Photodynamic therapy: from research to treatments
Developing new and improved treatments for cancer takes time. This is something that Professor Stephen Bown, at the National Medical Laser Centre in University College London, knows only too well. He has been studying Photodynamic therapy or (PDT) for more than 20 years, and was funded by Worldwide Cancer Research for 11 of these.
What is PDT and why use it for treatments?
PDT uses a light-sensitive drug that is drawn towards cancerous tissue. The drug only works when activated by red laser light, which can be directed to the cancerous area.
Areas treated by PDT heal remarkably well, meaning less medical intervention after the treatment and minimal upset for the patient. Thanks to more recent research, PDT can also now be used internally, for organs deep in the body and is applied by remote control.
How PDT can help head and neck cancer patients
Worldwide Cancer Research has funded more than 30 grants on PDT since 1986, including 6 for Professor Bown. He aimed to understand how PDT affects healthy tissues in and around the mouth, an essential step to ensure it is safe for use in patients. A key challenge of cancer treatments is to destroy cancers where they start to spread into normal, healthy tissue, without harming the normal tissue.
Mouth cancers affect more than 6,000 people in the UK every year, and the possibility of disfigurement or swallowing or speech impairment after surgery has a very real impact on a person’s quality of life. It is an advantage for patients to be able to avoid surgery, or the side effects of radiotherapy. His work showed that although PDT can affect soft tissues as well as cancerous areas in and around the mouth, there is little effect on bone, and the normal tissues heal safely, with minimal scarring. Professor Bown’s results made it safe to start clinical studies, and more than 2,000 treatments have been carried out on patients at University College Hospital in London over the last 20 years.
Professor Bown said,
It was Worldwide Cancer Research’s support that enabled us to do the research that made it safe to use the drug ALA, and other PDT drugs, for early cancers of the head and neck.
PDT is now used by the NHS for head and neck cancers that have failed all other treatments. It is much cheaper than surgery or chemotherapy, and is importantly, much safer for patients. There is also a big cosmetic advantage, as PDT causes less scarring, making it an attractive option for tumours of the mouth. This can have a considerable impact on a person’s quality of life if the tumour is on an area as prominent as the lips.
Early work on the safety and efficacy of PDT paved the way for the treatment of other cancer types, such as lung, oesophageal, pancreatic, and skin cancer, and some non-cancerous conditions.
A valuable treatment for pancreatic cancer patients
Pancreatic cancer is an aggressive, rapidly progressing disease, which kills more than 300,000 people in the world each year. The cancer can grow for years without symptoms. As a result, it is often diagnosed very late, when the disease is so advanced that surgery is not an option for most patients. It is also a cancer that does not response well to current radiotherapy and chemotherapy, and it remains difficult to treat. But PDT is showing promise.
During the period of his Worldwide Cancer Research funding, Professor Bown spent six years testing whether PDT was safe for the organs surrounding the pancreas. The pancreas is surrounded by many vital organs; so it is important that any new treatment does not cause any unwanted side effects on the shape or function of the normal pancreas or the surrounding organs.
To treat pancreatic cancer, the laser light is delivered directly to the tumour using fine optical fibres passed through thin needles that are inserted through the abdomen. University College Hospital treated the first pancreatic cancer patients by PDT in 1996. More recently, work has focused on improving how PDT is delivered.
How PDT is helping many different patients
Another of Professor Bown’s Worldwide Cancer Research grants helped PDT become a licensed treatment for Barrett’s oesophagus. Barrett’s oesophagus (BO) is a common condition that can sometimes lead to cancer of the oesophagus (food pipe). The same technique is now used for some very early lung cancers in patients who are not fit for more radical treatment.
PDT is also used to treat an eye condition called macular degeneration, and several skin conditions, including a type of skin cancer called basal cell carcinoma.
It is great to see how some of our very early funding, has helped so many cancer patients, and that the impact of this work is even wider reaching, by helping to treat diseases other than cancer too.
Without research like this, funded by your supporters, we would never get better treatments, and survival rates would never improve.
Professor Stephen Bown.