Ultraviolet Blood Irradiation uses ultraviolet energy which is put into the body by way of IV to oxygenate the blood and is theorized to kill microbes in the body, among other things. It has a long history and is now being reclaimed as a treatment for many different diseases due to its purported physiological effects.
The Issels Immuno-Oncology website states:
“Ultraviolet Blood Irradiation increases venous oxygen in patients with depressed blood oxygen values, enhances the resistance to acute and chronic viral and bacterial infections, has rapid detoxifying and anti-inflammatory effects and has a regulatory influence on the autonomic nervous system. The activation of the metabolism can last up to 42 weeks after completion of treatment.” 
In one study, it was found that with appropriate doses, Ultraviolet Blood Irradiation may selectively inactivate microbes while maintaining the viability of cells and has been shown to promote wound healing. UVC is also found to be less damaging to tissue than UVB. Even though UVC may produce DNA damage in mammalian cells, it can be rapidly repaired by DNA repair enzymes. 
For cancer patients, this may mean, among other things, a possible better way of fighting off microbes without extensive damage to non-cancerous cells.
There are two means for administering ultraviolet blood irradiation:
The first treatment involves the taking of a certain amount of blood and placing it in a specialized container with a small amount of anticoagulant. It is then put through an irradiation chamber where it is exposed to an appropriate level of ultraviolet energy, before being returned to the body. The treatment takes about 30 minutes, and the number of repeat treatments will depend on the individual needs of each patient.
The second is a leukapheresis-based procedure which is FDA approved for cutaneous T-cell lymphoma.