RSNA 2012 featured a number of lectures that spotlighted new research findings as well as consumer studies regarding women’s imaging. Here are the highlights.
By Elaine Sanchez Wilson
Breast density communication was just one of the hot-button topics discussed at this year’s Radiological Society of North America meeting, which through a variety of presentations highlighted new and exciting research on women’s imaging.
One preliminary study found that patients would be interested in supplemental screening exams if identified as having dense breast tissue, even with the possibility of false positives, out-of-pocket costs, and invasive procedures.
Jafi Lipson, MD, assistant professor of radiology at Stanford University School of Medicine, Stanford, Calif, and Haatal B. Dave, MD, MS, resident physician at Yale University School of Medicine in New Haven, Conn, sought to evaluate patients’ levels of awareness about their own breast density.
The survey is a timely one, given the pending federal legislation that would require radiologists to notify women about this medical information. Five states, including California, Connecticut, New York, Texas, and Virginia, have already passed similar bills, and more than 10 other states have bills in the works. New York and Connecticut are the only two states to require health insurance companies to cover the cost of supplemental screening exams for women with dense breast tissue.
“We knew that eventually due to this legislation, we would need to be communicating with patients, so we wanted to have a baseline understanding of what they knew,” said Lipson.
Women undergoing routine screening mammography at an outpatient radiology clinic affiliated with Stanford University Medical Center were asked if they knew their breast density and were educated on the association between higher breast density and increased risk of breast cancer. Among the 105 survey participants, 76% were unaware of their breast density and 40% had dense or extremely dense breast tissue.
“We wanted to see whether there were any associations between patient age or actual breast density and their awareness of breast density, and there were no correlations,” Lipson said. “There were many women with dense breasts who weren’t aware and many women with fatty breasts who were aware, but there wasn’t a predictable association at all; there was a distribution among all the densities.”
The study is the first in what the investigators hope will be a number of collaborations with hospitals serving various populations. Lipson admitted this initial study was basic, without any data collection on demographic information. Furthermore, the sample, which included 105 women, was relatively affluent and relatively white. “That’s why we’re trying to make plans to execute the study in a number of different settings—to see if the findings hold up,” she continued. Currently, the researchers have a partnership with the Santa Clara Valley Medical Center, which serves a community of Hispanic and Vietnamese patients, as well as low-income patients. Lipson said she also hopes to execute the survey in a predominantly African American population.
Due to the new reality regarding patient awareness, as well as the fact that breast density is a strong, independent risk factor for breast cancer, Lipson said she knew that radiologists would need to start exploring the option of supplemental screening, such as automated whole-breast ultrasound and contrast-enhanced mammography, at least on a research basis. She added that the survey not only offers a sense of the baseline awareness of the population, but it also provides researchers with a potential recruitment tool for patients.
Dave pointed out that although educating patients about the association between breast density and breast cancer risk is important, the topic has sparked debate in the medical and political spheres. Lipson explained that once patients are given this information, doctors may or may not be able to help them act on that information in a beneficial way. Moreover, there is a lack of maturity of the evidence to support the use of supplemental screening tools, Lipson added.
“I don’t want to come down on one side or the other regarding legislating this communication of information to patients, but I’m really excited that the RSNA media community has chosen to highlight our study because I think finding out what patients know is really important,” Lipson concluded. “I think it’s the first step toward understanding the patients that we’re trying to help.”
Women should begin receiving their annual screening mammogram at age 40, despite the revised guidelines issued by the US Preventive Services Task Force (USPSTF), according to researchers.
In the past, the USPSTF and the American Cancer Society (ACS) had recommended routine screening mammography for all women over the age of 40. However, in a controversial move in 2009, the USPSTF shifted their stance and recommended routine screening with mammography every 2 years for women 50 to 74 years old.
Still, the ACS and the American College of Radiology (ACR) hold that patients should receive them at age 40.
“Our study results have influenced our practice because when patients ask how often to get a mammogram—understandably confused by mixed messages they are getting—we can tell them that not only the literature, but also our internal review of our own practice, support the ACR and ACS recommendations of annual screening starting at age 40 over USPSTF 2009 recommendations,” said Elizabeth Arleo, MD, assistant professor of radiology at New York—Presbyterian Hospital—Weill Cornell Medical College in New York City.
Arleo and a team of researchers analyzed data on screening mammography at the hospital between 2007 and 2010. Over the 4 years, 43,351 screening exams were performed, which led to the detection of 205 breast cancers. Patients in their forties accounted for 19% of screen-detected breast cancers, over half of which were invasive.
“It seems unacceptable to potentially miss nearly 20% of the breast cancers we are identifying. This, in our view, would represent a substantial degree of underdiagnosis,” Arleo said.
Explaining its move to increase its age guidelines from 40 to 50, the task force said false-positive results are more common for women ages 40 to 49.
False-positive results are more common in younger women because the incidence of breast cancer increases with age, Arleo said. Furthermore, younger women may lack prior mammograms to establish stability. “However, the [task force rationale] suggests that something changes at the age of 50, which is inaccurate,” she continued. “The false-positive rate for women in their 50s is also higher than for women in their 60s since the prior probability of breast cancer goes up with increasing age. Singling out women in their 40s is arbitrary without basis in science or biology.”
Impact of Increased CT Utilization
Increased CT utilization and nuclear medicine examinations may increase the risk of breast cancer for specific women, including younger patients and individuals receiving repeat exams, according to a retrospective study presented at the meeting.
Investigators, who were led by Ginger Merry, breast imaging fellow at Prentice Women’s Hospital—Northwestern Memorial Hospital in Chicago, analyzed records of approximately 250,000 women enrolled in an integrated health care delivery system. Among patients, CT utilization increased from 99.8 CT scans per 1,000 women in 2000 to 192.4 CT scans per 1,000 women in 2010, representing an annual increase of 6.8%. In 2010, 46% of those CT examinations exposed the breast to radiation. Additionally, nuclear medicine imaging decreased from 39.3 scans per 1,000 women in 2000 to 27.5 scans per 1,000 women in 2010, signifying a 3.5% annual decline. Still, in 2010, 84% of nuclear medicine studies exposed the breast to radiation.
“The use of medical imaging that exposes patients to radiation has been increasing rapidly over the last decade and it is important to understand the risks that are associated with this radiation exposure,” Merry said.
“Until now, the impact of this increased use of imaging on radiation exposure to breast tissue and the subsequent risk of breast cancer has not been known,” said senior coauthor Rebecca Smith-Bindman, MD, professor of radiology and biomedical imaging at the University of California, San Francisco. “Our goal was to quantify imaging utilization and radiation exposure to the breast among women enrolled in an integrated health care delivery system and to use these data to determine the imaging-related risk of breast cancer from those studies.”
Reviewing CT dose information from 1,656 patients who underwent CT examinations that exposed the breast to radiation and estimating the patients’ effective radiation dose using a new automated computational method, the team found that the estimated breast radiation doses from CT were highly variable across patients, with the highest doses coming from multiple-phase cardiac and chest CT examinations, where successive images of the organ being studied are captured. Also, researchers analyzed the radiopharmaceutical volume and associated radiation exposure used in 5,507 nuclear medicine exams that exposed the breast to radiation.
“Young women receiving several chest and/or cardiac CTs had the greatest increased risk of developing breast cancer at approximately 20%,” said Diana Miglioretti, PhD, study coauthor and senior investigator at the Group Health Research Institute. “A 15-year-old girl with no risk factors for breast cancer would double her 10-year risk of developing breast cancer at 25.”
When asked about challenges and limitations that researchers faced, Merry explained that the large amount of data made the statistical analysis time intensive. Furthermore, according to Smith-Bindman, the study’s sample size was not large enough to assess patterns in the dose delivered over time.
The authors hope that the study’s findings will encourage ordering physicians and patients to consider thoroughly all the options before proceeding with CT imaging, especially in young women.
“The risks and benefits should always be considered before proceeding with any procedure that has a potential risk,” Merry said. “When alternative imaging, such as MRI and ultrasound, is available and can provide an answer to the clinical question, they should be considered. However, it is important to recognize that often CT is the only imaging modality that may be able to answer a clinical question and that the benefit of answering the clinical question may far outweigh the very small risk of cancer from the imaging.”
The researchers recommend that both the ordering physician and the radiologist should inform young women of the small risk of breast cancer associated with repeated, high dose CT scans that include the chest in the field of view.
Risks of Scatter Radiation
Thyroid cancer diagnoses in women nearly doubled from 2000 to 2008, and many concerned patients request that they wear thyroid shields during mammograms. However, new research has shown that radiation dose to areas of the body near the breast during mammography exams is negligible or very low and does not result in an increased risk of cancer.
Alison L. Chetlen, DO, assistant professor of radiology at Penn State Hershey Medical Center, and her fellow investigators set out to understand the potential impact of scatter radiation in 207 women, ages 36 to 90, from central Pennsylvania. In their study, which took place from October 2011 to April 2012, patients wore six optically stimulated luminescent dosimeters while undergoing two-view screening mammography. After the patients’ screening mammograms, a medical physicist analyzed the devices and researchers measured the dose received by the thyroid gland, salivary gland, sternum, uterus, and the lens of the eye.
All areas except for the sternum received less than 2% of annual background radiation dose.
Chetlen stresses that the dosimetry data should not be used as an exact measure of the scatter dose received by each organ, but rather as a guideline to be considered by physicians.
“The best way to educate the public is to put it into perspective and describe radiation in some way for [patients] to understand,” she continued. “One of the big teaching points of the study—one of the learning points for the public—is to understand that [various areas outside the breast] receive less than 2% of the average annual background radiation. The scatter radiation dose to these organs is very, very small.”
Elaine Sanchez-Wilson is a contributing writer for Axis Imaging News.