ACADEMY PUBLIC POLICIES

Why Cancer Develops?

The wife of a patient of mine with lung cancer asked to speak to me in private. A wife and mother, M.  was battling to keep her husband alive and her family intact. She was experiencing sleepless nights and needed answers to a number of burning questions. M. was trying to come to terms with what could have caused her husband’s cancer at the early age of forty-six. He was a virile man, an outdoorsman and construction worker, the kind of person everyone likes instantly because of his easygoing manner and giving smile.

He was also a three-pack-a-day-cigarette smoker, having smoked from age thirteen until he quit at age thirty-nine. M. knew that cigarettes contributed to his cancer but wondered if the dusts he inhaled at work for many years could have also played a role. She was also concerned that lung cancer could run in families, and if so, whether her little boy would be at risk for cancer later in his life. As her strength rose above her sadness, M. wiped away her tears and said, “That’s it.

I’m sorry to burden you. But I need to know. I just need to know.” When you or someone you love is diagnosed with cancer, there is a compelling human need to know why the cancer occurred.

Those affected by cancer naturally ask, “Why me?” “How did this happen?” “Why did I get cancer?”

 People have different opinions and beliefs about why they developed the disease. Some think they were destined to develop it because many of their relatives had cancer: “It’s in the family.” Some wonder if their diet was too high in sugar or fat. Others are convinced that unhealthy workplaces are at fault. Some people blame themselves for using tobacco products. And still others wonder about radiation exposures, alcohol, infections, other health problems, medications, stress, or impurities in the water we drink, food we eat, and air we breathe.

Who is right? Actually, everyone is right, but to a degree. Each cancer is caused by a unique mixture of factors that collectively resulted in its occurrence. Each factor exerted a certain pressure on the cells of the body that led to that cancer. Some cancers are caused by one strong factor that exerts tremendous force, like a knockout blow to a prizefighter.

Others are caused by many factors that each exerts only minor force, like hitting a prizefighter with a hundred little jabs before finally knocking him out.

It is easier to identify the root causes of cancer when only one or two factors are at work compared with a variety of factors. Cancers that have a strong genetic basis, the “inherited cancers,” are much better understood than are the “sporadic cancers,” which affect those without a strong family history of cancer.

An example of a single strong risk factor is in individuals who have a disease called FAP, or familial adenomatous polyposis. Those with FAP develop hundreds or even thousands of polyps in their colons beginning in childhood and have a nearly 100 percent chance of developing colon cancer by age fifty. They have inherited a genetic predisposition to cancer caused by an abnormality in a gene called APC that exists in their family’s DNA. Those with FAP are counseled about why their genetic mutation leads to cancer and are advised that removal of the colon and rectum, when the polyps become too numerous to remove during suveillance, will save their lives; cancer can be averted. The scientific basis of this cancer is well understood, so patients can be told why the cancer developed.

On the other hand, a healthy man without a strong family history of cancer cannot be told with certainty why he developed prostate cancer.

Numerous factors may have contributed to it, including a diet high in animal fat and red meat but low in fruits and vegetables; repeated infections of the prostate; older age; and an African American heritage.

Prostate cancer affects more than two hundred thousand American men every year, the vast majority of them over age sixty. It strikes one in every six men, suggesting that the tendency of the prostate gland to develop areas of cancer may be a by-product of living to an advanced age. Clearly, the exact reasons why prostate cancer occurs are not well understood. There is no single gene, no toxic link where blame can be laid. Yet this is the usual situation for most cancer patients.

Most people diagnosed with cancer receive no satisfying answer to the question “Why did I get cancer?” Many agonize over the cause of their cancer and wrack their brains to figure out what could have brought it on. I tell them to go easy on themselves, for several reasons. First, most of the common cancers take decades to develop; one would have to examine all their exposures over a twenty-to-thirty-year period to figure out which ones contributed to cancer. Second, no one can lead a perfect life, eat a perfect diet, or be born with perfect genes.

Certainly, tobacco products, diets full of empty calories, and lifestyles lacking exercise are not optimal for human health and do contribute to cancer; indeed, a cancer diagnosis should provide a strong motivation to change these poor habits. Third, as explained above, the vast majority of cancers occur for unknown reasons. Even if every known, controllable risk factor was minimized, cancer might still occur. This is because cancer is a very complicated disease; there are few simple answers. It will take more time and more research to understand completely why we get cancer.

Fortunately, many brilliant people have dedicated themselves to unraveling the mysteries of cancer. In laboratories and scientific institutions around the world, our genes are being probed and our environment is being analyzed. Astounding progress has been made. Our highly sophisticated understanding of cancer today was galvanized in 1953 by the discovery of the structure of DNA as a double helix by James Watson and Francis Crick. Because cancer is ultimately a disease of DNA, a clear picture of DNA was needed before the field of cancer research could progress. Watson and Crick’s seminal finding was to biology what the discovery of digital circuitry was to the development of computers.

The ensuing fifty years has seen an avalanche of knowledge about how our bodies work and what goes wrong when cancer sets in. New cancer fighting therapies are rapidly being developed based on this knowledge.

Even so, we are just beginning to appreciate the intricacies of cancer’s initiation in any one of us. It has become evident only in the past few years that most cancers arise through a complex interplay between our DNA and the environment in which we live. When the environment interacts with DNA in a harmful way, DNA can become damaged. If the damage is not repaired, then DNA becomes permanently altered and is said to have undergone mutation. Over many years, numerous mutations accumulate in cells destined to become cancerous. These mutations to DNA drive cancer’s development. Cancer results when “good” DNA goes “bad.” Cancer arises because a part of the normal or good DNA that we are born with is changed by mutations and becomes bad. Bad DNA imparts to a cell the properties of unlimited growth, ability to spread, and inability to die-the defining traits of cancer.

 1. But  what causes these harmful DNA alterations to arise? Aren’t the things that cause mutations in DNA the true causes of cancer? Indeed, they are.

Two main categories of factors determine whether DNA will undergo mutation: (1) our genetic makeup, or the DNA we are born with; and (2) our exposures, which include diet, lifestyle, and environment, or what we do to our DNA. These two factors are commonly called nature and nurture, respectively.

Cancer is no less determined by a combination of nature and nurture than are most other illnesses. Like so many human ailments, cancer often results from harmful interactions between our body and the environment. Diabetes, high blood pressure, and high cholesterol are common medical problems often brought on by a combination of poor dietary choices, excess body weight, and an underlying predisposition to these conditions. This interaction between nature and nurture is plainly summarized in a statement about the causes of multiple sclerosis (MS) in a medical textbook: “MS [is] likely triggered by an environmental exposure in a genetically susceptible host.” In other words, some environmental stimulus can cause MS, but mainly in people whose DNA is susceptible to that stimulus. The same can be said of cancer.

It is the great hope and challenge of the next decade that cancer researchers will better identify both the environmental factors and the genes that lead to the different cancers. I also indicate how this information may benefit you if you already have cancer. The discussion begins with the focal point of cancer initiation, DNA.