Sentinel lymph node dissection combined with meticulous histology increases the detection rate of nodal metastases in prostate cancer.

PURPOSE: To evaluate benefits of sentinel lymph node (SLN) biopsy for staging accuracy in prostate cancer. Extended pelvic lymph node dissection (ePLND) is a preferred staging tool; however, it may underestimate the incidence of nodal involvement.

METHODS

Eighty patients with estimated risk of lymphadenopathy above 5 % based on Briganti nomogram had Tc-99m-labeled nanocolloid injected into the prostate. Planar lymphoscintigraphy and single-photon emission computed tomography/CT were performed to localize SLNs. Radioguided SLN dissection was followed by backup ePLND comprising external iliac, obturator and internal iliac regions. All SLNs were serially sectioned every 150 μm and examined using hematoxylin and eosin; immunohistochemical staining was applied every 300 μm.

RESULTS

A total of 335 SLNs were detected, and 17 % were located outside ePLND template. Nodal metastases were diagnosed in 32 patients (40 %). Without radioguided SLN localization, solitary metastases posteriorly to the branches of the internal ilaic vessels, in pararectal and common iliac regions would not have been removed in five of 32 patients (16 %). Using standard histology protocol, we would have diagnosed metastases in 23 patients with median size of 2.8 mm. Serial sectioning of SLN and immunohistochemistry led to the detection of metastases in additional nine patients (28 %) with median size of 0.2 mm.

CONCLUSION

ePLND comprised 83 % of SLNs, at least one SLN laid outside its template in 28 % of patients. ePLND and SLN dissection combined with nodal serial sectioning and immunohistochemistry increased the detection rate of nodal metastases by 68 % in comparison with ePLND alone and standard histology protocol.