Doctors and researchers at the Abramson Cancer Center, part of the Perelman School of Medicine at the University of Pennsylvania, have been awarded a grant of $8 million to study the effects of intraoperative photodynamic therapy (PDT) on mesothelioma patients. The Roswell Park Cancer Institute in Buffalo, New York is collaborating in the research effort.
During photodynamic therapy, the patient is administered a light-sensitive drug, which is then activated by red laser light 24 hours later to kill cancerous cells. Light is emitted to the cancerous region during a lung-sparing pleurectomy to remove the mesothelioma tumor.
The grant, awarded by the National Cancer Institute (NCI), is funding a clinical trial and additional research into the effects of photodynamic therapy.
A phase 2 clinical trial will allow researchers at Abramson Cancer Center and Roswell Park to observe a greater sample size of mesothelioma patients. The current trial will recruit up to 102 participants.
Unanswered Questions on PDT
Doctors hope the grant from the NCI will shed more light on some of the responses they’ve seen in patients who have had intraoperative PDT.
There is reason to believe PDT may initiate an immune response in patients. Results from previous studies show that a patient’s immune system may be stimulated by the light therapy and begin attacking mesothelioma cells of its own accord. Dr. Joseph Friedberg, a leading expert in this procedure, noticed this in his patients.
“There is speculation that a photodynamic therapy-initiated immune response may have played a role in these results, but this has not been established,” said Dr. Friedberg in a 2013 issue of Lung Cancer Management.
Photodynamic therapy is also believed to have an effect on the blood vessels surrounding the tumor. Blood vessels may be destroyed when the light activates the photosensitive drug, cutting off a pathway for essential nutrients to the tumor cell.
The grant will also be used to study the relationship between survival and preservation of the lung. Intraoperative PDT has been used in conjunction with the extrapleural pneumonectomy (EPP), which removes the whole lung, and the lung-sparing pleurectomy. However, for reasons not yet clear, patients undergoing the lung-sparing procedure have generally fared better.
The purpose of the NCI’s grant, and the clinical trial underway, is to answer these questions, or at least, lend more evidence on the subject.
“PDT is truly an extraordinarily interesting, customizable and flexible treatment modality.” – Dr. Friedberg
Key Study on Photodynamic Therapy
One of the first studies to demonstrate the immense potential of intraoperative photodynamic therapy was published in the Annals of Thoracic Surgery in 2012. This is one of the foundational studies that the current NCI-funded phase 2 trial is building on.
Interestingly, the median survival of patients in the study was long but progression-free survival wasn’t. Progression-free survival is the time that elapses until the cancer starts to get worse. Patients in this study were somehow able to live longer than the typical relapsed mesothelioma patient.
The authors of the study stated, “The reason for this prolonged survival despite recurrence is not clear but is potentially related to preservation of the lung or some PDT-induced effect, or both.”
The main hypotheses as to why this may have occurred are that sparing the lung allows for better overall health and that PDT stimulates the immune system to fight the disease.
Clearing Up Skepticism
Dr. Joseph Friedberg has faced skepticism about the results of some of his research, but this was expected. In an interview back in 2012, it was reported that he knew the results would be doubted by other researchers in the medical community.
The doubts raised were based on the small size of participants in the study and the length of time from the procedure to when the study was published. This study also wasn’t randomized, an issue the study funded by the NCI grant will avoid.
Friedberg wasn’t daunted, however, knowing further research could confirm his confidence in photodynamic therapy. The recent grant from the National Cancer Institute will allow researchers at Abramson a chance to diminish the doubts of other medical professionals.
In regard to the potential of PDT, Dr. Friedberg has said,
“It is one of the only cancer treatments, along with surgery, that has potential to be curative with a single treatment.”
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