3 juni 2018: lees ook dit artikel: 


d.d. 21 oktober 2003:

Dr. Ida Stender schreef een overzichtsartikel over het gebruik en effect van PDT - Photodynamische Therapie - met zalf genaamd Metvix en Levulan voor gezichts behandelingen van voorstadia van huidkanker en plaveiselcarcinomen (basecellcancer) van huidkanker in de plaats van operatieve verwijdering en/of bevriezing (cryosurgery). Bv. zij meldt dat de kans op geen terugkeer in een studie bij 169 patiënten met voorstadia van huidkanker op korte termijn - drie jaar - bij bevriezing lag op 75% t.o. 69% bij PDT, maar op langere termijn lag de kans op terugkeer/recidief op 25% bij beide technieken gelijk. Bovendien ervaarden de patiënten de PDT-behandeling als prettiger en minder ingrijpend. Opvallend is dat dr. Stender beweert dat PDT voor diepliggende tumoren zoals bv. melanomen nooit een officiële behandeling zal worden.

Bron: DOW-news d.d. 21 oktober 2003:

-- WSJ(10/21) Personal Health Report: A New Treatment For Skin Cancer Calls For Rem --

By Xueling Lin
COPENHAGEN -- A promising new skin-cancer therapy can make the disease disappear without the scars of surgery.
The treatment, known as photodynamic therapy, uses medicinal creams and intense light to kill the cancer. The prospect of a surgery-free treatment is particularly appealing to skin-cancer patients, who commonly cope with lesions on their faces, where disfiguring scars matter the most. Even so, many doctors have yet to embrace the therapy, saying they are still
waiting for long-term data on recurrence rates. Studies show that traditional surgery is still more effective than the cream-and-light treatment, raising concerns that the light therapy risks leaving some cancer behind. Questions also remain about patient comfort, convenience and cost.
But supporters say the cosmetic benefit of avoiding surgery probably is worth a slightly higher chance of recurrence, particularly with the milder forms of skin cancer. "If a patient comes in with a single, small precancerous spot, it's tempting to go for traditional curettage [cutting or scraping with a surgical tool known as a curette], since this is a fast and effective form of treatment," says Ida Stender, a dermatologist in Copenhagen who wrote a Ph.D. thesis on photodynamic therapy, or PDT. "But if the spot is located on the person's nose,"
Dr. Stender continues, "a place everyone can see and that the patient herself will see everyday in the mirror, you have to consider if PDT is a better alternative."

Currently, the treatment is used primarily for actinic keratosis, the most common form of premalignant skin tumor. Actinic keratosis is where the skin cells are not yet cancerous, but the cells are no longer normal and with time could become cancerous. In places like Australia, where sun exposure is notoriously high, about 40% of the population will have the small tumors that characterize actinic keratosis, and the figure rises to nearly 100% for people over the age of 70. Typically, the cancers aren't fatal and are removed with
simple cryosurgery, the widely used method of freezing thin tumors that are close to the skin with liquid nitrogen. Doctors say that only a fraction of those with actinic keratosis actually get treated at present. An estimated 10 million people in the U.S., Europe and Australia seek treatment for the disease each year, although around 20 million new cases develop every year.

One of them is 63-year-old Danish homemaker Alice Meier. Ms. Meier travels 200 miles every three months from her home in the small town of Hjorring to seek the light treatment from Dr. Stender in Copenhagen. Ms. Meier suffers from a severe form of the disease. Over the past three decades, she says, she has had at least 1,000 small tumors surgically removed from her face, head and neck with a
curette. "It reached the point where I couldn't see a curette without feeling nauseous," says Ms. Meier.
But with PDT, a cream is rubbed on the tumors. The cream is left to penetrate the skin over several hours, and the tumor is then exposed to intense light for six to 15 minutes. The light makes the cancerous cells turn red and puffy like a small scald burn. After a few days, the area blisters and a scab containing the dead cancer cells appears. After a week to 10 days, the scab falls off and the
healthy skin underneath is revealed. Says Ms. Meier, "It heals much faster, and the cosmetic result is fantastic."

PDT works by exploiting two natural functions: the ability of healthy cells to ward off substances that can harm them, and the tendency of certain acids in the body to become active when exposed to light. When a cream containing one of these light-sensitive acids is applied to the cancerous area, healthy cells wash it out and sick cells retain it. Then, a bright light is shot at the spot,
activating the acid, which makes the sick cells burn up and die. Surgery still appears to be the most effective treatment in cases where the tumor extends deep into the skin, and in cases of another common form of skin cancer, basal-cell carcinoma, which afflicts an estimated two million people a year world-wide. "It's not how big the skin cancer is that determines whether PDT is the right
treatment, it's how deep the cancer is," says Dr. Stender. "There's a limit to how far the cream and the light can penetrate."

It's unlikely that any form of the light therapy will be used for melanoma, the most serious and deadly form of skin cancer that still must be surgically removed. Still, even in some cases where surgery is required, PDT can significantly reduce the amount of cutting needed, doctors say, which ultimately will reduce the size of the scar that is left. "You use PDT to remove shallower skin
cancers, and then you look to see what's left," says Dr. Stender. "These smaller areas where the deeper cancers are can then be removed by surgery."

Currently, two companies offer similar photodynamic therapy treatments.
Photocure ASA, a Norwegian biotechnology company, makes Metvix, launched in
Sweden in 2001. Dusa Pharmaceuticals Inc., a biopharmaceutical company based in
Wilmington, Mass., makes Levulan, which was introduced in 2000. The creams both
appear effective, but there are two main differences. One is timing -- Metvix is
left on for three to four hours before the light treatment, while Levulan is
left on for 14 to 18 hours before being followed by light therapy. The other
difference is the light used -- a blue light for Levulan, red for Metvix.
However, doctors say it isn't possible to judge which is better since no
head-to-head studies have been done comparing the two products.
Though PDT is promising, studies show that both traditional surgery and
cryosurgery likely are still more effective for tumors deep into the skin. In
one short-term study of the treatment, published in the Journal of the American
Academy of Dermatology, researchers at the University of Regensburg in Germany
treated 699 actinic-keratosis lesions on 193 patients using either PDT or
cryotherapy. After three months, that study found, the response rate for PDT was
69%, lower than the 75% for cryotherapy. However, patient satisfaction about the
cosmetic result was higher in the case of PDT: 98% of patients thought the
cosmetic outcome of PDT was excellent or good, compared with 91% in the
cryotherapy group.
So far the only long-term studies of the two PDT treatments have been
conducted by the two companies themselves. A smaller Photocure study comparing
PDT with traditional surgery found that after two years, surgery failed just 3%
of the time, while 15% of the PDT-treated lesions came back. However, a
comparison of cryosurgery and PDT over three years showed recurrence rates in
both groups of 25%.
Photocure has won approval in much of Europe for treatment of both actinic
keratosis and basal cell carcinoma. The U.S. Food and Drug Administration has
granted Photocure approval for actinic keratosis, and the company has applied
for FDA approval of Metvix for treatment of basal cell carcinoma. Photocure also
has approval in Australia for treating basal cell carcinoma in cases where
surgery is considered inappropriate.
Dusa's Levulan has been approved for treatment of actinic keratosis in the
U.S., Canada and Brazil. Chief Executive Geoffrey Shulman says the company would
like to get approval in Europe at some point but has no immediate plans to seek
it. "We decided we should concentrate on the U.S. first and get revenues in this
market up," he says.
The company has not tried to get Levulan approved for treatment of basal cell
Meanwhile, even though PDT is gaining widespread acceptance by health
agencies, it may still take a while before it is widely practiced -- even for
actinic keratosis.
"This treatment faces the same issues as any other medical treatment -- did
you kill all the cancer cells? Will it come back?" says David Leffell, professor
of dermatology and surgery at Yale University School of Medicine in New Haven,
Some doctors say that despite the apparent cosmetic benefits of PDT, the
treatment may actually be more painful for patients. "In cryosurgery, there is a
short burst of cold, while in PDT the period of pain can be more prolonged,"
says Don Miech, clinical professor of dermatology at the University of
Wisconsin. "I'll probably wait until there is compelling evidence to show that
PDT is superior to present modalities."
Cost is also a factor. There are no exact figures on how much more expensive
PDT is compared with surgery, but PDT treatments do require more equipment and
the purchase of the cream, which costs about $150 to treat two to four tumors.
And some patients don't like the hours of waiting time and second trip to the
doctor's office required for PDT therapy.
"The barrier to adoption of this treatment has been, in my opinion, the
inconvenience factor," says Dr. Leffell.
Dermatologists like Dr. Stender, however, say the cosmetic advantages of PDT
should not be overlooked. Dermatologists also say PDT is very useful in cases
where if surgery alone were used, the doctor would have to cut away large areas,
which often would be hard to close and would leave ugly scars. "PDT saves skin
and sometimes [when the cancer is on the scalp] it can save hair, which isn't
unimportant for most patients," says Dr. Stender.
Another group that has become very interested in PDT -- even for treatment of
basal cell carcinoma -- is liver- and kidney-transplant patients. Transplant
patients use immuno-suppressant drugs to stop their bodies from rejecting the
donor organ. But one of the side effects of taking those drugs is a tendency to
develop skin cancers. Indeed, studies have found that skin cancer is the most
common cancer found in transplantation patients.
Jorg Karlgaard, a 39-year-old Norwegian doctor, had a kidney transplant when
he was 15. "Because I use immuno-suppressants, I started to develop skin
problems, and last year I developed basal cell carcinoma," he says.

Plaats een reactie ...

Reageer op "Huidkanker: PDT - Photodynamische Therapie met Metvix en Levulanzalf succesvol bij plaveiselcarcinomen van huidkanker (basecellcancer) en voorstadia van huidkanker. "

Gerelateerde artikelen

Gerelateerde artikelen

Huidkanker: PDT - Photodynamische >> Huidkanker: PDT - Photodynamische >> Huidkanker: PDT - Photodynamische >>