Nancy A. Melville

June 30, 2014

MILAN — Patients with non-Hodgkin's lymphoma who have received 8 or more CT scans have a 2-fold risk for secondary primary malignancies, new research shows.

The malignancies are typically located in regions where the radiation fields of thoracic and abdominal CT scans overlap, effectively doubling the radiation dose, according to the researchers.

"The incidence of secondary-cancer origin from breast, stomach, and liver is higher in patients with more CT scans," according to Sheng Hsuan Chien, MD, and colleagues from the Taipei Veterans General Hospital in Taiwan. "These sites are usually located at the interface or overlapping area and receive a double dose of radiation from 2-CT scans procedures."

The nationwide population-based study evaluated 4874 patients with non-Hodgkin's lymphoma who received curative-intent treatment from January 1997 to December 2010.

Overall, patients had a median of 8 CT scans performed within 1 year of their lymphoma diagnosis.

The risk of developing a secondary primary malignancy was 2 times greater in those who received more than 8 CT scans than in those who received 8 or fewer scans (hazard ratio, 2.23; 95% confidence interval, 1.60 - 3.11; < .001).

The difference remained after correction for propensity scores.

Notably, the risk appeared to be dose-dependant. With each additional CT scan, the risk for a secondary primary malignancy increased 3%.

The researchers identified 180 secondary primary malignancies. Rates of cancer in regions prone to overlapping radiation were higher in patients who received more CT scans.

Table. Secondary Primary Malignancies in Regions Prone to Overlapping Radiation

Cancer Hazard Ratio 95% Confidence Interval P Value
Breast 11.22 1.47–85.64 .02
Stomach 5.22 1.17–23.23 <.03
Liver and biliary tract 2.18 1.00–4.73 .049

 

"Physicians should assess the timing of CT scans more carefully and avoid [the overuse of] CT scans, especially in those with complete remission and a highly curable population," the researchers conclude.

"I don't think the findings can be considered definitive, but the study certainly is provocative and justifies more investigation on this issue," said Brad S. Kahl, MD, Skoronski Chair of Lymphoma Research at the University of Wisconsin School of Medicine and Public Health in Madison, who was not involved in the study.

"Until this abstract, I had not seen any data showing a clear link between radiation exposure from CT scans and second malignancies. It's possible, using larger databases, that this finding could be confirmed or refuted; I think that's going to be the next step — to confirm these findings," he told Medscape Medical News.

The use of CT scans for the surveillance of relapse in lymphoma varies considerably. Dr. Kahl explained that his approach with curable disease is to do 2 CT scans in the first year after treatment, 2 in the second year, and 1 at year 3.

In patients with incurable lymphoma, the number can fluctuate, depending on issues such as length of survival and the type of lymphoma.

 
I certainly do fewer CT scans now than I did 10 years ago.
 

"I certainly do fewer CT scans now than I did 10 years ago, based on a better understanding of radiation exposure issues," Dr. Kahl noted.

"Most people have cut down on the number of scans because of these concerns, but the issue is just how far to cut back. That is a question we're all currently trying to come to grips with," he said.

For one clinician, however, the decision has been made.

James O. Armitage, MD, Joe Shapiro Distinguished Chair of Oncology at the University of Nebraska Medical Center in Lincoln, said he has seen no convincing evidence supporting the use CT imaging in the surveillance of lymphoma patients, and does not use it.

"Our team doesn't do routine surveillance imaging because there's simply no benefit from it," he told Medscape Medical News.

 
We think they are widely overused in the United States.
 

"If the scans resulted in people living longer, they would be worth it, but they don't. And with these types of potential shortcomings, it makes little sense to do them. We think they are widely overused in the United States."

The potential drawbacks extend beyond unnecessary radiation exposure, he added.

"An abnormal reading on a surveillance image is often more likely a false positive, and that can lead to biopsies that don't need to be done, or even worse — therapy for disease that's not even there."

For surveillance, Dr. Armitage and his team rely mainly on patient reports of symptoms, physical exams, and lab work. He speculated that CT imaging, in addition to being a matter of habit for many physicians, is often simply the easier choice.

"It's easier to order a scan than to take the time to explain to patients that this isn't likely to be beneficial," he said. "Another thing is that many oncologists in the United States now own their own CT scanners; one could draw potential conclusions from that."

Thanks to high-profile editorials on the issue of CT scan overuse, such as one recently published in the New York Times, explaining the situation to patients might soon become easier.

A coauthor of that editorial, Rita Redberg, MD, MSc, director of Women's Cardiovascular Services at the University of California, San Francisco Medical Center, summed up the message about the judicious use of the scans in a video commentary for Medscape Medical News.

"The takeaways for us as a profession are really similar for primary care doctors, cardiologists, and radiologists, as well as emergency department physicians, in that we need to evaluate every test — and in particular imaging tests that use ionizing radiation — such that the benefits of this test will outweigh the risks, and we've considered alternatives, done a really careful history and physical examination, and think the tests will not just give us information," she said.

"Of course, all tests will give us information, but will they give us information that we couldn't have gotten from a nonionizing test or a history? And will they give us information that actually leads to a treatment that will lead to better outcomes and a treatment that we couldn't have arrived at without the use of an imaging test?"

The study authors, Dr. Kahl, Dr. Armitage, and Dr. Redberg have disclosed no relevant financial relationships.

19th Congress of the European Hematology Association (EHA): Abstract BSSUB-3488. Presented June 14, 2014.

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