Friday, October 30, 2009
To CT or Not CT: A Relevant Question in My Life
A reoccurring theme from neurosurgeons and oncologists we visit is radioactive diagnostic tools, such as computed tomography (CT).
My dad went to the neurologist yesterday in hopes of uncovering the cause of a recent head injury. I've joined the doctor's appointment virtually from Maine by speakerphone (not the first time I've done this). The neurologist, after unsuccessfully opening digital files of previous CT/MRI/angiogram scans, decides to order a follow-up CT scan for my dad.
To get on the same page, I ask what he hopes to learn from another CT. "Perhaps, slow-to-no recovery with respect to the bleeding?"
He says, "it's just a follow-up; no reason to suspect slow-to-no recovery based on my dad's behavior."
Next, I ask: "do you think it's worth the carcinogenic risks that accompany radiation-based tools like CT?"
"There are no risks," he replies.
Then, I inform him that there are studies that suggest this could be the case (I remembered reading Australian journal article recently about the subject). He insists this isn't true. I thank him for his help, and we're off the phone.
This triggered the research bug in me. I decided to look for primary evidence to back-up my claim. At first, I found a wealth of popular media coverage treating the topic (e.g. ABC news, WSJ, US News, etc.). All of these articles, however, referred to a single primary source. So, I downloaded the study by David Brenner published in the New England Journal of Medicine. To my surprise, what I read was not fully reflected in the secondary reports made by ABC, WSJ and US News.
Based on Brenner's study and an online primer by the FDA , here's my summary on the state of research regarding the relationships between CT scans and cancer:
No scientific studies have been performed to demonstrate the direct correlation between CT scans and cancer formation. No studies are currently underway either. Brenner's study applies results from previous studies to draw conclusions about CT scans and cancer-effects. This study is based on large populations (~25,000) of Japanese people exposed to various levels of radiation after the atomic bomb in 1945. A second study is also considered where data on 400,000 nuclear industry workers was analyzed. For both of these groups the average exposure to radiation was between 20 and 40 millisieverts (a measure of radiation concentration). This value corresponds to that of a typical CT scan. In these two populations, this level exposure suggests that the average adult has a 1 in 2000 risk of cancerous side-effects.
Of course, drawing conclusions from these two large events regarding the cancerous effects of CT scans is a bit of a jump. More specifically, there are a lot of unknown variables in there; and thus significant room for uncertainty.
At the end of the day, knowing the details of this study, does not simplify my families CT decision. In fact, it just adds more debris to already muddy water.
So, I'll end this post like I feel: inconclusive, slightly confused and still looking for an answer.