Betadine can kill blood borne pathogens but what about cancer cells that are outside body , is betadine toxic to those also ?

Betadine is useful in the destruction of many pathogens outside of the body. Any human cell outside of the body, whether cancerous or not will be killed by the betadine. Superficial Skin cells are typically not affected because the top layer is dead. Betadine is not commonly used in the body because of its high toxicity. Use betadine on external surfaces where there is the possibility of contagion

Cancer cells in blood are not blood borne pathogens. Cancer risk reduction: You can reduce your risk of cancer by adopting healthy habits: Eat a mostly vegetarian diet, avoid alcohol, tobacco and street drugs, avoid excessive exposure to sun, get HPV vaccine, exercise 30 minutes each day, drink enough water so your urine is mostly colorless.