Photodynamic therapy (PDT)
Photodynamic therapy (PDT) is a treatment that involves the use of a light-sensitive medication and a light source to destroy abnormal cells.
It can be used to treat some skin and eye conditions, as well as certain types of cancer.
On their own, the medication and light source are harmless, but when the medication is exposed to the light, it activates and causes a reaction that damages nearby cells.
This allows small abnormal areas of tissue to be treated without the need for surgery.
Uses of PDT
PDT can be used to treat abnormalities in parts of the body a light source can most easily reach, such as the skin, eyes, mouth, oesophagus (gullet) and lungs.
Conditions sometimes treated with PDT include:
actinic keratoses – dry scaly patches of skin caused by damage from years of sun exposure that could become cancerous if not treated
Bowen's disease – a very early form of skin cancer
basal cell carcinoma – a type of skin cancer
macular degeneration – an eye condition that can lead to vision loss
Barrett's oesophagus – changes in the cells in the lining of your lower oesophagus that could become cancerous if not treated
oesophageal cancer, mouth cancer and lung cancer – PDT can cure some cancers if used in the early stages, or offer relief from symptoms in more advanced cases
PDT also shows promise in treating other conditions, such as warts,acne and some other types of cancer.
Despite the claims relating to unproven “alternative” forms of PDT, such as next-generation PDT and sonodynamic therapy, PDT is not effective at treating widespread conditions or those affecting deeper parts of the body where a light source cannot reach.
In these cases, surgery, radiotherapy, and/or chemotherapy may be recommended instead.
PDT is carried out in two stages.
First, you will need to come into the hospital or clinic to be given the light-sensitive medication. Depending on the area of the body being treated, this can be a cream, injection or special drink.
Once the medication has been applied or given, you may be asked to go home and return in a few hours or days. This will give the medication a chance to build-up in the abnormal or cancerous cells that are going to be treated.
Later, you will need to return to the hospital or clinic for the light treatment. This will involve a lamp or laser being shone onto the treatment area for around 10-45 minutes. To treat abnormal cells inside your body, such as in your lungs, an endoscope (flexible tube) will be passed into your body to deliver the light.
You will usually be able to go home the same day you have the light treatment.
If your skin was treated, it will be covered by a dressing that will need to remain in place for at least two days. You should try to avoid scratching or knocking the treated area, and keep it as dry as possible.
Once you are advised to remove the dressing, you should be able to wash and bathe as normal, although you should make sure you pat the treated area dry gently.
A follow-up appointment at the hospital or clinic will be arranged to assess whether the treatment has been effective and decide if it needs to be repeated.
It will usually take around two to six weeks for the area to heal completely.
Risks and side effects
PDT is generally a very safe treatment. However, it’s common to experience a burning or stinging sensation while the light treatment is being carried out. This will usually pass soon after the treatment finishes.
PDT can also make your skin or eyes sensitive to light for up to six weeks, even if the area treated was inside your body. This means they may become red and sore when exposed to direct sunlight or bright indoor lights. Your treatment team will advise you about things you should do to protect your eyes and skin.
Other potential side effects will depend on the area treated.
For example, if your skin is treated, it may crust over, and become temporarily red, swollen or blistered after treatment.
Your skin may also become slightly darker or lighter than it was before and there may be some hair loss. This is usually temporary, but it can sometimes be permanent.
Treatment of the mouth, oesophagus and lungs can cause temporarycoughing, difficulty swallowing, painful breathing, or breathlessness.
If your eyes are treated, there is a small risk of permanent vision loss.
Make sure you talk to your doctors about the possible risks and benefits of PDT before you agree to treatment.
Next-generation PDT (NGPDT) and sonodynamic therapy (SDT)
PDT as described above is an effective and licensed treatment for a number of conditions. It should not be confused with the unproven, unlicensed versions sold by some private clinics in the UK and overseas.
Clinics promoting these so-called "advanced" versions of PDT, called "next-generation PDT" (NGPDT) and "sonodynamic therapy" (SDT) claim they can treat deep or widespread cancers, but these claims aren't supported by scientific evidence and these treatments aren't recommended.
Next-generation PDT and sonodynamic therapy
Conventional photodynamic therapy (PDT) is an effective and licensed treatment for a number of conditions. It shouldn't be confused with unproven, unlicensed versions of PDT sold by some private clinics in the UK and overseas.
These so-called "advanced" versions of PDT, called "next-generation PDT" (NGPDT) and "sonodynamic therapy" (SDT), are not supported by scientific evidence.
Certain private clinics in the UK, Mexico and China promoting NGPDT and SDT have been criticised for falsely claiming that these therapies can treat late-stage cancers. Medical experts critical of these clinics believe the people running them are misguided or fraudulent.
If you or your child are seriously ill with cancer, it's understandable to feel desperate and want to try every available treatment that might help.
However, if you opt for NGPDT or SDT rather than trusted medical advice and treatment, you could be putting your life at risk. Your condition may deteriorate further and you may experience unknown side effects from the therapy.
NGPDT and SDT shouldn't even be used as a last resort for incurable cancer, as they may result in unnecessary pain and you may be faced with unaffordable costs, as the recent tragic story of Olivia Downie highlights (see below). The treatment typically costs in the region of £10,000.
Clinics promoting NGPDT and SDT market these therapies as "advanced forms" of PDT.
They sell NGPDT and SDT as natural, non-invasive therapies that use non-toxic light-sensitive substances such as chlorophyll.
These clinics claim the substances they use "explode" with oxygen, killing the cancer cells when they are activated not only by light, but also by ultrasound waves, which can apparently reach every part of the body.
They claim they can effectively treat deep or widespread cancers such as advanced liver cancer or neuroblastoma.
This is in contrast to conventional PDT, which can only have an effect through tissue at a depth of up to about 1cm and is only used to treat areas where a light source can easily reach.
What reputable health experts say
Most health experts believe that people running such clinics are either misguided or exploiting vulnerable members of the public for commercial gain.
None of the above claims are supported by scientific evidence, and stories such as Olivia Downie's (see below) reinforce the knowledge that these treatments can be harmful.
The use of NGPDT and SDT is not recommended by the 2010 critical appraisal of a clinical application of sonodynamic therapy (PDF, 327kb)concluded that:
"There is no convincing data that shows that ultrasound used in this way is effective in the treatment of primary tumours and multiple metastases [cancer that has spread]."
The authors of this appraisal also questioned how the superficial light source used can reach the deep-seated cancers in lung and bone tissues.
Furthermore, concerns were raised about the use of unproven interventions in terminally ill cancer patients, as without information proving that these unconventional techniques and substances are safe and effective, it's arguably unethical to offer them to patients – particularly those who are near the end of their life and very weak.
In June 2012, seven-year-old Olivia Downie from Aberdeenshire travelled to a clinic in Mexico. She was seriously ill with neuroblastoma (a rare cancer of the nervous system) and the could do no more for her.
Her mother says she hoped that the Mexico treatment would relieve Olivia's pain, which even morphine couldn't control, and extend her life for a few more months. It was her last hope.
But the treatment – sonodynamic therapy – did nothing to help Olivia. She got much worse and an ambulance was called. Olivia was put on a life-support machine and transferred to a private Mexican hospital.
Her parents were forced to appeal for money to fly her home in an air ambulance. Their pleas for her to be brought home to die touched many people and more than £150,000 was donated.
Olivia died within 48 hours of her return. Her mother deeply regrets making the trip.
The Guardian, August 24 2012: "How children's cancer is making parents 'stab in the dark' for treatment"
Photodynamic therapy (PDT)