Using Light to Kill Tumours
Canadian Cancer Society Funded Research
Leads to Promising Treatment
TORONTO, Nov. 25 /CNW/ - A cutting-edge cancer treatment that uses light
to kill tumours is being heralded as a major therapeutic option for cancer
patients. The treatment - called photodynamic therapy (PDT) - has minimal side
effects, can be given on an out-patient basis and has been curing some
patients with early-stage cancer.
"Photodynamic therapy has successfully moved from the lab to the hospital
and patients are experiencing the many benefits this treatment has to offer on
a daily basis," says Dr. Brian Wilson - a driving force behind this research
since the early '80s - at a Canadian Cancer Society media conference held at
Toronto's Princess Margaret Hospital. "In many cases, patients are being cured
through this treatment. In other cases, PDT is proving to be an effective
addition to the more standard cancer treatments of surgery, radiation and
chemotherapy."
Thanks to funding from the Canadian Cancer Society (almost $2 million
since 1982) Dr. Wilson's studies have paid off in a treatment that is proving
to be effective against many types of solid tumours. Currently, the most
successful applications of PDT - in which patients have a good chance to be
cured - are for early-stage esophogeal cancer and a precancerous condition
called Barrett's Esophagus. PDT is also showing great promise for treatment of
skin, brain and early-stage lung cancer. Treatment by PDT also greatly
improves the quality of life of some patients with advanced cancer.
"The funding that my research has received from the Canadian Cancer
Society was absolutely critical," says Wilson. "It gave us our start and the
chance to build a foundation of knowledge from which we are now seeing these
incredible results today. Canadian Cancer Society volunteers who raise the
crucial funds for cancer research should all feel a part of this achievement -
we simply couldn't have done it without them."
At the heart of PDT is a class of drugs known as photosensitizers. "These
drugs don't become active until exposed to light," explains Dr. Wilson, Head
of the Division of Medical Biophysics at the Ontario Cancer Institute and
Professor of Medical Biophysics, University of Toronto. "The drugs are 'picked
up' by cancerous tissue, then they are activated by a light source. Once
activated, the drugs generate chemicals that kill the cancer cells, either
directly or by destroying the blood vessels supplying the tumour."
In the right patients, PDT can deliver an outright cure. Michael Nolan of
St. John's, Newfoundland was diagnosed in 1994 with early esophogeal cancer.
Doctors offered him a choice between surgery or a six-month course of
chemotherapy and radiation treatment.
By sheer coincidence, Mr. Nolan's wife had just read about PDT in the
local paper and had kept the clipping. Mr. Nolan sent his medical records to
Dr. Norman Marcon in Toronto and was told he was a good candidate for PDT.
(Dr. Marcon, Head of the Therapeutic Endoscopy Centre at Wellesley Hospital
and Associate Professor of Medicine, University of Toronto, has been working
closely with Dr. Wilson for several years, administering photodynamic therapy
to patients.) In November 1994, Mr. Nolan travelled to Toronto to receive
treatment at Wellesley Hospital.
"I was given Photofrin (a light-sensitizing drug) on Saturday," he
recalls. "On Monday I went in and they put a light down my throat to irradiate
the tumour. A few hours later my wife and I went and had breakfast at a
restaurant."
The procedure was repeated again a year later. Since then, Mr. Nolan has
been examined by endoscope each year. Five years after the original procedure,
there is still no sign of his tumour recurring.
PDT can also be used to head off cancer before it occurs. In 1996,
William Perdue of Oakville, Ontario was diagnosed with severe dysplasia
(abnormal development of tissue) of the esophagus, often a precursor to
cancer. Doctors gave him the option of having his esophagus removed - a risky
procedure with radical lifestyle implications - or PDT.
Mr. Perdue opted for PDT and was treated in the fall of 1997 and again in
March 1998. "After the second procedure, biopsies showed that the dyplasia was
gone," he says. "Endoscopy showed that my esophagus is still normal as of this
fall. For me, PDT was a very successful alternative to surgery. I'm extremely
thankful this procedure was available."
Dorothy Lamont, Chief Executive Officer of the Canadian Cancer Society
and its research partner the National Cancer Institute of Canada, says that
"the Canadian Cancer Society is extremely proud to be providing the funding
for Dr. Wilson's research, which is having such a profound effect on cancer
patients."
"Dr. Wilson's project is just one excellent example of the impact that
CCS-funded research has on controlling cancer in Canada. Our mission is to
eradicate cancer and it is this type of research that is moving us towards
this goal."
Lamont says that the Canadian Cancer Society contributed over $40 million
last year to fund cancer research across Canada. "We applaud the efforts of
our volunteers across the country who worked so tirelessly to raise these
funds from caring Canadians. We also salute the extraordinary generosity of
our donors in Ontario, who contributed more than $25 million of this amount.
This $25 million includes an extra $4 million that was donated above and
beyond the CCS's goal of raising $21 million for cancer research in Ontario."
Lamont adds that while the Canadian Cancer Society is proud of its role
in Dr. Wilson's research, it's important that vital cancer research continues.
"We've come a long way in controlling cancer through research, but we still
need to know so much more. The continued generosity of Canadians and the
dedication of our volunteers will, hopefully, lead us to the day when cancer
will be beaten once and for all."
The Canadian Cancer Society is a national, community-based organization
of volunteers whose mission is the eradication of cancer and the enhancement
of the quality of life of people living with cancer. The CCS directs the money
it raises for cancer research to its research partner the National Cancer
Institute of Canada. The NCIC ensures that the money received from the CCS is
directed to the best cancer research in Canada through a strict scientific
review process.
Media Backgrounder
Canadian Cancer Society Funding of Cancer Research
- The Canadian Cancer Society (CCS) provided more than $40 million to
fund cancer research in Canada in its last fiscal year (October 1998 to
September 1999). This was the largest single contribution to cancer
research in Canada. This $40 million supported approximately 221 cancer
research projects across the country. The $40 million also included the
CCS's contribution to breast cancer research and clinical trials.
- The Ontario Division of the Canadian Cancer Society contributed more
than $25 million to cancer research - $4 million above and beyond its
goal for the year (fiscal year October 1998 to September 1999). There
were approximately 137 cancer research projects in Ontario supported by
CCS funds last year. The $25 million also included the CCS's
contribution to breast cancer research and clinical trials.
- All money raised by the Canadian Cancer Society for cancer research is
directed to its research partner the National Cancer Institute of
Canada (NCIC). The NCIC ensures this money is directed to the best
cancer research in Canada through its strict scientific review process.
The CCS also provides funds for public education, patient services and
its Cancer Information Service (1-888-939-3333).
- The Canadian Cancer Society is the largest single funder of cancer
research in Canada.
Media Backgrounder
Photodynamic Therapy
- At the heart of photodynamic therapy (PDT) is the use of of light-
activated drugs.
- Certain drugs (photosensitizers) are activated by light (usually red)
to generate chemicals that kill tumour cells. The photosensitizers or
light by themselves have no effect - only when they are used in
combination are they effective.
- Photodynamic therapy presents a new approach for eradicating solid
tumors. It can be used alone or in combination with other therapies:
radiation, surgery or chemotherapy.
- Photodynamic therapy can be applied to many sites in the body (e.g.
skin, lung, esophagus, brain, bladder, genital tract, etc.) by using
optical fibers to deliver the light from a laser to the tumour.
- Canada is a world leader in PDT:
- Several internationally-known research groups in Canadian
universities and medical research centres are studying PDT;
- QLT Phototherapeutics Inc., based in Vancouver, British Columbia, is
the leader in developing the drug Photofrin and new second-generation
drugs that are key to the success of photodynamic therapy;
- Canada was the first country in the world to approve PDT (in 1993);
- The majority of research into PDT has been supported by Canadian
research agencies. The Canadian Cancer Society has provided almost $2
million in funding for Dr. Brian Wilson's photodynamic therapy
research since 1982.
- Using the drug Photofrin (QLT Phototherapeutics Inc., Vancouver, BC),
PDT has been approved in several countries for different applications:
- recurrent bladder and esophageal cancers in Canada;
- certain lung cancers in the USA;
- several types of early cancer in Japan and various cancers in Europe.
- New technologies are being developed to further refine PDT including
improving light generation, delivering light more accurately to the
tumour or diseased tissue, and monitoring the treatment in individual
patients.
- Dr. Wilson is studying ways to fine-tune dosing in PDT and to measure
the effects of treatment at the earliest possible stage. "We want to
be able to tailor treatment to the individual patient, then to check
as soon as possible whether we've destroyed the tumour," he explains.
"If we've missed a region, or if the response isn't going to be
adequate, we'd like to know right away, so we can repeat the
treatment on the spot, and get it exactly right."
- New photosensitizers with improved selectivity for disease are also
being developed and tested in clinical trials. One major advantage of
PDT is that it is so selective. Because just the cancer site is exposed
to light, anti-cancer chemicals are only created within the tumour
itself. As a result, photodynamic therapy kills only cancer cells, not
healthy ones. This reduces side effects to a minimum. PDT patients do,
however, remain light-sensitive for several weeks after treatment, and
must avoid natural light or risk a sunburn-like reaction. Newer
photosensitizers, now being studied by Dr. Wilson, may not even cause
this unwanted effect.
- In combination with new early-detection methods, PDT helps achieve the
strategic mission to 'search and destroy' tumours.
- PDT is set to become a major new form of therapy, with applications
across many major types of disease.
- Several new drugs are under development and clinical trials are
underway to test PDT for many different conditions in addition to
cancer:
- to control psoriasis and other skin diseases;
- to prevent progression to blindness in macular degeneration;
- to reduce the severity of rheumatoid arthritis;
- to eliminate the need for hysterectomy in endometrial disease;
- to prevent re-blockage of arteries after angioplasty for coronary
artery disease.
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For further information: Kerstin Ring, Manager, Communications, Canadian
Cancer Society, (416) 934-5664; Sylvie Charland, Senior Communications Officer
(Bilingual), Canadian Cancer Society, (416) 934-5681 |
