Therapeutic applications

Compared to surgery, radiotherapy and chemotherapy, PDT can appear miraculous. It nevertheless only allows small sized and easily accessible tumours to be treated, for example skin, bladder, oesophagus, lung, stomach or cervical tumours. For cancers which are at a more advanced stage or which are more difficult to reach, PDT can be used as a supplement to classic protocols, particularly if the latter prove to be insufficiently effective or provoke resistance. ‘There are currently effective treatments for numerous cancers. Nevertheless certain amongst them have to be abandoned because the tumours become resistant to chemotherapy or to radiotherapy, for example. One of the major advantages of PDT is that it does not induce any resistance. It allows the volume of the tumour to be reduced and the patient’s vital prognosis to be improved,’ points out Jacques Piette.

PDT can also be used to diagnose tumours, a procedure named ‘photodiagnosis.’ Excited by blue light, the PS emits red fluorescence, which enables not only tumours to be located with great precision but also enables surgeons to be guided during tumour ablation (fluorescent guided resection). ‘Oncology surgeons use PDT to locate the tumour and remove a maximum of sick tissues. If there are still fluorescent cells left after surgery they change their wavelength (from blue to red) and increase the power of the laser beam to eradicate the remaining tumoral cells by photodynamic therapy and thereby obtain an improvement of the effects of dissecting the tumour only,’ describes the researcher.

Despite these very encouraging results and the numerous research projects which are still underway, PDT is still under used, apart from in dermatology (certain skin tumours), for bladder tumours or to help in diagnosing brain tumours.  Several centres, in England, Germany and France for example use PDT in a repeated manner in the case of tumours which are multi-resistant to classic forms of treatment. No-one doubts that it is just a question of time; more and more university and hospital centres are becoming interested in photodynamic therapy. Recently,PDT has also demonstrated its effectiveness in the fight against bacterial infections which are multiresistant to antibiotics.