Radioguided sentinel lymph node dissection in patients with localised prostate carcinoma: influence of the dose of radiolabelled colloid to avoid failure of the procedure

The purpose of this study was to determine the role of the injected dose of tracer in the non-detection of pelvic sentinel lymph nodes (SLN) in patients with prostate carcinoma.

Data were evaluated from 100 patients (age range 43–77, mean 63 years). The first 72 patients (group 1) received 2 × 0.3 ml of 30 MBq-nanocolloid-99 mTc and the remaining 28 patients (group 2) received 2 × 0.3 ml of 100 MBq. Surgery consisted of the detection and dissection of lymph nodes identified as sentinel nodes, followed by an extended lymphadenectomy.

SLNs were located in the interiliac group in 54.2% of patients, in the obturator fossa in 30.7%, in the external iliac group in 10.9% and in the common iliac group in 4.2% of cases. Lymph node involvement was observed in 12% of patients. But there was a 30.6% (22/72) failure rate of the SLN procedure in group 1 and 7.1% (2/28) in group 2. An increased risk of unsuccessful SLN procedure was statistically associated with the low dose of MBq-nanocolloids (p < 0.017). Statistical correlation is also found after the exclusion of the first 30 patients from the study (learning phase of the team) (p < 0.034). None of the other parameters showed a statistical association (age, p < 0.9; Gleason score, p < 0.3; grade pT, p < 0.7). A higher grade or a greater extension of cancer inside the prostate are not responsible for the failure of the SLN procedure.

It seems necessary to inject at least 200 MBq inside the prostate to avoid a failed SLN procedure.