Is there more cancer today?

Roughly 1 in 2 Americans will be diagnosed with cancer at some point in their lives.  Some of us are screened for cancer with what seems like an ever-increasing frequency.  Cancer is one of the most researched and most publicized illnesses.  Some would say that awareness of cancer is at an all time high, and this often raises many questions.  Have humans always gotten cancer?  Is cancer more prevalent now than it was before?  Why do our lives seem so full of cancer now?

A brief history of cancer

Cancer arises when cells in the body lose their ability to regulate cellular division.  When this happens, a cell begins to divide out of control - dividing more and more until there are so many cancer cells that it impedes the normal function of the body.  Cellular division is part of life, and some people argue that cancer is as old as life itself.  In fact, recent evidence suggests that dinosaurs got cancer over 65 million years ago.

We know that cancer in humans has been around for some time as well.  The ancient Egyptians and Greeks both described cancer in their medical writings, but didn't have much in the way of treatment besides amputation.  Yet until the 20th century, cancer was just a blip on the healthcare radar.

In 1971, Richard Nixon and Congress began the effort which is now known as the "War on Cancer."    This was a response to the massive increase in the rate of cancer deaths since the turn of the 20th century.  Money has poured into cancer research and treatment since then, yet despite our best efforts, cancer is still predicted to overtake heart disease as the #1 cause of death among Americans within the next few years.

Why is cancer so prevalent?  If we analyze the rise of cancer in the 20th century, we learn a lot about the American medical system, as well as how cancer works.

Read more after the break.

A disease of modern life

In the late 19th century, the main cause of death was infectious disease: Pneumonia, influenza, tuberculosis, enteritis, diphtheria, and many others. Doctors had yet to understand the concept of germs, and in some cases (such as childbirth) the presence of a doctor's dirty hands was one of the primary sources of harm! With the invention of antiseptic and antibiotic techniques, medicine began to decrease the rate of death due to such diseases, and the life expectancy of US citizens climbed from 50 in the year 1900 to 76 in 1998. 

In the graph below, I've plotted the changes in cause of death from 1900 to 2000.  At the top is infectious diseases - anything caused by a bacterial, viral, or other living pathogenic agent.  For instance, in 1900, the top 3 causes of death were pneumonia/influenza, tuberculosis, and diarrhea (caused by gastric/intestinal diseases).  The solid line in the middle of the graph shows the average life expectancy (the values are displayed on the right axis).  As we became better at curing infectious diseases in the 30's, 40's, and 50's, the life expectancy rose dramatically.  And as the population of the US got older, problems like heart disease and cancer are much more prevalent.

So what caused this rise?  There are two types of factors at play: those that increase the rate of cancer, and those that increase its visibility. Unfortunately, the risk of developing cancer increases dramatically the older one gets.  Cancer is a disease of old age, and as the average age of the population has increased, so to do the rates of cancer.  So, somewhat paradoxically, as we get better at curing other diseases, the rate of cancer increases.

Another reason why cancer is more common is that several cancer-causing lifestyle factors have exploded in the past century, the most notable of which are smoking and obesity.  I will cover this in much more detail in the future (ed: What causes cancer?), so I will just leave a quick fact here - according to the American Cancer Society, smoking and obesity together account for roughly half of all cancer deaths in the US.

Cancer also seems more prevalent because our ability to detect it has increased. It was often the case many years ago that people died of unknown causes, and doctors did not have the tools to properly diagnose cancer as the reason. These days, most people undergo mammograms, pap smears, and PSA testing to screen for common cancers.  This testing has lead to a dramatic increase in the diagnosis of early-stage cancer (side note - some researchers argue that we are actually overdiagnosing early stage cancer).

Another factor is our increased ability to treat cancer - as patients live longer after their diagnosis, there are more people living with the disease and there is more awareness in the rest of the public.  Early diagnosis fits in here as well - in years past, a patient might not be diagnosed with cancer until a very late stage.  With the detection of very early-stage cancers in screening, a person will live a much longer fraction of their life knowing that cancer is present.