Value of Narrow Band Imaging (NBI) Endoscopy in the Early Diagnosis of Laryngeal Cancer and Precancerous Lesions

Laryngeal squamous cell carcinoma (SCC) is one of the most common head and neck cancers. In many cases laryngeal SCC is diagnosed too late for curative treatment - the reasons are non-specific symptoms and very often poor social status of patients, on the other hand also limited diagnostics modalities. Its early detection and diagnosis is essential in order to maximise cure rates and to preserve vocal function. Radiological evaluation with computer tomography (CT) and magnetic resonance imaging (MRI) provides vital information on the extent of the primary tumor and the presence of cervical lymph node metastasis, but fails to identify superficial mucosal abnormalities. At present, white light laryngoscopy combined with biopsy is the standard diagnostic procedure in the assessment of laryngeal cancer and precancerous lesions. However, white light laryngoscopy provides poor quality images and has difficulty identifying epithelial changes and directly differentiating benign from malignant tumors in vivo.

The best case scenario for early detection of SCC of the upper aerodigestive tract (UADT) would be at the stage of squamous dysplasia or even carcinoma in situ. These early lesions are very difficult to detect even with multiple passes with the endoscope, if they are ≤ 1 cm in diameter. In gastroenterology are still more common used endoscopies with high magnification for detection pathological mucosal lesions, but in otorhinolaryngology is using these equipments still limited. However, in recent years are detected epithelial lesions more common by biological endoscopic methods. A well established technique, already in use for the oesophagus, is Lugol chromoendoscopy, where squamous dysplasia and carcinoma in situ appear as Lugol voiding lesions (Watanabe et al., 2003). These precancerous lesions can be easily resected via endoscopic mucosal resection, which is a minimally invasive procedure with short hospital stay. However, this technique cannot be applied in the head and neck region due to the severe mucosal irritation that may lead to severe dysphagia and even aspiration. Other biological endoscopic methods include autofluorescence, contact endoscopy or narrow band imaging.

Recently, a new high-resolution endoscopic technique, narrow band imaging, has begun to be widely used in the early diagnosis of gastrointestinal cancer. Narrow band imaging is based upon the fact that the depth of light penetration depends on the light wavelength: the longer the wavelength, the deeper the penetration. Narrow band imaging modifies the broadband white light from a xenon lamp into two narrow band illumination beams with central wavelengths of 415nm - blue light, which is designed to primarily penetrate the musoca and display superficial capillary networks, and 540 nm - green light designed to penetrate the submucosa and visualized subepithelial vessels. When these two wavelengths are used in combination, they provide and extremely high contrast image of the tissue surface. In literature (Ni et al., 2011) is described classification of intraepithelial papillary capillary loop features using narrow band imaging, which is used in diagnosis of epithelial lesions and ranging from benign to malignant. According to the literature sensitivity of NBI in detection malignant lesions (carcinoma in situ or invasive carcinoma) is 88.9%, significantly greater than that of white light visualization (68.9%), specificity of NBI is 93.2% (Ni et al., 2011).

It is possible to expect that using NBI endoscopy will be improved diagnostics early cancerous epithelial changes in hypopharynx and larynx in ENT patients with non-specific symptoms and in cases at the beginning of cancer growth, which is not detected by any other imaging methods. Also using peroperative NBI the investigators expect better detection of resection margin in cancer laser surgery and decrease of re-operations or adjuvant radiotherapy postoperatively.

Aims of project