Killing Cancer Cells with the Help of Infrared Light – Photoimmunotherapy Killing Cancer Cells with the Help of Infrared Light – Photoimmunotherapy Near-infrared photoimmunotherapy uses an antibody–photoabsorber conjugate that binds to cancer cells. When near-infrared light is applied, the cells swell and then burst, causing the cancer cell to die. Photoimmunotherapy is in clinical trials in patients with inoperable tumors.