How to Re-interpret Cancer Statistics

In most cases we shouldn’t take a statistic at face value. Let’s look at another statistic for prostate cancer, specifically, that after 50% of the men diagnosed with metastatic prostate cancer will live longer than 30 months. This is called the median survivability. Recall that this statistic was computed by tracking a large number of men after they were diagnosed with metastatic prostate cancer. The researchers noted how long it was after the diagnosis that the men died. Although I couldn’t definitely establish the timeline, I think the study ran for 10 years. For our purpose of reinterpreting, let’s just assume it ran for ten years.

Let’s reinterpret the statistic so it is tailored specifically to my case. First, my metastases were detected very early, well before bone pain. The study includes men whose first detection was after bone pain set in. Their disease had progressed much further before it was caught. If all the men had been diagnosed as early as I was, the overall median survivability would be significantly longer. So when I think about that 30 months, I should probably add a year or two. How much to add is something to discuss with my oncologist.

Second, I was relatively young at 56 and in good health, when I was diagnosed. There are men in the study who were much older and in poor health. If all the men in the study had been of my age and health, that 30 month median survivability would be longer.

Third, a negative, my cancer had a Gleason score 8 and is considered aggressive. There had to be a lot of men in the study with lower Gleason scores. If the study had men only with my Gleason score, that 30 months would be less.

Fourth, I responded extremely well to hormone therapy, which is not true for everyone else. My median survivability should be increased past 30 months.

Fifth, the study started ten years ago. That means a bunch of the people were treated using approaches that were 5-10 years behind what is done now. For prostate cancer that’s very significant. In the past ten years many new drugs have been approved that have significant impacts on survivability. And there are more on the horizon. Median survivability for me should be higher than 30 months.

My oncologist and I discussed all these factors trying to come up with a better estimate for my median survivability. We couldn’t do this right away, though. We needed time to see just how aggressive my cancer really was and how well I responded longer term to hormone therapy. That process took several months. Once that was done he decided that on the most conservative side I should replace increase my median survivability to 36 months. In terms of what he thought most likely to happen, he said I should increase it to 60 months! On the optimistic side he felt 84 months or longer was reasonable, based on all the new drugs in the pipeline.

Always keep in mind that with any statistic, it probably needs to be reinterpreted to better fit the individual in question. The raw data said a median survivability of 30 months. Reinterpreting that statistic to better fit me suggested my median survivability was twice as long!