Monday, April 21, 2008

ES Prognosis (The Median Is Not the Message)

Above is a chart reviewing the "prognostic literature" on epithelioid sarcoma. The chart and the papers its data came from may come in handy for those trying to figure out how they are going to survive this disease, and what factors may influence that survival.

But before you enlarge the chart, read "The Median is not the Message," a short essay by the late Harvard evolutionary biologist Stephen Jay Gould. It is, he writes, "a personal story of statistics, properly interpreted, as profoundly nurturant and life-giving..." Gould was diagnosed with abdominal mesothelioma. He read up on the disease and found a median survival time of 8 months -- he was crushed at first, and then he started thinking.

The problem may be briefly stated: What does "median mortality of eight months" signify in our vernacular? I suspect that most people, without training in statistics, would read such a statement as "I will probably be dead in eight months" -- the very conclusion that must be avoided, since it isn't so, and since attitude matters so much.
Gould lived for 20 years after his treatment, and died of something else entirely. So much for that eight-month median.

The chart here offers no context, and it's important to realize that the results are skewed in all sorts of ways: some of the data is too old, some of the groups of patients were much sicker than others, some of the groups are too small... Even within a given series (group of patients), results can vary hugely by the type of treatment (wide surgery before mets). 

I have to laugh a little here, as I encourage people to not misread the data and become too discouraged, because shortly after my own diagnosis, I skimmed a bunch of prognostic studies myself and completely misread the data -- in my favor. My erroneous optimism was quickly checked by reality, but my strong initial sense that I could and would survive five years, ten years, and possibly many more was a huge help in the early days of adapting to the illness. I should say that this kind of optimism is appropriate to many people diagnosed with epithelioid sarcoma; what I didn't realize then was that my prognosis was worse than the average ES patient's because of the central ("proximal," in the lingo) location of my tumor, the likelihood that it had already spread locally, and the involvement of my lymph nodes. I'll elaborate more on positive and negative prognostic factors in a future post. 

But I still believe strongly in my initial impulse: The key is to get the right treatment and survive right now. Even if the disease boomerangs viciously back in five years -- one year -- who knows what options will exist then? The science is changing all the time; too slowly, yes, but it is changing. Even since August 2006, when I was diagnosed, several promising trials have launched, and one strong effort (yondelis, or ET-743) has apparently bombed, at least for ES. 

The chart comes from an article in Cancer titled Epithelioid sarcoma: Still an only surgically curable disease.


staggs42 said...

I love this post. Yes, I love statistics arguably more than is socially acceptable, but more than that, I don't think any of us could ever have a moment's peace, much less days of optimism, if we weren't in certain ways underestimating the gravity of, well, everything. Even if everything in one's own immediate family and workplace is utterly rosy, there is all that world news to think upon. It is splendid that you see the bright side of your early misinterpretation of the data.

SG said...

hey! nice to see you here. yeah, denial/misinterpretation is highly protective, particularly so given that most of the life calculations we do focus on are inaccurate in dispiriting ways -- statistics show (heh) that most of us consistently err in assessing how much happiness purchases, relationships, life changes, etc, will bring.