Photoimmunotherapy aims to destroy cancer cells while leaving healthy cells unharmed.
When Kerstin Stenson, MD, describes the innovative technique she is helping develop to fight cancer, it seems like she’s describing a Tom Clancy military espionage novel.
Stenson is treating patients with photoimmunotherapy, PIT for short, an experimental technique that combines the immune system’s ability to target cancer cells precisely with laser energy’s ability to destroy those cells. Like a high-tech weapon in a Clancy thriller, PIT delivers extremely precise, lethal payloads with minimum collateral damage.
“This treatment is so unique and promising because its cancer cell-killing power is so selective and immediate,” says Stenson, director of Rush University Medical Center’s Head and Neck Cancer Program. “It really is just like a guided missile.”
Cold war spy novels like Clancy’s that celebrate military technology aren’t Stenson’s first fiction choice, but she appreciates their parallels to her work when it comes to developing new weapons to fight an old enemy. Just as a hero needs to defeat the bad guys while also saving the hostages, PIT meets the fundamental challenge in defeating cancer: balancing the ability to destroy cancer cells while limiting the damage to surrounding tissue.
Photoimmunotherapy expands upon an existing therapy called photodynamic therapy, a two-step process that starts with a patient being injected with a specialized drug, called a photosensitizer, that’s designed to accumulate in and near a cancerous tumor. Then doctors beam specific wavelengths of light at the tumor, causing the absorbed photosensitizer to produce a form of oxygen which kills nearby cells.
But in photoimmunotherapy, the photosensitizer is combined with a laboratory-produced antibody — called a monoclonal antibody — that specifically targets and binds with receptors found only on the surface of head and neck cancer cells. Administered intravenously, the photosensitizer/antibody combination — referred to as a “payload drug” — circulates throughout the patient’s body, but only latches onto head and neck cancer cells.
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