It is hard to believe that some cancers miraculously disappear, but it does happen. Over 1,000 case studies document cancer sufferers who experienced spontaneous regression of their tumour. So why does this happen and is it possible to exploit it to benefit cancer patients? The earliest documented case of spontaneous regression was in the late 13th century. A bone sarcoma in Peregrine Laziosi spontaneously disappeared after a severe bacterial infection. In the late 1800s, William Coley observed that inducing a fever could result in tumour regression.