Women's annual breast exams could be improved by adding ultrasound and magnetic resonance imaging (MRI) scans to the usual mammogram, according to a US study released on Tuesday.
The research, published in the April 4 edition of the Journal of the American Medical Association, found that those two technologies helped spot small cancers that mammograms had missed.
The study followed 2,662 women at high risk for breast cancer, particularly because of dense breasts or a family history of the disease. They agreed to undergo three independent screenings in one year, arranged in random order.
The three tests found a total of 111 cancers, for about 2.6 percent of the total group. Mammography, which is a low-energy X-ray of the breast, turned up 59 cancers, or 53 percent of the total cancers found.
Ultrasound, a scan that uses sound waves to produce a picture of the body's internal workings and is often used for pregnant women, found 29 percent of cancers on its own, independent of other tests.
MRI scans which use a magnetic field combined with pulses of radio wave energy, found a total of eight percent of cancers that the other two methods had failed to detect.
Eleven cancers, or 10 percent, were not found by any of the three screening technologies, said the study.
"Annual ultrasound screening may detect small, node-negative breast cancers that are not seen on mammography," said the study.
"Magnetic resonance imaging may reveal additional breast cancers missed by both mammography and ultrasound screening," it said, adding however that MRI is not suitable for all patients and can carry higher costs and risks than other methods.
According to Kristin Byrne, chief of breast imaging at Lenox Hill Hospital in New York, the study shows that alternative testing methods can help spot cancers that mammograms miss.
"Nearly half of the cancers would not have been detected with mammography alone," said Byrne, who was not involved with the study.
"Breast cancer is difficult to detect on mammography in patients with dense breast tissue. Ultrasound and MRI detect a significant number of breast cancers which are not seen on mammography" in these patients, she added.
"Additional yearly screening with MRI and ultrasound is important in high risk patients with dense breasts for early detection."
A separate study released on Monday by researchers at Harvard University found that mammograms tended to overdiagnose a significant number of cancers -- between 15 and 25 percent.
That study followed nearly 40,000 women with breast cancer in Norway. It found no drop in the numbers of women with late-stage disease between those who had yearly mammograms and those who did not undergo annual tests.
Even more, between 1,169 and 1,948 women were "overdiagnosed" -- meaning they were told they had cancer when their tumors would have caused no harm had they not been found.
"Mammography might not be appropriate for use in breast cancer screening because it cannot distinguish between progressive and non-progressive cancer," said lead author Mette Kalager, a visiting scientist at Harvard and a researcher at the Telemark Hospital in Norway.
"Radiologists have been trained to find even the smallest of tumors in a bid to detect as many cancers as possible," added Kalager.
"However, the present study adds to the increasing body of evidence that this practice has caused a problem for women -- diagnosis of breast cancer that wouldn't cause symptoms or death."
Concerns about false positives in mammograms have existed for years, leading some researchers to believe less frequent exams may be the answer.
Currently, the US National Cancer Institute recommends that women age 40 or older should have a screening mammogram every one to two years.
Breast cancer is the second most common cancer among US women after non-melanoma skin cancer, with about 202,000 new diagnoses per year and some 40,000 deaths according to the US Centers for Disease Control.