A chemistry professor at UT Arlington and her team have developed a chemical compound using PDT for certain patients with bladder cancer. Dr. Sherri McFarland explained to KERA’s Sam Baker how PDT works.
Interview highlights were lightly edited for clarity.
INTERVIEW HIGHLIGHTS:
How PDT works
It uses molecules that we call photosensitizers, but I also call them photo drugs. The mechanism involves the molecule, the photosensitizers, the light and oxygen, and when these overlap in space and time, we get the potent anti-cancer effect.
How does the patient receives the chemical compound?
It's most often given by I.V. Our drug is delivered directly to the bladder, so that helps in terms of safety and tolerability.
We wait for the tumors to take up the drug selectively and then we insert a fiber-optic directly into the bladder. The light turns on the otherwise non-toxic anti-cancer agent that we call a photo drug.
And in our case, the drug is selectively taken up by the cancer cells in the bladder. This minimizes any oxide toxicity to healthy tissue in the bladder.
Now, before we bring in our light, we rinse the bladder several times with water to ensure that we've cleared all of the other drug that hasn't gone to cancer cells.
When is PDT used for cancer?
It’s used in highly specialized cases of esophageal cancer. Some lung cancers. I mean, it's certainly not standard of care for any type of cancer.
Usually, it's used on patients that have already failed other therapies. And in our case for treating bladder cancer, we're doing something similar. These are patients that have become unresponsive to the standard of care — immunotherapy called BCG.
The recommendation at that point is total bladder removal. Some patients are medically unfit to have that procedure. Others just refuse to have the procedure because it's not without its own complications. We try to treat these patients to give them an option so that they don't have to face complete removal of the bladder.
What made you think PDT might work with bladder cancer at that stage?
A few considerations:
- We certainly needed some strategy that could kill direct cancer cells, but then possibly elicit an immune response that could amplify the effect and is known to have that effect.
- We can personalize the therapy very easily because we can calculate the dose that's required in terms of the photo drug, as well as the light based on the patient's bladder volume.
- It's very selective because we can choose where we shine a light. In our case, we illuminate the entire bladder because our filter drug happens to be selective for bladder tumors.
What do you see as the future for photodynamic therapy?
We're really focused on trying to provide options to cancer patients that have either exhausted all of their other options or there just aren't good options for them.
And so in addition to bladder, we're working in the areas of melanoma, lung glioblastoma, some forms of breast cancer.