Athena
04-15-2008, 04:19 PM
Shine a light at the cancer and it will go away
PDT shows success in head-and-neck cancers
http://www.rodeodriveplasticsurgery.com/images/phototherapy.jpg
Shine a light at the cancer and it will go away. This sounds like advice from a mythical fairy godmother, not a de******ion of a 21st century oncology. However, for certain indications, light therapy may prove to be a viable alternative to more conventional cancer cures.
The photodynamic treatment of cancer is (unsurprisingly) slightly more complicated that the above de******ion suggests. Therapy is a two stage process. Patients first receive a drug that makes cells more sensitive to light. This agent homes in on cancer cells so that the effect is maximized in the tumour. After a suitable delay - to let the drug reach its target - light is directed at the cancer. The drug is activated by the light and the photosensitized cancer cells are destroyed.
Photodynamic therapy (PDT) is already being used to treat a variety of easily accessible cancers. Suitable targets include the lining of the mouth, lung, oesophagus, stomach, bladder and bile ducts. It has also been used to treat non-melanoma type skin cancers.
Merrill Biel, surgical oncologist at the Virginia Piper Cancer Institute (Minneapolis, MN) believes that PDT could also be applied to many head-and-neck cancers. This conviction is supported by results presented at January’s BiOS symposium.
Biel’s data concerned 395 patients with various cancers of the head and neck. In each case, treatment began with a dose of the photosensitizing agent Photofrin (2 mg/kg). Light therapy was performed 48 hours later, with thin fibre-optic cables used to direct the treatment beam (wavelength 630 nm).
For the 125 patients with laryngeal tumours, 102 were categorized as "complete responders". All of these successfully treated cases concerned early-stage carcinomas. Just 10 recurrences were recorded during an extended follow-up period (mean 99 months), giving a cure rate for this group of 91%. This is comparable to what would be expected with a regimen of surgery and radiotherapy.
The 213 patients with oral, nasal and nasopharyngeal tumours experienced similar success. All responded completely to PDT (mean follow-up period 98 months). Eight instances of local recurrence were observed, all within eight months of treatment. Patients with early stage carcinomas again fared best.
Results were less impressive for patients with more advanced, invasive cancers. Of the 24 individuals with this type of cancer, only 15 responded completely and just 11 had "no evident disease" after 190 months. Six patients developed local recurrence within three months.
The lower cure rate reflects the practical difficulties experienced when treating deep, infiltrating tumours, Biel explained. "We still don’t have a good means of measuring whether we are delivering the light uniformly to the entire tumour bed," he said.
Surgical adjunct
In addition to its use as a standalone cure, PDT may also help stop persistent head-and-neck cancers from re-growing after surgical resection, Biel noted. "The idea is that the photodynamic therapy will kill any microscopic cancer cells that may be remaining at the margins of the resection bed," he said. "For large tumours, we know that despite doing very large resections, and following up with radiation and chemotherapy, we still have very high local recurrence rates."
A strategy of surgery followed by light therapy was trialled on 18 patients with recurrent, infiltrating head-and-neck cancers at the Virginia Piper Cancer Institute. Once again, Photofrin was administered 48 hours in advance of therapy. The tumour was removed and light directed at the open resection bed. Six recurrences were recorded during 176 months of follow-up. Four of these were outside of the PDT field, and two within the region treated with light.
PDT has no long-term side-effects, can be repeated at the same site, and is highly selective, Biel said. Treatment of oral tumours will not leave patients with a dry mouth - as irradiation does. Patients with laryngeal tumours need not fear damage to healthy vocal cords, or long-term problems with swallowing.
The main side-effect associated with PDT relates to the photosensitizing agent. Some Photofrin will be taken up by skin cells, leaving patients prone to sunburn simply by walking outside during the daylight. This inconvenience is thankfully short-lived.
The photodynamic treatment of head-and-neck cancers is relatively limited at present. Photofrin is the only photosensitizing agent to be approved for clinical use in the US, but its approval by the Food and Drug Administration does not cover treatment of head-and-neck cancers. Doing so would be regarded as an off-label application. Practitioners must also seek additional ethical approval to use the thin, fibre-optic cables required to direct laser light at the tumours.
for more information about PDT See,
Link (http://www.christie.nhs.uk/patients/booklets/pdf/pdt.pdf)
//...//
PDT shows success in head-and-neck cancers
http://www.rodeodriveplasticsurgery.com/images/phototherapy.jpg
Shine a light at the cancer and it will go away. This sounds like advice from a mythical fairy godmother, not a de******ion of a 21st century oncology. However, for certain indications, light therapy may prove to be a viable alternative to more conventional cancer cures.
The photodynamic treatment of cancer is (unsurprisingly) slightly more complicated that the above de******ion suggests. Therapy is a two stage process. Patients first receive a drug that makes cells more sensitive to light. This agent homes in on cancer cells so that the effect is maximized in the tumour. After a suitable delay - to let the drug reach its target - light is directed at the cancer. The drug is activated by the light and the photosensitized cancer cells are destroyed.
Photodynamic therapy (PDT) is already being used to treat a variety of easily accessible cancers. Suitable targets include the lining of the mouth, lung, oesophagus, stomach, bladder and bile ducts. It has also been used to treat non-melanoma type skin cancers.
Merrill Biel, surgical oncologist at the Virginia Piper Cancer Institute (Minneapolis, MN) believes that PDT could also be applied to many head-and-neck cancers. This conviction is supported by results presented at January’s BiOS symposium.
Biel’s data concerned 395 patients with various cancers of the head and neck. In each case, treatment began with a dose of the photosensitizing agent Photofrin (2 mg/kg). Light therapy was performed 48 hours later, with thin fibre-optic cables used to direct the treatment beam (wavelength 630 nm).
For the 125 patients with laryngeal tumours, 102 were categorized as "complete responders". All of these successfully treated cases concerned early-stage carcinomas. Just 10 recurrences were recorded during an extended follow-up period (mean 99 months), giving a cure rate for this group of 91%. This is comparable to what would be expected with a regimen of surgery and radiotherapy.
The 213 patients with oral, nasal and nasopharyngeal tumours experienced similar success. All responded completely to PDT (mean follow-up period 98 months). Eight instances of local recurrence were observed, all within eight months of treatment. Patients with early stage carcinomas again fared best.
Results were less impressive for patients with more advanced, invasive cancers. Of the 24 individuals with this type of cancer, only 15 responded completely and just 11 had "no evident disease" after 190 months. Six patients developed local recurrence within three months.
The lower cure rate reflects the practical difficulties experienced when treating deep, infiltrating tumours, Biel explained. "We still don’t have a good means of measuring whether we are delivering the light uniformly to the entire tumour bed," he said.
Surgical adjunct
In addition to its use as a standalone cure, PDT may also help stop persistent head-and-neck cancers from re-growing after surgical resection, Biel noted. "The idea is that the photodynamic therapy will kill any microscopic cancer cells that may be remaining at the margins of the resection bed," he said. "For large tumours, we know that despite doing very large resections, and following up with radiation and chemotherapy, we still have very high local recurrence rates."
A strategy of surgery followed by light therapy was trialled on 18 patients with recurrent, infiltrating head-and-neck cancers at the Virginia Piper Cancer Institute. Once again, Photofrin was administered 48 hours in advance of therapy. The tumour was removed and light directed at the open resection bed. Six recurrences were recorded during 176 months of follow-up. Four of these were outside of the PDT field, and two within the region treated with light.
PDT has no long-term side-effects, can be repeated at the same site, and is highly selective, Biel said. Treatment of oral tumours will not leave patients with a dry mouth - as irradiation does. Patients with laryngeal tumours need not fear damage to healthy vocal cords, or long-term problems with swallowing.
The main side-effect associated with PDT relates to the photosensitizing agent. Some Photofrin will be taken up by skin cells, leaving patients prone to sunburn simply by walking outside during the daylight. This inconvenience is thankfully short-lived.
The photodynamic treatment of head-and-neck cancers is relatively limited at present. Photofrin is the only photosensitizing agent to be approved for clinical use in the US, but its approval by the Food and Drug Administration does not cover treatment of head-and-neck cancers. Doing so would be regarded as an off-label application. Practitioners must also seek additional ethical approval to use the thin, fibre-optic cables required to direct laser light at the tumours.
for more information about PDT See,
Link (http://www.christie.nhs.uk/patients/booklets/pdf/pdt.pdf)
//...//