Thursday, April 03, 2008

Doug Davis and the Risks of CT Scans

Arizona pitcher Doug Davis -- about to miss time due to medical treatments -- has won the admiration, respect and well wishes of his teammates. Putting off thyroid cancer surgery to make a couple of starts in April will do that for you. "When I first heard about it, I'm not going to say I wasn't crying," Davis said. "Of course I was." (Tony DeMarco, NBC Sports).

Doug Davis has thyroid cancer. According to repots, he is suspected of having follicular carcinoma. Generally there are four major types of thyroid cancer (in worsening order of prognosis/seriousness and risk for early mortality from the disease):

1. papillary;
2. follicular;
3. medullary;
4. anaplastic

In Davis' case, his cancer may be related to a familiar propensity to acquire the disease -- two first-order family members have a history of thyroid cancer.

However, papillary and follicular carcinomas are also definitely associated, as an independent risk factor, with radiation to the neck. Brilliant and classical epidemiological work by UCLA medical professor JR Hoffman, et. al., in multiple peer-review accepted scientific publications, have clearly illuminated the fact that as many as 1,000 cases of thyroid cancer are diagnosed each year in the US as a direct result of cervical spine x-rays -- the vast majority of which, over 90-percent estimated in various studies, are medically unnecessary.

When you were a kid, didn’t your mother repeatedly bellow one or both of the following to you: "... stop doing that before you put your eye out!!!" Or: "...get down from there before you break your neck!!!" Doubtless this ubiquitous parental admonishment has advanced the notion that every time your neck hurts due to some minor trauma (or even without history of trauma), you must immediately run to the nearest emergency room and get an X-ray -- who wants to have an undiagnosed broken neck, become a quadriplegic and spend the rest of your life in a wheelchair, aye?

Per standard routine, no self-respecting patient in America, with or without third-party entitlement for payment, is going to consider a learned medical practitioner’s opinion that the X-ray is usually not clinically indicated, based upon the history and clinical examination of the malady. Curiously, there is a large subset of the population that never believes the doctor -- they want the technology instead, "just to be on the safe-side." Right.

Generally, the patient (or their family and friend surrogates) are so adamant to insist on the X-rays, that some emergency departments acquiesce even before the patient is seen and the X-rays are ordered by the triage nurse in advance of the physician’s evaluation -- just to move the process along, satisfy the patient, add to the bill, and open that ER bed to somebody who really needs it.

As an emergency healthcare provider, having been confronted with that situation several thousand times myself, when I am really sure the neck x-ray is a waste of time and somebody’s money, or when especially when the patient is a child (see comment below), I will always offer the x-ray series under the proviso that: a) the patient understands that it is not medically indicated, and b) there is a risk of producing thyroid cancer some time in the future.
It is astonishing how many patients will recant their demand for the neck x-ray.

We’re talking just about neck x-rays and baseball players. The amount of radiation produced by a cervical spine x-ray series is miniscule compared to the total body dose of radiation received by computerized (axial) tomography – CT or CAT scans. One CT scan of the abdomen, for example, is the equivalent radiation of 500 chest x-rays (a chest x-ray is about triple the radiation exposure of a neck x-ray). How often do you hear about professional athletes getting a CT scan (not to be confused with MRI which is believed to be safer but fantastically more expensive)?

Examination by MRI is particularly good for soft tissue, but lousy for bony structures. So, if there is a bonk on the head, if there is a peculiar pain or tenderness with a normal plain x-ray, if there is back pain – CTs are often performed. As an aside, it’s important to recognize that fractures elucidated by CT and not by plain radiography are, by definition, not fractures, per se, at all. The "gold-standard" definition of a fracture - one that is evident by plain radiography.
If every time somebody hurt something and the x-rays were negative a CT scan was performed, we might identify lots of occult fractures for which the management is exactly the same – except the bill is enhanced and the patient has absorbed a load of radiation.

Radiation exposure, by the way, is cumulative over one’s lifetime, so exposure to children is particulary important. Over the course of a lifetime, we are exposed to a wide variety of radiation sources from the sun and our TV sets, for example, in addition to medical radiation.
When the dose is sufficient, accumulated over many years: "there’s your cancer, Madam – it’s your turn to die."

The cause of cancer is multifactorial: hereditary factors, viruses, environmental exposure, chemical exposures, and radiation, all of which have been described in the medical literature. I suspect (and the opinion is shared by many scientists more intimately familiar with the subject than me) that one day there will come a reckoning related to our penchant for CT scans for everything from headache, to sinus disease, to chest pain, to abdominal pain, to suspected kidney stones, and extremity trauma.

In 2002, for example, 60 million CT scans were performed in the US, accounting for 70-percent of medical x-ray exposures. According to a report by the National Academy of Science, a single dose of 10mSv is associated with a lifetime risk of a solid cancer or leukemia (with associated death) of 1 in 1,000. The radiation dose associated with a typical abdominal CT scan is 10-20mSv.

It is particularly problematic when patients undergo multiple CT scans. In one study, it was reported that patients with reecurrent renal colic (kidney stone) commonly experience total radiation exposures of 19.5-153.7mSv.

Physicians requesting CT scans for their patients are often unaware of the associated risks. Studies have reported that only 9-percent of emergency department physicians and only 47-percent of radiologists involved with CT scanning were aware of the increased risk of cancer posed by these studies. Failure to appreciate this risk of radiation exposure has a substantial impact on the process of informed consent.

Yes, hopefully when these tests are obtained, we should like to believe that the benefit outweighs the risk, but too often, especially with multimillion dollar professional athletes, it is clearly not. I wonder, if armed with that information, and Doug Davis strained his neck, while intimately familiar with his family history of thyroid cancer, if he would allow the team doctors to x-ray and/or CT his neck?