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Doctors are surprisingly bad at understanding the science of probability

Dr Daniel Morgan, (an associate professor of epidemiology, public health and infectious diseases at the University of Maryland School of Medicine)  has found in his research that many physicians misunderstand test results or think tests are more accurate than they are. Doctors especially fail to grasp how false positives work, which means they make crucial medical decisions — sometimes life-or-death calls — based on incorrect assumptions that patients have ailments that they probably don’t. “When we do this without understanding the science of risk and probability, we unacceptably increase the chances of making the wrong choice.”

In one study, gynecologists estimated that a woman whose mammogram was positive had a higher than 80 percent chance of having breast cancer; the reality is that her chance is less than 10 percent. Of course, women who have a positive mammogram often undergo other tests, such as an MRI and a biopsy, which can offer more precision about the presence of cancer. But researchers have found that even after the battery of exams, about 5 of every 1,000 women will have a false-positive result and will be told they have breast cancer when they do not.

The confusion has serious consequences. These women are likely to receive unnecessary treatment — generally some combination of surgery, radiation or chemotherapy, all of which have serious side effects and are stressful and expensive. Switzerland and France, grasping this problem, are halting and reconsidering their mammogram programs. In Switzerland, they’re not screening ahead of time, preferring to manage cases of breast cancer as they’re diagnosed. In France, doctors are letting women decide for themselves whether to have the tests.

Read the full article at the Washington Post.

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What do Dogs and BreastDefense have in Common?

Some biologists think that a target of 99% accuracy for any cancer screen is unattainable.

It seems that SignPost is not alone in this pursuit.

According to a company called BioScent Dx, dogs are able to smell minute changes in a human bio-markers including hormones, proteins and other organic compounds. This has lead to dogs being trained to aid in the monitoring of conditions such as diabetes, narcolepsy and cancer. BioScent Dx is working on developing a cancer screen for recurrent breast cancer.

Studies have shown that, when trained, dogs can detect cancer from human breath, fecal, and urine samples with up to 99% accuracy.

BreastDefense has determined through initial work that 99% accuracy of breast cancer is attainable.

 

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The Sharks and The Minnows

The wide net of cancer detection is picking up the Sharks – the aggressive tumors – and the Minnows- the non-aggressive tumors.

“We are not seeing enough of the really lethal cancers, and we’re finding too many of the slow moving ones that probably don’t need to be found” says Laura Esserman, a breast cancer surgeon at the University of California, San Francisco.

Early detection has long been seen as a powerful weapon in the battle against breast cancer. Some experts now see it as a double edged sword.

BreastDefense will be able to solve this problem. BreastDefense will be able to distinguish the Sharks from the Minnows.

The entire article can be found here.

This article was written in 2014. There is still no test to tell the difference between invasive and benign breast cancer. However in the past couple of years big data and biology have intersected to create novel methods of research. The technology is advancing rapidly.