Coffee enemas have been used throughout history and in different cultures as a way to clean out the colon of debris and harmful pathogens. They were even used by Native American tribes, who used coffee enemas as a way to treat liver difficulties.
One article (1) looked at coffee enemas and the treatment of cancer. They found that many cultures have used coffee enemas in the treatment of cancer, such as the Sumerians, Chinese, Hindus, Romans, Greeks, and the Egyptians. They also found that coffee enemas were used in the US until the 20th Century.
Since then, they have fallen out of the mainstream of medical treatments. Coffee enemas are believed to reduce the incidence of cancer by lessening the number of toxins that get absorbed by the colon. This seems to be how coffee enemas can help in cancer healing.
Source: 1.How to Use Coffee Enemas to Detoxify & Heal from Cancer. https://thetruthaboutcancer.com/coffee-enemas-detoxify-heal-cancer/. Accessed 9/15/16.