Written by: Devin Golden
Mesothelioma Photodynamic Therapy
Mesothelioma photodynamic therapy (PDT) uses light to kill cancerous mesothelial cells. This emerging treatment can improve survival and pairs well with surgery and other therapies, like virotherapy and immunotherapy.
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Important Facts About Mesothelioma Photodynamic Therapy
- Photodynamic therapy sends a photosensitive drug into the tumor site, where mesothelioma cells absorb the agent.
- Doctors aim a laser light attached to an endoscope at the tumors. This light causes the photosensitive drug to release a molecule that kills the cancer cell.
- PDT can cause a few temporary side effects, most notably skin and eye sensitivity to natural and artificial light.
- Photodynamic therapy works with surgery, virotherapy and other types of mesothelioma treatment
What Is Photodynamic Therapy?
Photodynamic therapy is an alternative cancer treatment. It uses special photosensitive drugs, or photosensitizers, to absorb light and kill cancer cells. Photodynamic therapy has a few names:
- Photoradiation therapy
Using Laser Light to Treat Mesothelioma
Doctors usually insert a photosensitizing agent, or drug, into the bloodstream. These agents are intended to be absorbed by the fast-spreading mesothelioma cells.
Once absorbed, the agents are sensitive to light. Doctors shine a laser light on the area where tumors reside. This activates the drugs, which release a special chemical that kills cancer cells from within.
Doctors use a thin fiber-optic filament to deliver the laser light at the tumors. The filament passes through an endoscope, which is a tool utilized to look inside the body during camera-assisted surgeries and biopsies.
The time between the patient receiving the drug and undergoing the light therapy is called the drug-to-light interval. According to the National Cancer Institute, the therapy usually needs 1-3 days to:
Travel through the bloodstream
Reach the tumor site
Be absorbed by the cells
PDT also kills blood vessels that supply mesothelioma cells with nutrients. This leads to “hypoxia,” or cell death.
Mesothelioma tumors inspire the creation of new blood vessels, a process called vascular endothelial growth factor (VEGF). PDT can act as an anti-VEGF therapy.
Photofrin is the primary photosensitive drug for mesothelioma. It’s also called “porfimer sodium.” Photofrin has no effect on patients until it’s light-activated, which reduces side effects.
Photofrin is not FDA-approved for mesothelioma. It is approved for intravenous use in other cancers.
Benefits of Photodynamic Therapy for Mesothelioma
Photodynamic therapy is a non-invasive, targeted treatment option. Doctors recognize that cancers like mesothelioma overtake healthy cells and other agents in their path. Specialists try to use this characteristic against the disease.
The targeted approach improves survival and comfort for patients. PDT also makes surgery more effective when used intraoperatively (during surgery).
Improved Survival Times
Photodynamic therapy is a promising treatment option, especially when paired with mesothelioma surgery.
Cases of early stage mesothelioma nearly reached five years for median survival. Epithelioid histology had a median survival of 41 months.
In another study investigating PDT with surgery, the median survival was 36 months for stage 1 and stage 2 patients.
Fewer Side Effects
There are no long-term side effects with photodynamic therapy from clinical trials. The targeted nature of the treatment leaves healthy cells mostly unaffected.
There are some short-term side effects with photodynamic therapy. Healthy cells may absorb some of the photosensitizers, which leaves them susceptible to irritation from light. The National Cancer Institute states these effects can last up to six weeks.
The side effects are:
- Skin and eye sensitivity (burning sensation) to bright artificial light and sunlight
- Skin changes (redness, itchiness, swelling and even blisters)
- Swelling in the treated area
Sunscreen does not protect against these effects. Chances of irritation depends on where doctors inject the photosensitive drug.
How Virotherapy Helps With Photodynamic Therapy
Virotherapy is an emerging therapy for mesothelioma. It involves delivering viruses to attack mesothelioma cells explicitly.
Some forms of virotherapy are “transports” for other therapies, such as photodynamic therapy.
Since the photosensitizer can affect healthy cells, virotherapy delivers the PDT drug just to diseased cells. This method reduces adverse effects from photodynamic therapy, such as healthy cells becoming sensitive or dying due to natural light or medical light.
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Intraoperative Photodynamic Therapy for Mesothelioma
PDT is not effective as a standalone treatment due to the nature of mesothelioma tumors. Their scattered makeup offers a challenge for any nonsurgical therapy to stop or slow the disease’s spread.
Even surgery has challenges, since the microscopic, separate tumors can evade resection. 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.
During intraoperative PDT, doctors apply laser lights directly into the chest cavity to ignite the photosensitizer. This provides direct access to the disease location while surgeons resect the disease through surgery.
Survival From Intraoperative PDT for Mesothelioma
Dr. Joseph Friedberg, a specialist at the University of Maryland Marlene and Stewart Greenbaum Comprehensive Cancer Center, authored a paper on intraoperative PDT. He explained that radical pleurectomy with decortication (P/D) is the preferred operation. This surgery removes the:
- Pleura (where pleural mesothelioma forms)
- Part or all of the diaphragm (muscle beneath the lungs) and pericardium (lining of the heart)
Once the surgery finishes, PDT begins and lasts around one hour. Doctors sew in light detectors into the chest region and monitor the light dosimetry for safety purposes.
Dr. Friedberg and his colleagues conducted a study of radical P/D with PDT. Around 80% of the 14 patients survived for at least four years after surgery, which is astounding.
Dr. Friedberg’s findings suggest capitalizing on the immune response with mesothelioma immunotherapy.
Ongoing Research Involving Mesothelioma Photodynamic Therapy
Roswell Park Cancer Institute, in Buffalo, New York, has multiple studies looking into photodynamic therapy for mesothelioma. The focus includes intraoperative PDT.
During surgery, doctors applied a PDT laser light directly into the tumor site. The researchers compared this method to adjuvant intravenous chemotherapy, a standard option after mesothelioma surgery. The trial was suspended in September 2020 due to the COVID-19 pandemic. It is now back up and running, recruiting up to 102 patients.
In 2018, Roswell Park Cancer Institute opened another trial investigating intraoperative photodynamic therapy for mesothelioma. Doctors plan to administer a photosensitive drug for 3-5 minutes and then intraoperative PDT 1-2 days later.
Sources & Author
- Getting Photodynamic Therapy. American Cancer Society. Retrieved from: https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/radiation/photodynamic-therapy.html. Accessed: 03/25/2021.
- Photodynamic Therapy for Cancer. National Cancer Institute. Retrieved from: https://www.cancer.gov/about-cancer/treatment/types/surgery/photodynamic-fact-sheet. Accessed: 10/10/18.
- Concordia Healthcare Corp Announces First Patients Enrolled In Phase 2 Clinical Trial Using Photodynamic Therapy With PHOTOFRIN(R) For Patients With Mesothelioma. Biospace. Retrieved from: https://www.biospace.com/article/releases/concordia-healthcare-corp-announces-first-patients-enrolled-in-phase-2-clinical-trial-using-photodynamic-therapy-with-photofrin-r-for-patients-with-m/. Accessed: 03/25/2021.
- Phase II Trial of Radical Pleurectomy With or Without Intraoperative PDT for Malignant Pleural Mesothelioma (MPM-PDT). Clinicaltrials.gov. Retrieved from: https://clinicaltrials.gov/ct2/show/NCT02153229. Accessed: 03/31/2021.
- Light Dosimetry for Photodynamic Therapy With Porfimer Sodium in Treating Participants With Malignant Mesothelioma or Non-Small Cell Lung Cancer With Pleural Disease Undergoing Surgery. Clinicaltrials.gov. Retrieved from: https://clinicaltrials.gov/ct2/show/NCT03678350. Accessed: 03/31/2021.
- Radical pleurectomy and photodynamic therapy for malignant pleural mesothelioma. Annals of Cardiothoracic Surgery. Retrieved from: https://www.annalscts.com/article/view/1214/1605. Accessed: 03/31/2021.
- Photodynamic Therapy for Lung Cancer and Malignant Pleural Mesothelioma. Seminars in Oncology. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4272687/. Accessed: 03/31/2021.
- Targeted Photodynamic Virotherapy Armed with a Genetically Encoded Photosensitizer. MOlecular Cancer Therapeutics. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/26625896/. Accessed: 03/31/2021.