risk-game

This may be a touchy issue, but I thought I would weigh in on the news that seemed to be somewhat ubiquitous regarding Angelina Jolie and her prophylactic mastectomy. She wrote an article in the NY Times about it entitled My Medical Choice. It’s a personal choice and Jamie Lee Curtis seemed to praise her brave steps and quiet dignity in a Huffington Post article entitled Freedom of Choice, Freedom of Privacy. I can respect that, Angelina’s choice and some opinion on her bravery and dignity. I do, however, worry about what kind of message this sends. Yes, it is good to have a choice for health and longevity, but it’s not just a matter of statistics (but I will touch on the statistics here too). Being ‘at risk’ is not a disease. Even genetic or hereditary indicators does not account for exceptional cases where a gene is present but causes no disease. The science on this is all so very new in the last decade or two and I worry that decisions are being made based on incomplete science and misinterpreted statistics. There are social psychology issues involved here too in such so-called risk reduction surgery. My big concern with a high profile story like this is that it starts a wave of actions without thinking fully and just following a celebrity, who is really just a person like me, you or anybody, making personal decisions based on their perspective and private reasons. That’s something to think about.

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I’d like to discuss statistics now. Do you know the difference between a single event probability and  a conditional probability? Is there a difference between the chances of something happening versus the frequency of occurrence of that same something happening? If you don’t know the answers to these questions then you are not alone. The medical community uses statistics to inform their patients, but your doctor probably does not really understand the statistics. He or She is a physician, not a mathematician, right? I’ll trust my doctor any day to prescribe an antibiotic for me, but to compute my odds for survival given a serious disease – no way! The doctors get these statistics from consensus in the literature. I will take the doctors numbers and then go investigate them. Let’s take the case of Angelina Jolie. In her article she says (because she tested positive for the BRCA1 gene):

“My doctors estimated that I had an 87 percent risk of breast cancer and a 50 percent risk of ovarian cancer, although the risk is different in the case of each woman. Only a fraction of breast cancers result from an inherited gene mutation. Those with a defect in BRCA1 have a 65 percent risk of getting it, on average. Once I knew that this was my reality, I decided to be proactive and to minimize the risk as much I could. I made a decision to have a preventative double mastectomy. I started with the breasts, as my risk of breast cancer is higher than my risk of ovarian cancer, and the surgery is more complex.”

She says later in the article:

“I wanted to write this to tell other women that the decision to have a mastectomy was not easy. But it is one I am very happy that I made. My chances of developing breast cancer have dropped from 87 percent to under 5 percent. I can tell my children that they don’t need to fear they will lose me to breast cancer.”

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Was the choice Angelina Jolie made the correct one? Personal feelings aside (and that’s a self analyzing choice), it is hard to say and depends how you look at the statistics. Lets look at the absolute and relative probability. The absolute probability reduction says from 5 to 1 in 100, which means a risk reduction of 4 in 100, or 4% reduction in risk. On the other hand, the relative probability says 4 saved out of 5, or 80% reduction in risk. That is, the relative risk reduction is the absolute risk reduction (4/100) divided by the patients who die without treatment (5/100). Do the math (4/5=0.80). Another way of saying all this is the Number Needed to Treat (NNT). The number of women who undergo prophylactic mastectomy to save one life is 25 because 4 in 100 (1 in 25) is prevented by such surgery.

What can we really say about the statistical numbers presented by Angelina Jolie? She was speaking from a relative probability perspective (I think), going from 87% to 5% and reducing her chances of cancer by 82%. In terms of absolute probability it’s still only 4-5% risk reduction at best. The number needed to treat is important because it builds the population – 1 life saved in 25. What does it mean? It means that the life of one woman was saved, but the other 24 had no benefit from the mastectomy. Most high risk women don’t die of breast cancer, even though they keep their breasts, and few die of breast cancer either after having their breasts removed. I have considered the high risk category for discussion here like Angelina announced as a point for discussion, not judgement. I’d like to take the opportunity to extend good wishes for Angelina, Brad, their children & extended family during this time. Take care of each other!

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My personal advice – Make YOUR own choice and know the numbers to make an informed one on Risk Reduction. Don’t just know the numbers, but know what they mean too! Remember there is absolute risk reduction, relative risk reduction and numbers needed to treat. We also have the single event and conditional probabilities too. It’s a head full to be sure, but not such an egghead thing when your life is on the line and body parts are involved. Kind of a serious post from me with a message. It’s not personal, it’s just something I wanted to say in a logical way, but I can’t help thinking (after writing this) that it has affected me in an emotional way too.

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