There is no diagnosis that strikes fear like a new diagnosis of cancer. At the same time, our ability to detect early cancers through new and enhanced screening technologies has resulted in more patients than ever receiving a diagnosis of cancer. It therefore seems timely to discuss the biology of cancer, a topic often poorly understood by many.
Cancer begins when a single cell develops a genetic mutation and begins uncontrolled growth. Statistically, 90% of these develop spontaneously, and only 10% of the times are there inherited factors. The initial trigger may be environmental, such as tobacco use or excessive sun exposure, or viral, such as is the case with cervical and certain oral cancers. All of us develop abnormal cells from time to time. Our immune system generally recognizes these cells as foreign and destroys them. It is only when this "immune surveillance" fails, that cancer cells can grow uncontrollably and turn into tumors.
Many tumors are very aggressive, grow rapidly, and are difficult or impossible to treat. These tumors are generally already large by the time they are detected. On the other hand, we now have the ability to diagnose many tumors when they are very tiny, often no larger than the head of a pin. With this newfound ability, we are beginning to realize that not all tumors pose a threat. Some grow so slowly that they will never cause symptoms, some may not grow at all, and some will even spontaneously shrink and disappear.
One of the new great challenges in cancer treatment has become figuring out who needs to be treated and who doesn't, since our treatments are almost invariably associated with significant and often dangerous side effects. For example, mammograms have increased the early detection of breast cancers, and as a result, many women are now cured of breast cancer. However, it is estimated that in the United States, about 70,000 cases of breast cancer per year (representing between a quarter and a third of all diagnosed cases) may not have progressed if left untreated. Similarly, we now have the ability to measure how aggressive the behaviors of prostate cancers are in men. With this new knowledge, the standard of care for non-aggressive tumors has become observation. In these cases, men can be spared the complications of prostate cancer treatment with no change in long term outcomes. Lung cancer is one of the most feared cancers. However, with the advent of lung cancer screening, there are now data to suggest that even with lung cancer, up to 30% of tumors do not progress over time.
Cancer is the second leading cause of death in our country and will likely surpass heart disease to become the leading cause over the next couple of decades. So how do we reconcile this with our new knowledge about the biology of certain cancers? What is needed is a two-pronged approach. Ongoing research and development aimed at continuing the battle to treat and cure cancers is critical. At the same time, we need to direct research to study the natural history of different types of cancers. We are just beginning to scratch the surface in this area of research. We need to improve our screening tests to hone in on the dangerous cancers and avoid the problem of over diagnosis of the cancers that never would have grown to cause illness. Lastly, we need to be certain that we are treating only the cancers that are destined to be a threat to the quality of our lives and our longevity. These are daunting challenges for medical research but critically important for all of us.
Ken Cohen, MD, F.A.C.P., CMO
Evergreen Internal Medicine