What is cancer?

The answer to that question is not as clear as you might think.

A dictionary definition states that cancer is “a malignant and invasive growth or tumor, tending to recur after excision and to metastasize to other sites.”  However, not all growths that are designated as “cancer” behave in that manner.

The determination of whether the word “cancer” is included in the medical name of a growth when it is removed and examined under the microscope was established many decades ago at a time when we knew much less about how such growths behave.  We now know that some growths that have cancer in their name can grow very, very slowly and never metastasize (spread) or cause health problems.  These growths might never have been detected at all without modern diagnostic tools.  If left alone, they would be clinically insignificant.

The linkage of the word “cancer” with these abnormalities can cause psychological distress and in some cases lead patients to seek, and doctors to provide, therapy that may not be necessary.  Our persistent use of the word “cancer” where it is not indicated can therefore result in unnecessary psychological, physical and financial damage.

On the other hand, there is no question that early detection of cancer saves lives, and that detecting and treating aggressive cancers early is playing a major role in the decreasing age-adjusted mortality from cancer.  For example, the US Preventive Services Task Force recently highlighted the value of screening CT scans for cigarette smokers at high risk of lung cancer (http://www.uspreventiveservicestaskforce.org/draftrec.htm).

Many decades of experience, and scientific advances, have improved our ability to link both the microscopic appearance of a growth, and its molecular makeup, with a good or a poor outcome.  This ongoing field of research is helping us figure out which growths should be called cancer and need to be treated, and which can just be monitored without therapy.

It is therefore not surprising that a reassessment is ongoing of what should be called “cancer”.  This is the topic of a recent publication in the Journal of the American Medical Association (http://jama.jamanetwork.com/article.aspx?articleid=1722196) and a recent New York Times editorial  http://well.blogs.nytimes.com/2013/07/29/report-suggests-sweeping-changes-to-cancer-detection-and-treatment/?hp.

New names for growths that are current called cancer but behave in a benign fashion will likely be adopted.  One proposed name is IDLE (Indolent Lesions of Epithelial Origin).

Moving forward, progress against cancer will be dependent on prevention, early detection and better therapy.  It will also be dependent on our ability to know who needs therapy, and who does not.  A more precise use of the word “cancer” will help.

George Weiner, MD
Holden Comprehensive Cancer Center Director