With the DAFE system from R. WOLF, the basic procedure is identical to that for conventional white-light endoscopy in the bronchial region. No additional preparation is necessary. In contrast to PDD (photodynamic diagnosis), no photosensitisers are necessary to generate the fluorescence.The fluorescence is produced in the body's own molecules, such as riboflavin and is therefore known as autofluorescence.

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.

Contraindications

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.

It is also possible to detect lesions about which there is still controversy as to whether they should be resected or not (for example slight dysplasia) and to monitor their development during follow up (carcinogenesis). These lesions can, when necessary, be treated early with medication or surgically if malignant growth continues.

In some situations, the detection and localisation of preinvasive lesions (stage 0 according to ISS) also allows the option of employing endobronchial therapeutic methods such as PDT (photodynamic therapy) [Mon90], [McC97], [Fre96], [Fre99] laser therapy [Cav94], cryotherapy [Oze90], therapy with electrocautery [Box98], APC (argon plasma coagulation), brachytherapy [Per97] etc.

In contrast to surgical tumour resection (for example, lobectomy, bilobectomy or even pneumonectomy), which is recommended from ISS stage I onwards [Dom00], firstly most of these procedures can generally be repeated, for example, with recurrences or new occurrences and secondly due to their less invasive character they involve no or comparatively little reduction in quality of life of the patient at least in the medium to long term in many cases. In addition to this, classical surgical resection

• is firstly not always possible: Some patients, for example, already have severely restricted lung function due to a history of smoking that would further deteriorate to an unacceptable level if the required resection was performed

• is secondly not always possible to the extent considered ideal based on the diagnosis: For example, a fifth of all patients with a radiologically occult carcinoma already have multicentric lesions [Fuj00].

If the therapy is intended to be curative, postoperative lung function must also be guaranteed.

In surgical resection, a not insignificant risk of mortality must be accepted in the order of several percent for a lobectomy [Lod98] and increasing with the extent of the resection.

A further advantage of autofluorescence endoscopy is that the margins of the tumour can be visualised clearly.

Change from white light to autofluorescence with Cursor

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