What Statistics Can and Can’t Tell Us

Cancer statistics are helpful for planning purposes and to help compare treatment options. Before getting into those details let’s address what cancer statistics can’t do. That’s the source of a lot of confusion folks have when faced with the statistics.

Let’s get the biggest issue out of the way first. Cancer statistics can’t tell us how long we’ll live. The underlying design of statistical experiments makes it impossible to determine pretty much anything with absolute certainty. That also means statistics can’t tell us for sure if a treatment will work for us. Similarly, statistics can’t tell us if we will or won’t get side effects for certain.

Let’s think about why this is true. Statistical charts and data are created by tracking a large number of people and noting what happens to them, say, after they develop a disease or get a treatment. We can calculate what percentage of folks were still alive at least 5 years after they were diagnosed. For example, a man diagnosed with metastatic prostate cancer has about a 30% chance of living past five years, based on the latest research. At five years he won’t be 30% alive and 70% dead. He’ll either be 100% alive or 100% dead. The statistics can’t tell us which group he’ll be in. It does tell us the odds aren’t good that he’ll make it past five years. That reality may influence his planning, but he fundamentally doesn’t know when he’ll die.

The same holds true when looking at statistics for treatments. They only give us some insight into the chance that the treatment will work, or the chance that we won’t be faced with side effects. Only by taking the treatment will we know what the side effects will be for us as individuals. In my case there was an elective radiological treatment option that I decided to take. I was told by two radiologists, an oncologist, and an urologist that the only side effect from the treatment would be minor fatigue. Unfortunately, I was in a very small minority of patients who reacted very strongly to the radiation, and I had a terrible time. The sad truth is we just don’t know for sure what will happen until we do it. The statistics may give us a hint, even a strong hint, but there are no guarantees.


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