Sentinel lymph node biopsy for head and neck mucosal cancers - an update on the current evidence

Diagnostic value of indocyanine green for sentinel lymph node mapping and lymph node metastasis in oral/oropharyngeal carcinoma

Indocyanine green (ICG) fluorescence-based sentinel lymph node (SLN) biopsy has been promoted to detect early metastasis of oral/oropharyngeal carcinoma, but its diagnostic value still remains unclear. In this letter, we identified 6 studies on ICG fluorescence based SLN in the detection of lymph node metastasis in oral/oropharyngeal carcinoma. For detection of metastatic lymph node, the overall sensitivity and specificity of the studies were 0.86 and 0.91, respectively. SROC curve was determined according to the combined sensitivity and specificity, and the overall area under the curve AUC was 0.93. On the whole, ICG fluorescence-based SLN biopsy showed promising effect for earlier detection and staging.

Comparative study on the diagnostic value of intravenous/peritumoral injection of indocyanine green for metastatic lymph node location in patients with head and neck squamous cell carcinoma (HNSCC)

Background

Accurate assessment of regional lymph node (LN) status is essential for the treatment of head and neck squamous cell carcinoma (HNSCC) patients. In this study, we aimed to compare the difference between intravenous injection of indocyanine green (ICG) and peritumoral injection of ICG in the location of metastatic LNs.

Methods

Twenty-nine patients were enrolled in this study with 13 patients receiving intravenous injection of ICG and 16 patients receiving peritumoral injection of ICG. During the surgery, the fluorescence-positive LNs in vivo were sent to undergo frozen section after fluorescence intensity was recorded. After the cervical LN dissection, all LNs were sorted by region, and the fluorescence intensity was recorded before the LNs were sent for paraffin section.

Results

During the surgery, both intravenous or peritumoral injections with near-infrared (NIR) fluorescence imaging of ICG had their respective pros and cons in vivo, with the sensitivity and specificity being 62.5%/75% and 98.1%/89.1% respectively. After the surgery, both methods could reduce the pathological workload by preselecting the LNs at-risk in the premise of accurate assessing the cervical LN stage. However, intravenous ICG administration was more valuable in determining all types of LN status according to the fluorescence intensity [area under the curve (AUC): 0.91 vs. 0.78, P<0.001].

Conclusions

With the assistance of NIR fluorescence imaging using ICG, both administration methods could reduce the postoperative complication and the pathological workload, whereas the intravenous mode of ICG administration is superior in application value.

Efficient fluorescence detection of protoporphyrin IX in metastatic lymph nodes of murine colorectal cancer stained with indigo carmine

Protoporphyrin IX (PpIX), a biochemical converted from 5-aminolevulinc acid (5-ALA) in living cells, is useful for intraoperative fluorescent detection of cancer metastasis in lymph nodes (LNs). However, unknown is whether the fluorescence of PpIX can be detected in the LNs when they coexist with indigo carmine, a blue dye commonly used for identification of sentinel LNs during surgery. To address this issue, we sought to evaluate the diagnostic usefulness of PpIX fluorescence in the presence of indigo carmine in a mouse LN metastasis model of rectal cancer after administration of 5-ALA. Spectral analysis of pure chemicals revealed that the absorption spectrum of indigo carmine widely overlapped with the fluorescence spectrum of PpIX specifically at the peak of 632nm, a common emission wavelength for detecting PpIX, but not at the other peak of 700nm. Due to such spectral overlap, the PpIX fluorescence intensity was significantly attenuated by mixture with indigo carmine at 632nm, but not at 700nm. Accordingly, fluorescent measurements of the mouse metastatic LN revealed more intense presentation of PpIX at 700nm than at 632nm, indicating that the diagnostic usefulness is greater at 700nm than at 632nm for the indigo carmine-dyed LNs after administration of 5-ALA. From these observations, we propose that the fluorescence measurement is more efficient at 700nm than at 632nm for detection of PpIX in metastatic LNs stained with indigo carmine.

An update on the latest evidence for managing the clinically negative neck (cN0) in oral squamous cell carcinoma

The single most important prognostic indicator for survival in oral squamous cell carcinoma (OSCC) is the presence of lymph node metastases in the neck. While the treatment of the clinically node positive (cN+) neck is well established, the management of the clinically negative neck (cN0) is controversial. Various strategies have been advocated including close observation including regular ultrasound imaging, elective neck dissection and sentinel lymph node biopsy. Neck dissection surgery is not without potential morbidity with shoulder dysfunction being the main complication. A number of factors are associated with increased risk of neck node metastasis including primary tumour thickness and peri-neural invasion. A recent prospective randomised trial has found survival benefit following neck dissection even in patients with a cN0 neck at presentation. We discuss the latest evidence for managing the cN0 in OSCC and include our own experience on the role of neck dissection in certain cases.