The extent of a tumour is much easier to recognise than under white light allowing more accurate staging. This is also true when a high-resolution video bronchoscope is used instead of a conventional fibre bronchoscope in white light bronchoscopy [Fuj00]. Especially with intraepithelial lesions, this can be decisive in the choice of therapy (see above) [Ren01].

It is a great advantage of autofluorescence endoscopy – in contrast to PDD (photodynamic diagnosis) – that no medication is required to produce the fluorescence. This avoids a number of potential problems such as the approvals for the medication (known as photosensitisers), the method of administering the medication and the dose, toxicity, fading of the tumour marker, etc.

Despite great efforts in recent decades, it has not been possible to significantly improve the 5-year survival rate of patients with bronchial carcinoma which remains poor at between 10% and 15%.

One reason for this is that with conventional forms of diagnosis (including white light endoscopy), preinvasive (in other words, intraepithelial) lesions cannot be adequately detected and localised [Ken01]. However, it can be assumed that a more or less high proportion of these precancerous lesions will develop into invasive carcinomas. This proportion is considerable with carcinoma in situ [Ven00] but cannot be ignored in cases of medium to severe dysplasia [Ris88].

Especially with the preinvasive lesions (stage 0 according to ISS) the chances of healing with a 5-year survival rate of over 90% must be considered good but diminish dramatically as the disease develops [Tho02].

The reason for the low sensitivity of conventional forms of diagnosis for intraepithelial lesions, on the one hand, is the small size of these lesions which are usually only a few millimetres in diameter (at times even less) and often extend over only a few cell layers [Lam00]. As a result, they cannot always be distinguished from surrounding healthy tissue by their form; in other words by their size and elevation.

On the other hand, differentiation between preinvasive lesions and healthy tissue based on colour is very restricted or even impossible.
As a result, for example, only approximately 30% of existing carcinomas in situ could previously be made visible 30% [Woo83]. With dysplasia, an even smaller proportion must be assumed due to the small dimensions and less conspicuous appearance.

Autofluorescence endoscopy is a great help in dealing with this problem. It leads to a significant improvement in the detection and localisation of intraepithelial lesions [Gou], [Ren01], [Hor99].

By exciting bronchial tissue by exposing it to violet and blue light at a defined wavelength, autofluorescence light is induced in the endogenous fluorophors of the bronchial walls. This radiation is in a waveband lower than that of the applied excitation light. The fluorescent response depends greatly on the state of the tissue (healthy tissue fluoresces strongly, whereas the fluorescence of pathological tissue is weaker) so that it is possible to distinguish early stage cancer and precancerous tissue clearly from healthy tissue, in contrast to conventional white light endoscopy [Zel].

Even tissue with only slight pathological changes stands out clearly from healthy tissue in the fluorescence image.

All patients with suspected preinvasive lesions or microinvasive carcinoma should therefore be examined by fluorescence bronchoscopy.

These include:

• Patients with known or previously diagnosed lung cancer
• Patients with lung cancer suspected on the basis of direct symptoms such as haemoptysis, dry cough, chronic or recurrent pneumonia, progressive dyspnoea, etc.
• Patients with lung cancer suspected on the basis of diagnostic symptoms such as positive sputum cytology, increased tumour marker concentration, X-ray findings, etc.
• Patients with suspected lung cancer due to their anamnesis 

When collecting the anamnesis, the following aspects should be taken into account:

• Inhalation smoking, possibly also in conjunction with alcohol abuse
• occupational influences (exposure to certain hard metals, aromatic hydrocarbons and ionising radiation)
• predisposing disease (for example tuberculosis)
• recurrence of a treated pulmonary tumour
• pulmonary metastasis of an extrapulmonary tumour (possibly already treated)
• formation of secondary tumours as a sequel to radiation or cytostatic therapy of another tumour 

For autofluorescence endoscopy, the endoscopically accessible bronchial regions and therefore central carcinomas and early forms are of significance.

Patients who should be excluded from fluorescence bronchoscopic examination are primarily those barred from conventional white light endoscopy.

Also patients

• who have received photosensitising substances in the preceding three months
• who have been treated with cytostatic drugs or radiologically in the preceding three months
• who have been treated chemoprophylactically in the preceding three months.

The extent of a tumour is much easier to recognise than under white light allowing more accurate staging. This is also true when a high-resolution video bronchoscope is used instead of a conventional fibre bronchoscope in white light bronchoscopy [Fuj00]. Especially with intraepithelial lesions, this can be decisive in the choice of therapy (see above) [Ren01].

It is a great advantage of autofluorescence endoscopy – in contrast to PDD (photodynamic diagnosis) – that no medication is required to produce the fluorescence. This avoids a number of potential problems such as the approvals for the medication (known as photosensitisers), the method of administering the medication and the dose, toxicity, fading of the tumour marker, etc.