A study of 1,290 patients in the US found that people who received such therapies often refused life-saving care such as chemotherapy or surgery.
Fewer of them survived five years after starting treatment compared to those on standard care, researchers found.
Experts urged patients not to ditch proven cancer medicines.
Oncimmune PLC (LON:ONC) is a leading early cancer detection company. It has pioneered the development of autoantibody assay technologies that have the potential to allow cancer detection up to four years earlier than other methods and can be applied to a wide range of solid tumour types.