤ 2mm).

On preoperative imaging, 526 patients (19%) showed suspicious findings (PSMA-PET/CT: 169/344, 49%).

In multivariable analysis, prostate-specific antigen (PSA) (OR 0.98), age (OR 1.01), a Gleason score greater than 7 at biopsy (OR 0.73), percentage of positive cores at biopsy (OR 0.36), and neoadjuvant treatment (OR 0.51) emerged as independent predictors for less MM-only disease (p < 0.05).

Patients with MM-only disease compared to those harboring larger LNMs had a longer BCRFS (median 60 versus 29 months, p < 0.0001).

Conclusion Overall, 26% of LNMs were MM (≤ 2mm).

Adverse clinical parameters were inversely associated with MM at RP.

Consequently, PSMA-PET/CT did not detect a substantial proportion of LNMs.

LNM size and count are relevant for prognosis.