Abstract
Aim of this study was to investigate
some possibilities of Photodynamic Therapy (PDT) as an alternative treatment to
current treatment strategies for benign lesions of the mouth.
That regards recurrent benign aphthosis (RBA) as well as ?white? lesions of the
mouth e.g leukoplakia and oral lichen planus. Both of these ?white? lesions
present a tendency to a malignant transformation. All the current therapeutic
methods represent a high recurrency rate and most of them side effects.
Aphthosis is a painful disease and only symptomatic therapy is generally
applied. Therefore search for an alternative treatment method is mandatory.
The use of (PDT) for the curative treatment of superficial tumors
of the skin and for the palliative treatment of disseminated tumors of the skin
and the oral mucosa is well known. PDT is based on a photochemical process,
where Photosenbilisators (PS) act cytotoxic by generation of 1O2
after laser irradiation. For the clinical use of PDT the abnormal tissues
selectively should absorb these substances that after systemical or local
application after irradiation with a certain light dose, the tissues will be
destroyed and simlultaneously the normal tissues should be maintained.
Toluidine blue-O and Methylenblue(MB) have proven both, antibacterial and photodynamic activity (potency to
generate 1O2). These substances are already used for the
detection of malignant changes of the mucosa by topical application. These
substances were studied regarding their photostability (change of their
absorption after irradiation, Photobleaching) and their penetration into the
oral mucosa. In the clinical investigation both substances we applied to
patients with leukoplakias, oral lichen planus and recurrent benign aphthosis.
Photosensibilisation was achieved with MB, TB-O, ALA, a topical precursor of
PPIX, well known in superficial topical PDT.
The results of the spectralphotometric
studies for TB-O and MB with and without irradiation showed a linear decline of
the Extinktion of TB-O and MB with increase of the applied Energy. The
penetration studies on normal mucosa showed that a visible penetration of MB
and TB-O was restricted to the 1-2 first cell layers. The penetrationdepth for
MB and TB-O was higher for Condylomata acuminata (130-180 mm)as
for homogeous leukoplakias.
During the three years , 14 patients
with leukoplakias, 5 with oral lichen panus and 7 with recurrent benign
aphthosis were treated with PDT.
Irradiation was performed either
with a flashlamp pumped dyes laser or a quasi-cw dye laser at 633nm with
applicators appropriate for the region (microlens, 1800, 3600
isotropic applicator). Some patients if the lesions could not be removed by PDT
had additional CO2-laser treatment .Of the 5 patients with oral
lichen planus, a noticeable improvement of symptoms but not a complete healing
of the lesions has been noticed.
The leukoplakia lesions treated with
TB-O/MB showed a gradual improvement with no side effects, but required up to 5
treatments. In the treatment of leukoplakias side effects were common with ALA,
all patients reported burning sensation during irradiation, and a subsequent
period of swelling of up to 4 days.TB-O/MB-PDT offer a new therapeutic strategy
for recurrent benign aphthosis. It also shows a preventive component: all
patients had experienced more frequent recurrences prior to PDT than after. The
antibacterial effect of TB-O/MB may be responsible for this. On the other hand,
PDT of leukoplakias is more time consuming compared to the established
treatments and show no clear benefits regarding side effects and long time
results. For the 7 patients with RBA was an Energy density of 42-79 J/cm2genügend. For the effective treatment
of the 14 patients with leukoplakias as for the 5 patients with oral lichen
planus more as the double Energydensity had to be applied (72-178 J/cm2).
With the neu Applicators was eine homogenous irradiation possible. More studies
with larger number of patients and longer treatmentstime are needed to evaluate
PDT as an alternative treatment method. |
