Oral cancer starts in the mucosa of the mouth and the most common site is the tongue and gingiva. One of the most important issues for the prognosis is to surgically remove all the cancer, at the sides as well as at the deep margin. To accomplish that, it is crucial to identify the border between tumour and healthy tissue. Traditionally white light from a head light or operation theatre lamp is used to illuminate the area of the tumour. Narrow Band Imaging (NBI) is an optical technique where ordinary white light is filtered so only the blue light in it is used. Illuminating the mucosa with this blue light through an endoscope with high definition image, makes the blood vessels appear more clearly. The altered blood vessels that the cancer produce can thereby be seen and mark the area where the tumour starts.

This study examines if NBI is helpful in the decision of where the border between the cancer and the normal mucosa is. If so, NBI might improve the possibility to remove all cancer tissue compared to using the ordinary white light.

This study will also increase the knowledge about the NBI technique, which is helpful in the examination of patients with suspected head and neck cancers and at the follow-up of patients after treatment.

Participants are patients with oral cancer presenting at the otorhinolaryngology department in Örebro University hospital in Sweden for surgical treatment. The surgery will be done in the usual fashion but the mucosa surrounding the tumour will also be illuminated by NBI and this picture of the vessels will be compared to the microscopic analysis by the pathologist, the so called PAD. Thereby we seek to compare the border in white light to the border seen with NBI.

Patients with primary oral cavity cancer will be examined with Narrow Band Imaging (NBI) at the time of surgery. Olympus® equipment will be used together with straight 5,9 mm endoscopes.

First the tumour border seen in white light will be defined. Thereafter endoscopic examination with white light and NBI will be performed and recorded. Then the tumour border seen in white light will be marked with dots by monopolar diathermy. Finally the area is examined again with NBI and if the tumour border is seen outside the border seen in white light, that area is marked by a suture for the pathology report.

Since the purpose of this study is to gain knowledge of NBI in oral cavity cancer, the resection margin will be marked at least 10mm from the tumour border as it is seen in white light in the ordinary fashion. However there are evolving evidence that NBI better delineate tumour border in larynx and some data for the oral cavity, therefore any suspected mucosa according to NBI outside the ordinary resection margin will be included with a small margin.

There is no uniform definition of the NBI pattern in oral cavity cancer. The planned criteria is changed IPCL type III/IV according to Takano (see ref.) and so called "marked brown dots" as criteria for precancerous or cancerous mucosa according to NBI.

The tumour border in white light and NBI will be compared and PAD is considered gold standard.

To reach 80% power with 5 % type 1 error, two-sided test, and 25% of the examinations anticipated to show different tumour border with NBI, 49 participants will be needed.

Inclusion Criteria:

Biopsy proven squamous cell carcinomaI. International Statistical Classification of Diseases and Related Health Problems (ICD) 10 C02-C06.

Exclusion Criteria:

• former extensive surgery in the oral cavity that effects the examination
• former radiation to the oral cavity
• patients not suitable for surgery

The study population will be patients with oral cancer presenting for treatment at our clinic. All patients that meet the eligibility criteria will be asked to participate.

Pseudonymised data of the NBI-picture in relation to PAD will be shared.

6 months after publication

Coded, computerized IPD will be available upon a request with the serious intention to improve the scientific knowledge and transparency.