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

INTRODUCTION: 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. METHODS: Data were evaluated from 100 patients (age range 43-77, mean 63 years). The first 72 patients (group 1) received 2 x 0.3 ml of 30 MBq-nanocolloid-99 mTc and the remaining 28 patients (group 2) received 2 x 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. RESULTS: 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. CONCLUSION: It seems necessary to inject at least 200 MBq inside the prostate to avoid a failed SLN procedure.