Biomedical Engineering Reference
In-Depth Information
They found no signifi cant difference (50% in the ALA-PDT
group vs. 52.7% in the placebo-PDT group) between groups
with regard to recurrence rates up to 12 months after treat-
ment. Interestingly, use of an ablative CO
2
fractional laser for
removing the upper parts of hyperkeratotic wart lesions fol-
lowed by MAL application showed 100% clearance in 90% of
lesions after a mean of 2.2 treatments (241). Thus, perhaps use
of MAL or ALA ointment applied after CO
2
laser ablation of
the lesion should allow better penetration of the drug and
allow enhanced effi cacy of PDT in the treatment of warts.
Therefore, topical PDT appears to be a potential resource
against viral warts. It is a safe and wart-selective therapy, leav-
ing excellent esthetic results. The treatment, however, is time-
consuming for patients, requires the use of a keratolytic agent
pre-PDT and it can be very painful as well.
due to temporary suppression of Langerhans cells in the
epidermis (250). In addition, transcription factors, especially
AP-1, Nf
B, and subsequently different cytokines are induced,
which infl uence infl ammatory cells within the epidermis and
the dermis as well as fi broblasts (251,252). Case series and
individual reports describe the potential of topical PDT in a
variety of other indications that include localized scleroderma
(253), lichen sclerosus (254), hidradenitis suppurativa (255),
sarcoidosis (256), necrobiosis lipoidica (257), infl ammatory
linear verrucous epidermal nevus (258), among others.
Finally, there is evidence that topical PDT can be effective
in cutaneous infectious disorders that include cutaneous leish-
maniasis (259,260), recalcitrant molluscum contagiosum (261),
and onychomycosis (262).
κ
future directions
PDT, with a variety of lasers and light sources, is changing how
many dermatologists and laser surgeons look at a variety of
diseases/entities for which they are using the devices in their
clinical practices. ALA- and MAL-PDT has found its niche
in the treatment of photorejuvenation and associated AKs,
if present. It has also found its niche in the treatment of mod-
erate to severe inflammatory acne vulgaris. Other entities,
including sebaceous gland hyperplasia and recalcitrant hid-
radenitis suppurativa are also being treated successfully and
routinely with ALA-PDT. Superficial skin cancers and BD are
also regularly treated with ALA- and MAL-PDT. More and
more entities will continue to be studied with PDT and its use
expanded in the next several years. The future for this type of
therapy looks very bright.
Psoriasis Vulgaris
Limited evidence indicates PDT to be of benefi t for psoria-
sis (242). A small study of four patients comparing topical
PDT (20% ALA, 4 hours under occlusion, 630 nm, 10 J/cm
2
,
120 mW/cm
2
) with narrowband UV-B therapy showed that
topical PDT was inferior in inducing clinical response and
remission and was poorly tolerated by patients because of
pain (243).
Schleyer and colleagues (244) conducted a randomized,
double-blind intrapatient comparison study in 12 patients
with psoriasis treated with 0.1%, 1%, and 5% ALA (4-6 hours
under occlusion, 600-740 nm, 20 J/cm
2
, 60 mW/cm
2
) and
found limited mean improvement of 37.5%, 45.6%, and
51.2%, respectively. Furthermore, irradiation had to be inter-
rupted several times because of severe burning and pain
sensation.
Apparently, good results were achieved in a dose-ranging
PDT study with a single oral dose of 5-15 mg/kg ALA and
irradiation with blue light, 1-6 hours after ALA administra-
tion (245). Improvement was noted in the 15 mg/kg group
only, with a 42% reduction in plaque severity compared with
baseline. In contrast to topical ALA-PDT, tolerability was
excellent, with no patient complaining about pain during sys-
temic PDT.
Overall, topical PDT does not appear to be a practical ther-
apy for psoriasis, due to the disappointing clinical response,
very slow improvement and unpredictable occurrence of pain
related to irradiation.
conclusion
PDT is a safe and effective treatment for nonhyperkeratotic
lesions. Although FDA-approved for use with a blue and red
light source, other laser and light sources have demonstrated
promise in the treatment of AKs during PDT. Shorter incuba-
tion times maintain AK clearance rates but decrease the occur-
rence of phototoxic adverse events. With careful patient
selection, PDT allows selective fi eld treatment of precancerous
skin lesions with improvement in overall photodamage.
Patient satisfaction is high and cosmetic results can be excel-
lent. Strong evidence confi rms the high effi cacy of topical
PDT in BD, superfi cial BCC, and also in thin nBCC, following
lesion preparation, as demonstrated by comparison studies.
other indications
Topical PDT has been studied in many other dermatologic
conditions that are beyond the scope of this chapter. Other
oncologic cutaneous conditions studied include cutaneous
lymphoma T-cell lymphoma (CTCL) with case reports and
case series (246,247) showing successful topical ALA- and
MAL-PDT for early-stage localized CTCL after multiple treat-
ment sessions and extramammary Paget's disease (EMPD).
Although there are limited cases reported with high recurrence
rates (248,249), PDT, particularly using systemic photosensi-
tizers, might be a useful, surgery-sparing therapeutic option
for management of noninvasive EMPD in selected patients.
In infl ammatory skin diseases, modulation of cellular func-
tions, rather than cell death, is the main mechanism of action.
It appears that PDT is involved in a minor immunosuppression
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