Ten years ago on June 25, 2008, I was diagnosed with colon cancer. My grandmother passed away the night before. She was just two weeks shy of her 96 th birthday. I had planned to spend it with her. Instead, I re-routed the frequent flier miles I was to use for that visit to a plane ticket for my mother, who had now just lost her own mother, to be with me for my immediate surgery. Needless to say, this was one of the worst days of my life as well as my mother’s. Mortality had reached my beloved grandmother, and in nearly the same instant, had come for me.
After finding a tumor in my colon, following a colonoscopy necessitated by several alarming symptoms that had progressed over five years, the results of the toxicology test on my tumor confirmed its malignance. This shocked my doctor because I had no known risk factors, but I was unsurprised. Though I followed a fairly impeccable vegetarian diet for the preceding 15-20 years full of a plethora of whole food - largely from the influence of my Italian grandmother’s culinary mastery and the stupendous, nutritious peasant cuisine her poor immigrant family grew up eating - I knew that did not necessarily serve as a cancer inoculation. Though I had been a non-smoker my whole life as well as an athlete, I knew that neither of these factors necessarily prevented the diagnosis I ultimately received. Though I had no family history of colon cancer – and scant family history of cancer at all – I still suspected the malignancy. And though every doctor I have seen before or since characterized my cancer as a fluke, I knew it was not.
In the few years preceding my diagnosis, handfuls of friends and acquaintances in my age group had fallen victim to forms of cancer. An old neighbor in her 20s and a dear friend in her 30s had both recently died of the disease. The stories of cancer in friends, coworkers, acquaintances, old classmates and their spouses, and friends of friends accumulated. Anecdotally, I saw cancer incidences rising in lower age groups. I felt that I was noticing more cancer among my peers than in my parents’ and grandparents’ generations before me. As a scientist, I knew my personal observational data was not sufficient for any conclusions, so I waited for possible confirmation. I found it when I learned that melanoma, metastatic breast cancer, and colorectal cancers were all on the rise in young and middle-aged adults. These data fly in the face of the notion that cancer has been increasing mainly because it is an old-age disease and more people in our American population are living longer.
In March of this year, the alarming rise in colorectal cancers in younger populations prompted the American Cancer Society to recommend colon cancer screening start at age 45 instead of 50. As always, the recommendation for protection against colon cancer stresses keeping a healthy lifestyle, which includes plenty of exercise, a wholesome diet, and maintaining a healthy weight. To summarize, our colon cancer prevention plan consists of: 1. The generic “healthy lifestyle” and 2. Regular screenings, which are technically not preventative measures but rather diagnostic measures.
In beautifully crafted public relations rhetoric, the medical establishment has defined diagnostic screenings as secondary prevention, and treatment to manage disease and thwart its exacerbation and recurrence as tertiary prevention. Perhaps two additional levels of disease “prevention” were needed because we are so woefully inadequate at the first. The only real form of prevention – primary prevention in medical jargon – is never contracting the disease.
In truth, the etiology of colon cancer is not well known. Several gene susceptibilities increase risk, but these genes factor into the risk equations for only approximately 5% - 10% of colon cancer diagnoses. That a high fiber diet protects against colon cancer – while a diet rich in meat products does the contrary – is conventional wisdom within the medical community, but scientific support for this premise is actually scarce and inconclusive. Some studies have demonstrated a correlation between exposure to chlorinated byproducts in water, but these too are far from conclusive. New research links exposure to triclosan, an antimicrobial compound found in many household and personal care products, to colon cancer. Triclosan had already been deemed a suspected carcinogen, but this new evidence shows that its mechanism for oncogenesis likely has to do with its disruption of the gut microbiome, reducing necessary and beneficial bacteria in the digestive system. This research then also suggests than any agent, such as an antibiotic or a pesticide, that could affect our intestinal microbiome might, in turn, induce cancer.
But what caused my own cancer? I will never know. I drank gallons and gallons of highly chlorinated municipal tap water during the decade I lived in D.C. I used liquid soap containing triclosan for several years in the 1990s before I decided than antibacterial soap was overkill, and I wanted to reduce the waste from the plastic containers it came in. It could have been anything I’d unknowingly been exposed to in my food, water, or air. It could have been chemicals I’d been exposed to in laboratories in school. (Stupidly, we tended to flout a lot of precautions in our college chemistry labs.) It could have been radioactive materials I might have been exposed to in the neighborhood I grew up in, which was in close proximity to a nuclear reactor. (Of note; the proposed National Academy of Sciences study on cancer risks in communities that house nuclear reactors was halted, citing “prohibitive costs,” so I will probably never have any data one way or the other regarding that potential risk.) It is unlikely my cancer could be attributed to one particular cause; more likely, it was the combination and accumulation of a multitude of factors that can never be fully ascertained, as is the case in most cancer patients.
The one factor that did not directly cause my own cancer is an inherited gene because, technically, we do not know of inherited genes that, in and of themselves, directly cause cancer. More importantly, they are implicated in only a minority of cancers overall - 5%-10% of cases. The increasing rates of cancer incidences over the past four decades (the only time period for which we have incidence data) cannot be explained through inheritance. Neither can the increasing rates of cancer in younger populations. If heritable alleles (the different forms of genes) caused terminal diseases like cancer and had no beneficial effects, evolution and natural selection would favor the decrease in these genes in the population. If these genes were initially a huge contributor to cancers, the genes would have been selected against, and cancers would have been declining in humans over time. That has not occurred. Moreover, in terms of the alleles that confer genetic susceptibility to cancer, like BRCA1 and BRCA2 in the case of breast cancer, the relative risk of a woman with these alleles developing cancer has increased over time. That is, women with those gene variations born before 1940 have only about a 24% risk of developing cancer while women born after 1940 have a 67% risk, which means these genes are not the major component of that cancer risk, but the majority of the risk comes from elsewhere – from something interacting with the genes that has changed over time. With colon cancer, for example, the majority of inherited genetic abnormalities linked to colon cancer produce precancerous colon polyps, but it is estimated that even 95% of precancerous polyps will not form cancer. Consequently, it would appear that there may be some other environmental component prodding these precancerous cells into becoming cancerous. Because of the marked focus on heritable “predispositions” to cancer, it appears we might be missing the fact that even these inherited susceptibilities need exogenous environmental factors to eventually result in cancer.
The complexity of cancer itself and of the variety of factors that contribute to it makes direct cancer causation difficult to pinpoint. Statistics from American Association for Cancer Research suggest that tobacco use contributes to between 30-35% of cancers, with obesity a close second, contributing to about 20-25% of cases. But if you examine this and similar statistical charts on relative contributions to cancer incidence, you will see that they include nebulous contributions like diet, inactivity, and obesity, which, in themselves, have no known mechanism to cause cancer, as well as factors like UV radiation, alcohol, and certain pathogens (like viruses) which are known carcinogens. It does not make logical scientific sense to mix known causes of cancer with susceptibility factors in the same general category of this chart, and it puts into question the soundness of the entire analysis. It obfuscates the complexity of cancer causation by comparing causes and risk factors, as if they are the same. It is like constructing a chart about contributors to flu incidence and including the flu virus at 40%, compromised immune system at 25%, lack of hygiene at 15%, poor diet at 15%, and lack of exercise at 5%. The only factor that actually causes the flu is exposure to the flu virus; all of the others might increase risk and susceptibility. The only factors we know of that actually cause cancer are carcinogens, substances that directly or indirectly cause mutations that disrupt the normal cycle of cell division in our body. These include radiation, naturally occurring and synthetic chemicals, and various pathogens.
In any case, even these questionable charts make clear that the vast majority of cancers are highly preventable. The 2010 report of the President's Cancer Panel noted that there are so few data on the hundreds of thousands of chemicals and toxicants in our society, and we have not quantified, and perhaps will not be able to quantify, the cancer burdens from these toxicants. For example, we assume that our regulatory agencies ensure that we are only exposed to carcinogens at low enough levels to keep us generally safe from disease, but we know in practice, this is often not the case. We also know that some types of chemicals that can cause cancer, like endocrine disruptors, do not necessarily have safe levels, because they are actually more harmful at lower than higher concentrations. We also know that some chemicals that are fairly innocuous alone become carcinogenic agents when in particular mixtures. The cancer burden from all possible mixtures of chemicals, which is what humans are regularly exposed to in their lives, is basically unquantifiable and unknowable. And if we cannot quantify the relative contribution of environmental exposures to cancer incidences, then we really cannot truly quantify the relative contribution of other causes either. The panel concluded that “the true burden of environmentally induced cancer has been grossly underestimated.” Developing nations like China are experiencing surges in cancer rates, which they attribute to exposure to carcinogens from industrial pollution. India, a country with relatively low cancer rates, has seen tremendous increases in places where carcinogenic substances like pesticides abound. In addition, humans are inducing cancer in other wildlife species, largely due to pollution. This evidence lends more support to the conclusion of the President’s Cancer Panel that environmental toxicants may be contributing to far more cases of human cancers than we acknowledge. Furthermore, it lends credence to the fact that most cancers could be preventable if environmental toxicants were removed from the equation.
While overall incidence of cancer has declined a bit in recent years (possibly due to a sharp decrease in tobacco use), and cancer death rates have declined modestly (possibly due to more effective treatments), cancer still affects over 40% of the American population and is the second leading cause of death in the U.S.
Diagnostic tests are a good stopgap measure in the short term to deal with the increasing rates of colon cancer in younger adults; however, given that cancer is largely preventable, our long-term goal should be to implement measures that focus mainly on prevention. Not only do too many people in the United States lack access to affordable medical care, medicine is not without its own contribution to our public health crisis. Certain diagnostic tests themselves, such as X-rays and CT scans, may contribute to excess incidences of cancer. In addition, the enormous environmental resource use in the medical industry, and its waste stream, which includes radioactive chemicals, pharmaceuticals, and plastics, both inevitably contribute to the environmental degradation and pollution that threaten our ecosystems and increase our public health burdens.
Sickness is not the default state of organisms, so we should strive to maintain health and prevent the burden of disease as best we can. Of course we should eat well, exercise, and avoid alcohol and smoking as much as possible. But these measures are not enough. In terms of cancer, prevention should mean focusing on reducing and eliminating the only agents that we know to actually cause cancer – carcinogens. They exist in our food, in our water, in our air, and in our products. Far too many are there merely for profit and convenience, not necessity.
Forty-seven years after President Nixon declared a war on cancer, we still have battles raging all around us. In most cases of cancer, we are no closer to cures. Some doctors are expressly saying that we will never cure cancer, but in the future it will be a chronic, manageable disease. For a supposedly highly advanced society, this solution to cancer falls pathetically short of what should be. For victims of cancer and their friends and family, the thought of living with never- ending cancer treatments along with the anxiety produced by a disease that could always become terminal is horribly unsatisfactory.
We are playing Russian roulette with our lives by not addressing so many of the preventable causes of cancer in our society. The oft repeated metaphor about cancer, “the genes load the gun, the environment pulls the trigger” rings quite false. Our toxic environment is the gun and without that environment, the bullets are useless. We need gun control.
* All statistics about cancer above refer to data in the United States, unless otherwise noted.