I spoke with the one of the scientists at NIH in the USA who was involved in the cancer research and he made it rather clear that 99.9% of cancers will not respond to paracrine-origin IGF-1/GH. Cancerous cells grow by DNA damage that results in cells unresponsiveness to neural transcriptions and endogenous hormones. Another part of this DNA damage in rapidly growing tumors (tumor = mass of these unresponsive cells) is uncontrolled autocrine production of IGF-1.