Mesothelioma Photodynamic Therapy (PDT)
This burgeoning treatment for pleural mesothelioma uses light to kill deadly mesothelioma cells. Use of PDT can improve life expectancy with the benefit of fewer side effects.
Killing Mesothelioma Cells With Lasers
Photodynamic therapy is relatively new in the treatment of cancer, but it has been steadily developing into a viable treatment option. This treatment uses laser light to activate a drug that targets and kills mesothelioma cells. Photodynamic therapy has demonstrated positive results in patients with pleural mesothelioma, especially when used in combination with a lung-sparing pleurectomy.
Benefits of Photodynamic Therapy
Fewer Side Effects
This type of treatment is turning out to be a viable alternative to chemotherapy and radiation therapy with markedly fewer side effects.
Recent studies on the effects of photodynamic therapy have shown that it can significantly increase life expectancy. Used in combination with surgery or chemotherapy, PDT is even more effective.
Several clinical trials testing different modalities of the treatment are being conducted. Photodynamic therapy’s success will come from producing methods with fewer side effects and shorter light sensitivity time.
How Does Light Kill Mesothelioma?
Photodynamic therapy relies on the interaction of laser light and a light-sensitive drug known as a photosensitizer. The photosensitizer, administered via injection or IV, is activated when light is applied to the tumor area.
In photodynamic therapy, cells that have absorbed the photosensitizer react chemically with oxygen in the body when light is applied.
This chemical reaction coupled with the laser light effectively kills the cancer cells. Although healthy cells can be attacked in the process, PDT mostly affects mesothelioma cells because they tend to absorb more of the photosensitizer than healthy cells.
The laser light used to activate the photosensitizing drug is delivered via a thin fiber optic filament, which reflects the light to the tumor. The fiber optic filament is passed through an endoscope to reach the tumor site on the surface of the lungs.
Photosensitive Drugs for Mesothelioma
Patients receive the light-sensitive drug 1 to 3 days prior to the light therapy. Mesothelioma cells retain the drug longer than healthy cells allowing for fewer side effects at the time of light treatment. Timing of the light administration is important as tumor cells need time to absorb the photosensitizing drug.
Porfimer sodium, commonly known as Photofrin, is one of the primary drugs being used in photodynamic therapy for mesothelioma. The main benefit of Photofrin is that is has no effect in patients until it has been activated by light. This helps reduce side effects.
Photofrin is the only FDA-approved photosensitizer for intravenous use, although it hasn’t been approved for mesothelioma yet. There are other photosensitizing drugs that are applied topically but are not used for internal cancers like mesothelioma.
Pros and Cons of Photodynamic Therapy
As with any treatment, there are pros and cons to photodynamic therapy. Some of the obvious pros include the fact that it is less invasive and can be used relatively safely in conjunction with other treatments. It is also more precise than chemotherapy and radiation because it only affects cells that absorb the photosensitizing drug.
Photodynamic therapy has relatively few side effects compared to radiation and chemotherapy. There are no long-term side effects and it can be used repeatedly at the tumor site. It’s also generally more affordable than other treatments.
There is evidence that photodynamic therapy damages tumor blood vessels and may even activate the immune system to fight the mesothelioma cells in the body.
Side effects that do occur, but are generally minimal. Sensitivity to light, swelling and achiness at the site of administration are the most common side effects. The predominant con is that photodynamic therapy is usually only useful for surface tumors, such as those related to skin cancer—it can only affect areas that can be reached by the light.
A Note On Light Sensitivity
The photosensitizing agent administered to patients undergoing photodynamic therapy collects in healthy cells throughout the body. This makes these cells sensitive to sunlight and some other artificial light as well. Skin cells and cells in the eyes that have absorbed Photofrin, for example, make the patient more vulnerable to burning.
These effects can develop quickly, so patients who have been given Photofrin have to take care to protect themselves. The length of time patients are sensitive to light varies from 30 days to 3 months. It should also be noted that sunscreen only blocks UV radiation and will not prevent a photodynamic reaction.
Intraoperative Photodynamic Therapy
The main roadblock to photodynamic therapy being used as an effective treatment for mesothelioma is the nature of mesothelioma tumors. These tumors are usually numerous and scattered throughout the chest. They are also typically embedded deep in the lungs and chest, which can make it hard to apply light to the tumor site.
Intraoperative photodynamic therapy offers a clear solution to this problem since the light can be applied directly to tumors during surgery. Intraoperative photodynamic therapy also has a shorter recovery time than intraoperative chemotherapy or radiation.
Intraoperative photodynamic therapy is typically used in conjunction with a lung-sparing pleurectomy. The benefit of this treatment over intraoperative radiation is that there is a much lower level of toxicity to the lung so patients tend to retain a better quality of life. Patients who are eligible for surgery may be able to take advantage of this treatment through clinical trials.
Intraoperative Photodynamic Therapy
Photodynamic Therapy Improves Life Expectancy
One study, concluded in 2012, found that intraoperative photodynamic therapy combined with pleurectomy is a successful approach to treating mesothelioma. In the study, 97 percent of patients had advanced stage pleural mesothelioma yet the median survival time was 41.2 months for those with an epithelioid cell type (the most common cell type).
If you have pleural mesothelioma and are exploring your treatment options, intraoperative photodynamic therapy could be for you. Get connected with current clinical trials to find out if photodynamic therapy is for you.