This blog entry is devoted to helping you understand some very important terms that will help you look at and understand cancer information such as incidence, deaths, rates, etc. I hope you find this useful and do hope you ask me any questions or make any comments you might have! Why do I think this is important? First of all, statistics are thrown around all the time by people. Depending on the numbers that one uses the information can be very misleading. Frequently, I have noticed people quote cancer statistics incorrectly and make false assumptions and declarations. Secondly, people can easily use statistics to falsely make something less or more serious than it is to try to get you to buy their product or to see things their way. Last but not least, is that understanding a little bit about cancer statistics makes you understand that these numbers are usually rough estimates and not 100% facts.
Incidence vs. prevalence. Incidence is the number of NEW cases of cancer (or anything else) that occurs within a specified period of time (usually a year). Sometimes you might see the incidence as a rate like 1 per 100,000 in 2009. Or you might see incidence displayed as an actual number per year. The rate helps people to see the average risk that they may have/had during that year. While the absolute number helps people to see the volume of people who had cancer during that year. Either way, these numbers can be helpful in determining the new cases of cancer diagnosed in that particular year. So you might compare one year to another to see if the incidence of cancer is going up or going down. Prevalance on the other hand is the actual n umber of people having cancer (or any disease) at a particular point in time. It is the total accumulation of known person with that disease who are alive. What this means is that those who have been cured of the disease or who have dies of the disease are NOT included in these numbers but the ones who have the disease and the new ones who are newly diagnosed are included. The cure rate is usually defined at survival after five years (for better or for worse) and thus those surviving after treatment of five years would not be included in the prevalence figures. However, total numbers of patients with cancer is VERY hard to derive as some don’t seek treatment, etc.
Mortality: This term refers to the number of deaths occurring due to cancer (or a certain disease) within a specified time frame. Health care professionals usually like to report the mortality rate which is the number of deaths per 100,000 people per year. This is useful as people generally like to see if cancer as a whole or certain cancers are killing more or less people from one year to another. Winning the war on cancer may not actually mean eliminating cancer (which is probably not very realistic) but reducing the mortality rate associated with cancer as a whole. Fatality is another related term which indicated the proportion of people who die of cancer and is pretty much absolute…you can’t get any lower than death. This is useful when comparing one cancer to another or cancer in general to let’s say cardiovascular associated deaths (e.g. heart attacks). martality should be used as an outocme measure and not as an indicator of the average risk of acquiring the diesase. Note: mortality is most helpful when looking at a population of peoples while fatality is more useful when assesing individual risk.
Lost life year: Another more complex statistics that is often used is the number of years of quality life that is lost when someone gets cancer. This assumes that we know the total number of average years a healthy person lives and then comparing that to the total of years a person of cancer lives. If they get cured than they may be the same but if they die of the diease then the quality of life years goes down unless they die of the disease very late in life. The later can happen in some cases where treatment is very good.
Ok, well I hope this help a little in terms of assisting you with some terms that are almost always used when looking at cancer statistics. In the next blog I will actually provide some of the world figures for cancer incidence, etc.
As usual, I welcome you to visit my web site for more information and I welcome a discussion either here in this blog or on my site. Thank you…….Dr. C