Background: Historically, retropharyngeal node has been considered to be the first echelon node in case of oropharyngeal carcinoma. Given the impetus on minimally invasive treatment in the form of transoral surgery and conventional neck dissection for early stage oropharyngeal malignancy, there remains a possibility of undertreatment if retropharyngeal lymph node status is not adequately assessed.
- To identify sentinel lymph node in carcinoma tonsil by SPECT-CT, intraoperative gamma probe and histology.
- To identify the incidence of retropharyngeal lymph node positivity.
Design: Prospective cohort study
Setting: Tertiary care centre
Participants: Patients with carcinoma tonsil T1-T3, N0 planned for upfront surgery
Intervention: Patients underwent peritumoural injection of filtered (0.22 micron filter) Tc-99 sulphur colloid (4 to 5 mCi) followed by SPECT-CT to identify the level of the brightest hot spot corresponding to the first echelon node. During conventional neck dissection, hand held gamma probe was used to identify the sentinel node (highest 10 second count). Retropharyngeal lymph node was sampled in all patients. All lymph nodal levels were sampled separately and subjected to serial sectioning.
Results: This study has been performed on 13 cases of carcinoma tonsil (T1-1, T2-7, T3-5). Primary tumour was addressed by TORS (n-7), TOUSS (n-5) and paramedian mandibulotomy (n-1). Retropharyngeal node sampling was by the transcervical route in 10 patients and by TORS in 3 cases. Frequency of sentinel node identification by SPECT-CT was as follows: Ipsilateral level 2a- 9/13, Ipsilateral level 2b-1/13, Ipsilateral level 3-1/13, Contralateral retropharyngeal node- 1/13, bilateral level 2a- 1/13. Frequency of sentinel node identification by hand held gamma probe was as follows: Ipsilateral level 2a-11/13, Ipsilateral level 3- 1/13, no uptake-1/13. Positive occult nodes were seen in 7/13 (53.84%) patients (T2-3, T3-4). Corresponding lymph nodal levels were: ipsilateral level 2a- 6/7, ipsilateral level 2b- 2/7, ipsilateral level 3-1/7 (1 patient had involvement on multiple nodal levels). Average number of sentinel nodes identified per patient was 4.23 (2-9). Retropharyngeal node was demonstrated on SPECT-CT in 1 patient (Contralateral) and by hand-held gamma probe in 1. Histologically, lymph nodal tissue was identified in only one patient (non-metastatic). Sensitivity of SPECT-CT, intraoperative gamma probe and combined use of SPECT-CT and hand-held gamma probe was: 83.3%, 100% and 100%, respectively. Corresponding specificities were 50%,20% and 50%, respectively.
Conclusion: Occult metastasis rate of 53.84% in N0 carcinoma tonsil patients warrants elective neck treatment even in limited local disease. To the best of our knowledge this is the largest series where retropharyngeal lymph node status has been investigated in a homogenous data set of N0 carcinoma tonsil and we have so far not encountered histopathological or SPECT-CT evidence of metastasis to retropharyngeal nodes. Due to encouraging results obtained with combined use of SPECT-CT and hand held gamma probe, this modality can be used as an alternative to conventional selective neck dissection by limiting nodal sampling to superselective neck dissection.