There are lots of different kinds of focal therapy, but they all have the same basic principle: using a high dose of energy to kill cancerous cells. Importantly, this energy is highly targeted to avoid side effect-inducing collateral damage.
But it’s the type of ‘high energy’ that differs between treatments – whether it’s temperature, electricity, or even light. Here, we describe a few different types of focal therapy you might come across.
Cryotherapy was the first kind of focal therapy to come on the scene, after it was developed from a whole-gland version of the treatment. The idea is to rapidly cool the cancerous tissue to around -40oC, triggering a kind of extreme hypothermia in the cancer cells, which kills them. Slowly warming up the area and giving it a second blast of cold makes sure the treatment has been effective.
High intensity focused ultrasound (HIFU)
HIFU approaches focal therapy from the opposite end of the spectrum – using high temperatures of over 60oC to kill cancer cells. Heat is generated by high energy sound waves, caused ultrasounds. These sound waves are focused by a transducer, in a similar way to how sunlight can be focused with a magnifying glass to burn a hole in a piece of paper. In this way, the sound waves are precisely targeted to burn just the cancerous areas of the prostate, and leave the healthy tissue untouched.
Irreverisble electroporation (IRE)
IRE doesn’t use a thermal approach. Instead, pulses of electricity create tiny holes in cancer cells, causing them to die. The electricity can be very finely pinpointed, making this method highly accurate and lending to its commercial name: Nanoknife.
The Nanoknife is already widely used for some types of pancreatic cancer, but in prostate cancer, testing has been slower to take off. So far, this treatment isn’t approved for use outside of research.
Here, the cancer-killing energy comes from light. Laser beams are used to activate a light-sensitive drug, in precisely the region where it is needed to kill prostate cancer cells. There are a few light-activated drug options out there, but none have yet been proven safe enough for use outside research.