Retroperitoneal and lateral pelvic lymphadenectomy mapped by lymphoscintigraphy for rectal adenocarcinoma staging

The good prognosis of retroperitoneal and lateral pelvic lymphadenectomy has raised the question of whether total mesorectal excision is suitable for adequate staging of rectal adenocarcinoma patients. The aims of this study were to determine the accuracy of dye and probe detection of metastatic retroperitoneal and/or lateral pelvic nodes and to define the upstaging impact of retroperitoneal and lateral pelvic lymphadenectomy in rectal adenocarcinoma patients.

Ninety-seven rectal adenocarcinoma patients were submitted to total mesorectal excision and retroperitoneal and lateral pelvic lymphadenectomy. Lymphoscintigraphy using technetium-99 m-phytate and patent blue was performed to detect blue and/or radioactive retroperitoneal and/or lateral pelvic nodes which were examined histopathologically and immunohistochemically with a step-sectioning technique.

Mesorectal mean node count was 11.5 and retroperitoneal and/or lateral pelvic node was 11.7. Retroperitoneal and lateral pelvic lymphadenectomy identified metastases in 17.5%, upstaging 8.2%. Variables related to metastatic retroperitoneal and/or lateral pelvic nodes were the following: Stage III in total mesorectal excision specimens (P < 0.04), pT3/pT4 tumors (P = 0.047), high levels of carcinoembryonic antigen (P = 0.014) and large tumors (P = 0.03). Marker migration to retroperitoneal and/or lateral pelvic nodes occurred in 37.1%, upstaging 11.1%. The markers' accuracy in the detection of metastatic retroperitoneal and/or lateral pelvic nodes was 100%.

Retroperitoneal and lateral pelvic lymphadenectomy detected an important rate of metastatic retroperitoneal and/or lateral pelvic nodes (RLPN), resulting in upstaging. When markers migrated, they were able to detect RLPN metastases. The use of markers should be improved in the identification of RLPN metastases for selective indication of retroperitoneal and lateral pelvic lymphadenectomy.