Ultrasound combined with mammography is better at detecting breast cancer, says a new study published in the Journal of the American Medical Association.
The study was conducted by American and Canadian researchers. They set out to investigate how effective mammography alone was in diagnosing breast cancer in women at a high risk for the disease versus mammography paired with ultrasound.
The researchers found that:
- A mammogram alone detected 78 per cent of tumours
- Ultrasound had an 80 per cent detection rate
- Together, the two techniques found 91 per cent of tumours
Per 1,000 women, mammogram alone found 7.6 cancers, while mammography plus ultrasound found 11.8 cancers.
Dr. Roberta Jong of Sunnybrook Health Sciences Centre in Toronto, which was one of the sites that recruited women for the study, said that the study was done to find evidence to support the use of both ultrasound and mammogram when looking for breast cancer.
"It actually supports the impression we had, but we never had data for it, that you can find cancers very well," Jong told CTV's Avis Favaro.
"Each finds cancers the other can't, so they are complementary."
Despite ultrasound's benefits for catching cancer, it did result in more false-positive results.
In the study, which encompassed 2,600 women, mammogram had a false-positive rate of 4.4 per cent, ultrasound's was 8.1 per cent and the combined mammography and ultrasound rate was 10.4 per cent.
Dr. Paula Gordon of B.C. Women's Hospital said that for some women, ultrasound should be used in addition to mammograms when looking for breast cancer.
Mammograms still 'gold standard'
Gordon said that mammograms are very accurate in women with fatty breast tissue, but less so in women with dense breast tissue. However, mammograms are still the "gold standard" in breast-cancer screening, she said.
"It is the only test that has been proven in randomized control trials to reduce mortality from breast cancer," Gordon said.
"We can make the assumption that because the cancers we find using ultrasound for screening are about the same size and stage as the ones we find on mammography screening that the reduction in mortality would be the same, but that's an assumption. That cannot be proven without doing a randomized control trial."
Gordon also said that in some provinces, ultrasound is not covered, so the debate will continue about who should get ultrasound and when.
Jong said that currently, due to a shortage of ultrasound technicians in Canada, a widespread program offering ultrasounds to all high-risk women would not be possible. But it should be considered.
"The cancers we're finding on this are small, they're early, they've not spread to the lymph nodes," Jong said.
"These are the ones you want to find because they will make a difference for these women."
Breast cancer is the most common form of cancer in women, according to the Canadian Cancer Society. It is estimated that in 2008, more than 22,000 women will be diagnosed with the disease and 5,300 will die from it.
However, earlier detection has led to a decline in death rates since the mid-1990s.
In an editorial accompanying the study, Dr. Christiane K. Kuhl of the University of Bonn, Germany, said that this research will be part of an ongoing look into tests that can accompany, or be alternatives to, mammograms.
"Individualized screening schemes tailored to the individual risk and to the personal preferences of a woman may be the way to consider how to screen for breast cancer," Kuhl wrote.
"Whether in the long run, ultrasound or breast MRI will be more appropriate for this purpose remains to be seen."
With a report from CTV's medical correspondent Avis Favaro and producer Elizabeth St. Philip.
Abstract:
Combined Screening With Ultrasound and Mammography vs Mammography Alone in Women at Elevated Risk of Breast Cancer
Wendie A. Berg, MD, PhD; Jeffrey D. Blume, PhD; Jean B. Cormack, PhD; Ellen B. Mendelson, MD; Daniel Lehrer, MD; Marcela B锟絟m-V锟絣ez, MD; Etta D. Pisano, MD; Roberta A. Jong, MD; W. Phil Evans, MD; Marilyn J. Morton, DO; Mary C. Mahoney, MD; Linda Hovanessian Larsen, MD; Richard G. Barr, MD, PhD; Dione M. Farria, MD, MPH; Helga S. Marques, MS; Karan Boparai, RT; for the ACRIN 6666 Investigators
Context: Screening ultrasound may depict small, node-negative breast cancers not seen on mammography.
Objective: To compare the diagnostic yield, defined as the proportion of women with positive screen test results and positive reference standard, and performance of screening with ultrasound plus mammography vs mammography alone in women at elevated risk of breast cancer.
Design, Setting, and Participants: From April 2004 to February 2006, 2809 women, with at least heterogeneously dense breast tissue in at least 1 quadrant, were recruited from 21 sites to undergo mammographic and physician-performed ultrasonographic examinations in randomized order by a radiologist masked to the other examination results. Reference standard was defined as a combination of pathology and 12-month follow-up and was available for 2637 (96.8%) of the 2725 eligible participants.
Main Outcome Measures: Diagnostic yield, sensitivity, specificity, and diagnostic accuracy (assessed by the area under the receiver operating characteristic curve) of combined mammography plus ultrasound vs mammography alone and the positive predictive value of biopsy recommendations for mammography plus ultrasound vs mammography alone.
Results: Forty participants (41 breasts) were diagnosed with cancer: 8 suspicious on both ultrasound and mammography, 12 on ultrasound alone, 12 on mammography alone, and 8 participants (9 breasts) on neither. The diagnostic yield for mammography was 7.6 per 1000 women screened (20 of 2637) and increased to 11.8 per 1000 (31 of 2637) for combined mammography plus ultrasound; the supplemental yield was 4.2 per 1000 women screened (95% confidence interval [CI], 1.1-7.2 per 1000; P = .003 that supplemental yield is 0). The diagnostic accuracy for mammography was 0.78 (95% CI, 0.67-0.87) and increased to 0.91 (95% CI, 0.84-0.96) for mammography plus ultrasound (P = .003 that difference is 0). Of 12 supplemental cancers detected by ultrasound alone, 11 (92%) were invasive with a median size of 10 mm (range, 5-40 mm; mean [SE], 12.6 [3.0] mm) and 8 of the 9 lesions (89%) reported had negative nodes. The positive predictive value of biopsy recommendation after full diagnostic workup was 19 of 84 for mammography (22.6%; 95% CI, 14.2%-33%), 21 of 235 for ultrasound (8.9%, 95% CI, 5.6%-13.3%), and 31 of 276 for combined mammography plus ultrasound (11.2%; 95% CI. 7.8%-15.6%).
Conclusions: Adding a single screening ultrasound to mammography will yield an additional 1.1 to 7.2 cancers per 1000 high-risk women, but it will also substantially increase the number of false positives.
