Second only to heart disease, cancer remains one of our major killers. At great cost in dollars, loss of function, and distressed lives, over a million US citizens deal each year with less than terminal effects of cancer too. Based on the latest available American Cancer Society statistics, about 41% of the population will get cancer (besides relatively benign skin lesions) and 22% of us will die from it. If one receives a cancer diagnosis, concern is legitimate: even after hundreds of billions spent on research to combat this type of illness, 35% of those who develop significant forms of cancer (that is, excluding basal cell or squamous skin lesions) will die from it.
Yet, though in many cases there was nothing that could have been done to avoid this disease, often we need not be merely the victims of fate when it comes to cancer risk. In terms of the averages, there are things people can do to decrease their chances of a cancer diagnosis or of having cancer be what kills us.
Proactive measures we can take include:
The above tried and true suggestions have been around for awhile. A couple others are less certain to be efficacious. There is some evidence that (besides their causing increased skin cancer risk) a lot of exposure to ultraviolet light or x-rays can heighten our chances of getting brain and lung cancers. Some physicians also believe that a diet that contains a lot of processed sugar, for instance from pastries or sodas, or processed flour, as in white bread, can put us at greater risk of 
getting cancer. So, to be on the safe side, we might wish to avoid much processed food overall, limit x-rays to those essential for evaluating our conditions, and have minimal reception of ultraviolet light, instead protecting ourselves with long pants and shirts, wide-brimmed sunhats, and plenty of sunscreen if we need to be outside during the hours when solar radiation would be strongest.
In recent years, a hypothesis has been developed that many cancers are associated with inflammation and increased blood coagulation in the body. Findings support the idea that anti-inflammatory medications or supplements and/or blood thinners may be beneficial not merely in lowering our risks of heart attacks but also for preventing or lessening the progression of cancers. My experience is not statistically valid, yet anecdotally I note a history of about one or two skin cancer lesions on my face, back, or arms every couple years before I began taking a low-dose (81 mg) aspirin tablet daily. The reduction in incidence has been about 80-90% following this one measure, and for several years there have been no further cancers observed in my dermatology exams.
Other commonly available anticoagulants or blood thinners include: Ibuprofen, garlic powder, Vitamin E, Omega-3 fish oil, and ginger powder.
Cautions are appropriate, however, regarding the taking of aspirin or other such circulation enhancers. They can have unintended side-effects and may interact with prescription medications. There is for a few patients a real danger from taking even small extra amounts of these substances. One can wind up getting too much blood thinning without realizing it. For instance, recently I was working in the yard and scratched an arm a little on a thorny branch. The bleeding was more significant than warranted by the small abrasions. I checked online about other sources of blood-thinning than my daily aspirin and was surprised to discover that a habit of adding garlic and ginger powder to some of my foods may have more than doubled the anti-coagulation effects from taking the daily low-dose aspirin.
Accidentally overdoing our blood-thinning can potentially lead to more serious developments, especially if one is in addition taking a prescribed blood-thinner like Coumadin. Naturally, alcoholic beverages can have such an effect too. Thus it may be best to err on the side of too little in the blood-thinning supplements one takes. Otherwise, tiny internal bleeding events, as from a minor fall, getting bruised while working with tools, etc., might lead to near or actual emergencies. In and of themselves there is a small but not negligible risk from too much ingestion of aspirin, garlic powder, ginger, almonds, tumeric, honey, cayenne pepper, or vinegar and other such anti-coagulants. Medical outcomes might include stomach lining or intestinal bleeding and brain hemorrhaging. With this in mind, some recommend that rather than taking low-dose aspirin daily, we might do so every other day, a balance between the benefits in terms of lowered heart disease and cancer risk and the downside hazard of dangerous internal bleeding.
Lately, there has been interesting research using existing remedies helpful for other purposes. An intriguing set of studies shows, in lab animals at least, that a medication effective against pin-worm parasites in humans, mebendazole, appears to prevent cancer development. Human trials have not yet been done. However, mice deliberately implanted with cancer cells in their brains, a circumstance that normally would have led to full-blown cancerous tumors, the medulloblastomas did not develop after they had gotten mebendazole. Several years down the road, similar treatment for people might become common and could potentially prevent or halt the progression of such malignant tumors as killed my oldest brother in 1990 and a cousin in 2016.
Even at the current level of cancer research, measures mentioned in this essay can probably on average cut by 50% or more one's chances of dying from cancer. Besides, if we get more exercise, lower stress, have a bit less inflammation, and eat more healthily, we might also really enjoy our days, a great bonus.