Use of the gamma probe in sentinel lymph node biopsy in patients with prostate cancer

To describe the reproducibility of the sentinel lymph node technique in patients with prostate cancer and verify if there is improved accuracy over modified lymphadenectomy.

Twenty-three patients with biopsy proven prostate cancer were enrolled in this study. Lymphoscintigraphy was performed after the transrectal administration of Tc sulfur colloid guided by ultrasound, with one injection in each prostate lobe. Images were obtained 15 and 180 min after injection. Sentinel lymph node was harvested during surgery using a gamma probe, followed by extended lymphadenectomy.

The mean age of the patients in this study was 66 years. An average of 3.36 sentinel lymph nodes was found for each patient. Radioactive lymph nodes were identified by the gamma probe in 21 out of 23 patients. In one of the patients there was no radiopharmaceutical migration from the injection site and in another the sentinel lymph node was visualized by lymphoscintigraphy but was not found during surgery. Three patients had lymph node metastasis; in one of these patients the sentinel lymph node was the only positive node and was found outside the modified lymphadenectomy region (obturator fossa and the external iliac).

Sentinel lymph node biopsy in prostate cancer adds important information to the staging of patients, not always attained through the lymphadenectomy restricted to the obturator fossa and external iliac. Such information is essential for the choice of the best treatment to be applied.