The Diagnostic Role of Radioactivity in Sentinel Nodes in Oral and Oropharyngeal Cancer

Sentinel lymph node biopsy (SNB), using radioactive tracers, is a novel, interesting tool in the staging of patients with oral and oropharyngeal squamous-cell carcinoma (OOSCC), which could lead to a reduced rate of elective neck dissections. The aim of the study was to evaluate the ranking of measured radioactivity in the sentinel lymph nodes (SLNs) and to correlate these findings with histopathological results to assess the number of SLN being sufficient for exact staging of the neck. In 77 consecutive patients with T1–4 OOSCC clinically and positron emission tomography–staged N0, between 15 and 55 MBq of Tc- 99m-labeled albumin-microcolloids were injected peritumorally and 213 SLNs were excised by small skin incisions using a gamma probe 2–3 hours later. The counts per second (cps) were measured ex vivo and excised SLNs were ranked according to their cps defining the LN with the highest activity as primary SLN, followed by a 2nd, 3rd, and so forth, SLN. Elective neck dissections were not performed. Median activity was 213 cps. All levels harbored SLNs with a maximum (43%) in level II and a minimum in level V(1%). SLNs in level II had significantly higher tracer accumulation (median, 289 cps) than those in levels I (144 cps) and IV (149 cps), but distant levels did not have significantly lower counts, compared to proximal. Eight (8) pathologically positive SLNs in 7 patients (7/77 = 9%; median activity, 157 cps) were detected. The median counts of the positive SLNs were not significantly different from those of the 205 negative SLNs (235 cps). The positive SLN was the one with the highest tracer accumulation in 4 cases, with the second highest in 1 case, and with the third highest tracer accumulation in 2 cases. Three (3) positive SLN were in level IB, 4 in level IIA, and 1 in level III. One (1) patient had 2 positive SLNs: a SLN with the third highest activity in level IIB and a SLN with the fifth highest activity in level III. In OOSCC, excision of only 1 SLN is not feasible. The positive SLNs were not necessarily the hottest nodes. Utilizing radiotracer lymphatic mapping, the 3 SLNs with the highest activity should be excised for exact staging of the neck in patients with T1–3 tumors. Excision of all radioactive nodes is recommended until further studies will prove this result. Large T4a tumors should not be staged using SNB.