Autofluorescence spectroscopy for the classification of oral lesions

Oral cancer is a disease that occurs in approximately 800 new patients in the Netherlands each year. Most of these patients have a history of heavy smoking, often in combination with the frequent use of alcoholic drinks, especially strong liquors. More than 90% of these cancer patients suffer from oral squamous cell carcinomas which arise from the upper layer of the tissue: the oral mucosa. It is this mucosa that has been exposed to tobacco and alcohol, and is therefore at risk for developing premalignant lesions and invasive tumours. During the process of so-called ‘field cancerization’, multiple areas of the oral mucosa undergo carcinogenic changes. This is an important feature of oral carcinogenesis and it can explain why the occurrence of second primary tumours in patients is so often seen. In fact, 28% of the patients diagnosed with a squamous cell carcinoma (SCC) of the oral mucosa will develop a second primary tumour within ten years. As with all cancers, the prospects for the patient are better when the malignancy is found in an early stage. Treatment of small tumours, without regional metastases, give higher survival rates, better functional and esthetic results and a lower morbidity than in the case of advanced tumours. Early treatment strongly improves the survival rates and results in a lower morbidity. For example, a premalignant lesion can be removed by CO2 laser evaporation of the affected epithelium (a mildly invasive treatment), while advanced squamous cell carcinoma’s generally require extensive surgery and/or radiotherapy which may profoundly affect certain essential functions like swallowing and speech. Furthermore, these advanced carcinomas can metastasise, which significantly reduces the survival chances. For this reason, patients who are at high risk for developing oral cancer, i.e. patients that have been treated for oral cancer, are submitted to a strict screening protocol by a specialized oral and maxillofacial surgeon (oral oncologist). Upon discovery of a lesion of the oral mucosa by visual inspection, it is impossible to classify the lesions as harmless or potentially malignant. Most premalignant lesions present as whitish (leukoplakia) or reddish (erythroplakia) lesions and usually resemble some far more common benign lesions, even to the experienced eye. Only a biopsy can provide the final diagnosis. Unfortunately, the number of biopsies that can be obtained within one session is usually limited due to the complex anatomy of the head and neck region. Furthermore, the biopsy can result in some discomfort for the patient and of course the pathological examination costs time and money. Another important drawback is that the biopsy results are not always representative for the complete lesion. An oral lesion can contain local premalignant changes at one position, while it can still be benign at a position only a few millimetres away. This can result in underdiagnosis, or the need for repeated biopsies if the oral oncologist is not convinced that a lesion is benign.