Insulin, IGF and cancer risks

Insulin, IGF (insulin-like growth factor) and other growth factors have tendency to stimulate cell division while somewhat blocking programmed cell death that could remove cancerous cells. This in turn makes high insulin activity more likely to stimulate growth of cancers almost through entire body. This is probably main reason why fattening diets get associated with cancers (usually with intestinal or rectal cancers but many other cancers seem also connected).
Also blocking their receptors is not likely to become good method for curing cancer as too much blockade can kill fast due to type of diabetic coma. If insulin receptors were blocked brain couldn't absorb glucose and that's almost like losing blood flow to brain. Within minute people could pass out into coma and if it persist for 5+ minutes in can lead to permanent brain damage. Probably much easier to just eat less to avoid cancers.

Type 2 diabetes that causes high insulin levels is associated with increased colorectal cancer rate. Also those who keep injecting insulin risk with increased chance of colorectal cancers. Same risks could come from physical inactivity, fat around abdominal organs and obesity as they cause type 2 diabetes type high insulin levels.
Authors didn't find relation between non-diabetic obesity and cancer rates when they did  26 year long study on non-diabetic 86 740 women and 46 146 men. In this case they didn't notice extra colorectal cancer rates and other cancers were not mentioned. Their calorie intakes were considered (they were questioned every 2-4 years) but it seemed unrelated to cancers. Insulin is released with the intake of carbohydrates, fats and proteins. 
Difference in diabetic and just fatty diets could be that food increases insulin release temporarily but diabetes keeps free insulin levels constantly high.

Comparison of glargine and insulin effects on cancer. High dose (over 40 U) of glargine caused almost 3 times more cancers than low dose of glargine (20-40 U). More specifically 5,26 vs 1,86 cancer cases per 100 patient years. With high and low insulin doses these 3,1 vs 1,7 cancer cases per 100 patient years. Due to ~13% of glargine users getting high dose and ~46% using high dose of insulin, both drugs tend to have in general similar chances of causing cancer (~2,4 vs 2,6 cases per 100 patient years).  
High insulin activity can increase risk of breast, prostate, colon and thyroid cancers.  

At least IGF can increase risks of melanoma which causes around 75% of skin cancer deaths. IGF can also bind with insulin receptors along with IGF receptors and like insulin IGF seems to stimulate cell growth, division and inhibit programmed cell death. IGF-1 receptor seems to make cells divide while IGF-2 seems to avoid cancers as mutated IGF-2 receptors could be found in cancers.
High IGF-1 levels could increase cancer rates in prostate, bones, genitalia, bladder, central nervous system, lungs, colon and breasts. IGF BP-3 receptors seem to protect against cancers and lower IGF-1 concentration.
People with growth hormone deficiency (Laron syndrome) seems to protect against cancers but growth is often stunted to childlike height (also those with Laron syndrome where younger during comparison). Caloric restriction in mice reduced IGF in bloodstream by 25% and had some slowing effect of bladder cancer.
IGF-II levels seem higher both in cancers and normal tissues among black women compared to whites. Also breast cancers among black women tend to be faster growing and more likely to kill.    

Some breast cancers depend on estrogen receptors and can be slowed with estrogen blockers but those breast cancer cells that don't need estrogen seem to depend on IGF receptors and could possibly be slowed with IGF blockers.

IGF is commonly also released due to effects of growth hormone. IGF and insulin receptors seem similar to each other in structure and the small proteins that form insulin or IGF receptors can randomly combine together and these hybrid receptor bind with IGF and insulin. Insulin receptor mediates glucose entry to cell and both receptors stimulate cell division. Ingesting IGF can increase risk of liver,colon, esophageal, gastric and pancreatic cancer.   
IGF and insulin receptors with many phosphate groups seem to be present in "all" breast cancer case.
IGF receptor blocking drugs are tested for possible chemotherapy use but as they block cell growth they are suspected to also retard growth of children including IGF dependent growth of their brains and heart muscles. Also some cancer cell types may not have IGF receptors. Tumor suppressing IGF receptor types could be solved in water in drank to reach gastrointestinal tumors.