Study lacks detail about medical imaging cancer risks

In the spring, a young neighbor's fancy lightly turns to thoughts of a green lawn and budding rose bushes. He treats his yard with great care, watering with precision, pruning at the most opportune time, and spreading an exact amount of fertilizer evenly. He is rewarded each spring with the most beautiful yard on the block. I haven't thought to ask him how he knows the definitive measurements, formulas, and timing for his little plot of utopia, but it's clear he has it down pat.

Precision is paramount in the medical imaging field as well, as highlighted by a fresh study by the American College of Radiology. But there seems to be a bit of hyperbole thrown in the mix that just doesn't pass the smell test.

As the members of the ACR's Blue Ribbon Panel on Radiation Dose in Medicine acknowledge, medical imaging has brought about dramatic and positive changes for health care. Where once patients were subjected to "exploratory surgery," the practice has been scaled back considerably in favor of physicians using various modalities to quickly and painlessly detail a malady and begin treatment.

There's a huge debate about whether the increased use of radiation will, in the long term, significantly increase incidences of cancer. According to the Blue Ribbon Panel, "the presumption is that it will."

The panelists write that in 1987 medical imaging contributed less than 15% of the average radiation exposure to the US population, noting that the majority of exposure came from radon and other natural sources. With more frequent use of diagnostic imaging at relatively higher doses, the authors say the percentage "has most likely increased."

Presumption? Most likely? That's not a lot of hard science from hard scientists.

The ACR cites a report by the National Council on Radiation Protection and Measurements that the amount of radiation US patients receive through medical imaging has increased fivefold since 1980.

"Although there are currently no data showing that high-dose medical diagnostic studies such as computed tomography and nuclear medicine have actually increased the incidence of cancer, a 2004 study (using survey data from 1991 to 1996) suggested that medical exposure might be responsible for approximately 1% of the cancer in the United States," the panel wrote.

There is a certain logic to their conclusion: Put too much weed-killer on the lawn and the grass will die. But we're talking low-dose here. To accept the presumption, I'd have to also believe that every tablet of ibuprofen I take moves me one step closer to destroying my liver. I run a greater risk of contracting skin cancer from walking across the street and chatting up the green-thumb neighbor every day at high noon, and the reason is there's greater risk from the sun than there is from the CT scanner at the local hospital.

Manufacturers have, understandably, taken a defensive approach. The Medical Imaging and Technology Alliance, which is part of the National Electrical Manufacturers Association, cites Federal Drug Administration data on a less-than 0.05% risk of contracting cancer from CT, for example.

The group also notes that technological advances over the same two decades of explosive growth that the Blue Ribbon Panel cites have actually led to a reduced radiation exposure of 20% to 75%.

Emory University and Massachusetts General Hospital research was revealed at last month's meeting of the American Roentgen Ray Society that shows solid results on 64-slice CT using just 20% of the standard CT dose.

The ACR panel's report raises a real concern—patient safety. But they do it in such an alarming and surprisingly unscientific way that it causes some disbelief. It smacks of the media hype a few years ago about cell phones causing brain cancer.

All parties agree the medical imaging industry needs to operate with the utmost attention to safety for both the patient and technician. The ACR argues for training and dosage standards; again, no one would disagree. But let's keep in mind that what has allowed the exponential growth of the industry is that precise mix of technology and personal care.

Dan Anderson
Editorial Director