The most difficult questions asked of a doctor are those that begin with the word “why.” Doctors often know what is happening with a patient, but why it is happening is often a mystery. Cancer can be found, defined, treated, and often cured, but the why of it—“Why did it happen?” “Why me?” “Why now?”—is difficult to answer. Some pieces of the answers are known, but there is still much to learn.

It is known that smoking is associated with lung cancer, and that human papilloma virus is associated with cervical cancer. By not smoking, and vaccination for HPV, many cancers can be prevented, but not all. For many common cancers, it is not known how to change lifestyle in order to decrease our risk.

The different components that may contribute to the development of cancer include environmental exposures and genetic predisposition, but most cancers do not have identifiable risk factors identified after they have occurred. In other words, the individual would not have been considered at high risk, yet cancer happened.

Scientists have learned a great deal about how cancer happens. Cancer is a disease of cells which are the building blocks of the body. In each organ system, there are cells that generate replacements.  For example, in blood, a normal person might have 20 million red blood cells, and red cells live about 120 days. Thus, every 4 months, the body makes 20,000,000,000,000 new red cells. The basic process is one cell dividing into two cells, each of which is identical to the “mother” cell.  The critical part that needs to be present is DNA, which is the programming of the cell. DNA dictates the behavior of cells. DNA is a long chain of information that enables a cell to interact with its environment. Each cell starts with the same information, but when a cell divides, the DNA must be copied into each of the “daughter” cells. Sometimes, however, mistakes occur, and the sequence of “coding” in a daughter cell may contain a substitute “letter” or some information may have been lost. These mistakes are random, occurring in individual cells, within the molecules that make up their inner core. The mistakes do not occur because of physical trauma (a bump or a bruise) but sometimes bumps and bruises lead us to find things we didn’t know were there. It is not known whether the use of vitamins, antioxidants, or other supplements has any impact on this process.

It is likely that these mistakes happen often, but that many of the changes in DNA are irrelevant as not all of the information in DNA is necessary to each organ system. Alternatively, a change in the DNA may be lethal to the cell, in which case the cell is recycled and broken down into its components without any impact on the organ or the person. The human body is a very effective recycler. However, sometimes a daughter cell contains a change in the programming that alters how that cell may react to its surroundings, but is neither lethal nor irrelevant. With the passage of time, that cell may divide, creating two daughter cells that contain the same changes, and those two may also divide. In a few years, there may be many cells that contain that particular “mutation.”  It is the acquisition of several mutations in a single cell that may lead to cancer. This usually requires many years for the cancers common in adults such as colon cancer and breast cancer. The first in the sequence of changes in the DNA of the affected organ in an adult may have happened more than 15 years before the cancer was found.

A typical cell in the body is measured in microns. Red cells are roughly seven microns in diameter, and most cells in organs are larger, measuring 10-15 microns. However one micron is one millionth of a meter, and it would take millions of cells to make a group large enough to be felt with fingers.  It is thought that in adult cancers, six or eight mistakes happen that lead to cancer, but they must be the “right” (or wrong) mistakes. Although this does not seem like so many mistakes, the chances that someone will develop cancer are actually quite small. After all, it only takes six numbers to win the lottery….

We cannot do much, based on knowing that it helps, to change the process by which mutations (mistakes) occur. And it is a natural process, and the basis for evolution.

We can control our behavior, both in terms of limiting behaviors that put us at risk (tobacco), getting screening tests such as colonoscopy and mammography, and pursuing a healthier and more active lifestyle. We can look for those rarer people in whose families there are many individuals with cancer and see if they fit the known heritable syndromes. In those families, testing for a marker of greater risk may be possible, and it may be possible to find those within the family whose risk is not as great.

As always, it is better to know and to try to modify our own behavior. We need to control the things that we can!