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Diagnostic accuracy may be improved via 3D scanning technique
By admin at 2012-11-21 20:08
Diagnostic accuracy may be improved via 3D scanning technique

According to the results of a new multi-center study published in the journal Radiology, the use of three-dimensional breast imaging, known as tomosynthesis, could improve diagnostic accuracy.

"This is the first major advance in breast imaging and breast cancer screening since the development of breast MRI," said lead researcher Elizabeth A. Rafferty, M.D., director of Breast Imaging at the Avon Comprehensive Breast Center at Massachusetts General Hospital in Boston. "The beauty of tomosynthesis is that it addresses two major concerns with screening mammography: missed cancers and false positive rates."

According to the National Cancer Institute, there is convincing evidence that screening mammography reduces breast cancer mortality in women between the ages of 40 and 74. However, as many as 30 percent of breast cancers are not detected by mammography and an additional eight to 10 percent of women who undergo a screening mammogram are recalled for further testing when no cancer is present (called a false positive result).

Unlike a screening digital mammogram, which involves two X-ray images of each breast, breast tomosynthesis captures multiple, low-dose images from different angles around the breast. The images are then used to produce a three-dimensional reconstruction of the breast. Both digital mammography and breast tomosynthesis, which was approved by the United States Food and Drug Administration (FDA) in February of 2011, can be performed on the same mammography equipment in rapid succession.

Dr. Rafferty's study involved 1,192 women recruited from five sites, of whom 997, including 780 screening cases and 217 women who needed pre-biopsy breast imaging, had complete data sets. Each of the women underwent a standard digital mammogram followed by breast tomosynthesis. The total radiation dose for the combined procedure was less than 3 milligray, which is the FDA limit for a single mammogram.

Drawing from the eligible cases, the researchers then conducted two reader studies involving 312 and 310 cases, respectively. Twelve radiologists participated in the first reader study; 15 radiologists in the second. A total of 48 cancers were included in the first reader study; 51 cancers in the second.

Compared to digital mammography alone, the use of both standard mammogram and tomosynthesis resulted in increased diagnostic accuracy for all 27 radiologists. Additionally, the diagnostic sensitivity of the combined exam — or the rate at which cancer present in the breast was correctly identified — increased by 10.7 percent for radiologists in Reader Study 1 and 16 percent for radiologists in Reader Study 2.

"Almost all of the gains in diagnostic sensitivity with the combined modality were attributable to the improved detection and characterization of invasive cancers, which are the cancers we are most concerned about because of their potential to metastasize," Dr. Rafferty said.

With the addition of breast tomosynthesis to standard digital mammography, false positive recall rates also significantly decreased for all 27 of the radiologists. Absolute recall rate reductions of 38.6 percent and 17.1 percent were seen in Reader Studies 1 and 2, respectively.

"In the clinical setting, we would expect that type of reduction in recall rate to translate into a substantial number of unnecessary diagnostic tests being avoided," Dr. Rafferty said.

12 comments | 2717 reads

by gdpawel on Thu, 2012-11-22 01:44
This is interesting! It seems to follow the observations of at least two other diagnostic techniques in cancer medicine.

Currently, there is no adequate diagnostic test for ovarian cancer. However, by using the combination of HE4 and CA125 tumor markers, physicians can better triage patients for care and refer them to the appropriate specialist whether at a community hospital or large academic institution.

It was only last year that results of a pilot study were published in the journal of Gynecologic Oncology that showed the combination of HE4 and CA125 provided the highest level of sensitivity and specificity out of all marker combinations for predicting the presence of ovarian cancer.

The combination performed well in both pre- and post-menopausal women, accurately stratifying 95% of patients with epithelial cancer as high risk and 75% of benign cases as low risk.

While some cell-death assay labs use singular endpoints (point of termination), functional cytometric profiling labs assess the activity of a drug upon combined effect of all cellular processes, using several metabolic (cell metabolism) and morphologic (structure) endpoints, at the cell "population" level rather than at the "single cell" level, measuring the interaction of the entire genome.

Just as using a combination of CA125 and HE4 makes identification more accurate, a combination of metabolic and morphologic endpoints makes functional cytometric profiling more accurate.

I like the idea that combining breast tomosynthesis to standard digital mammography, false positive recall rates are significantly decreased.

by gdpawel on Thu, 2012-11-22 06:03
(USA Today) - According to an analysis in the recent New England Journal of Medicine that's likely to reignite the running debate over the value of cancer screening, up to 70,000 American women a year are treated unnecessarily for breast cancer because they were screened with mammograms.

The study found that nearly one in three breast cancer patients (1.3 million women over the past three decades) have been treated for tumors that, although detectable with mammograms, would never have actually threatened their lives. The study lays bare the greatest risk of cancer screening, called "overdiagnosis."

The study's co-author H. Gilbert Welch of the Dartmouth Institute for Health Policy and Clinical Practice in Lebanon, N.H. says that overdiagnosis occurs when technology detects cancers that, although technically malignant, behave as if they're benign. Doctors have long known that some tumors aren't actually fatal. Instead, some remain dormant for years or even disappear on their own.

Doctors and public health campaigns typically emphasize the benefits of mammograms – such as the potential to detect cancers when they're smaller and more curable – but ignore the "huge human costs" of women who go through surgery, radiation and hormonal therapies for nothing, Welch says.

"We've suggested to women that having a mammogram is one of the most important things you can do for your health, and that's simply not true," Welch says. "I can't tell you the right thing to do, except to tell women the truth, tell them both sides of the story. We shouldn't be scaring women. This is a really close call."

Though policy experts are familiar with such tradeoffs, few others understand that, in any screening program, some women will be harmed while others are helped, says Fran Visco, president of the National Breast Cancer Coalition. Breast cancer therapies can be very toxic, leading to second cancers, heart failure and even death, Visco says.

"When you intervene in a healthy population, you better be sure you're helping them, because you can be sure you're harming them," says Visco, a breast cancer survivor, who wasn't involved in the new study. "If it were really clear mammograms saved a lot of lives, there wouldn't be this constant debate."

Authors acknowledge their paper doesn't offer any guidance to women diagnosed with cancer. Because doctors can't tell for sure which tumors are most dangerous, they treat all breast cancers — and even pre-cancers — as if they have the potential to kill, says co-author Archie Bleyer of St. Charles Health System in Bend, Ore.

In a statement, the American Cancer Society says "overdiagnosis is a matter deserving of attention," but it notes that other analyses have arrived at different estimates of the number of patients treated unnecessarily.

Len Lichtenfeld, the society's deputy chief medical officer, urged people to view the findings "with caution." Overall, "the benefits of screening mammography outweigh the risks and harms, which are an unavoidable part of breast cancer screening," Lichtenfeld says.

Rigorously designed clinical trials – the gold standard of medical evidence – have found that mammograms reduce the death rate from breast cancer by about 15% in women in their 40s and 50s and 30% for women in their 60s. More recent studies, though less rigorously designed, suggest the benefits could be even greater, says radiologist Barbara Monsees, speaking for the American College of Radiology.

"We know that overdiagnosis exists," Monsees says. Although doctors need better tools to differentiate lethal tumors from relatively harmless ones, Monsees says, "we should continue to screen, because we know we can save lives."

Eric Winer, head of breast medical oncology at Boston's Dana-Farber Cancer Institute, notes that the study found an 8% reduction in the number of women whose tumors were detected at more advanced stages. Even under a scenario in which mammograms led more than 1 million women to receive unnecessary treatment, the screenings would have prevented 410,000 diagnoses of late-stage cancer.

"We probably have to some degree oversold the benefits of mammography, but we still know that mammography is beneficial, certainly for women over the age of 50 and likely for some women under 50," Winer says. "I don't think we need to abandon mammography. It's still our best test, although we desperately need better tests."

Experts offer different recommendations about the frequency and timing of mammograms. The American College of Radiology and American Cancer Society both recommend women get annual mammograms beginning at age 40. The U.S. Preventive Services Task Force recommends that women be screened every other year beginning at age 50, but they should make up their own minds about whether or not to have mammograms before that.

Given the test's limitations, Winer says, women may choose to have fewer screenings to reduce their risk. "It certainly suggests that a woman who chooses to wait until she's 50 to have mammograms, or who chooses to have mammograms every other year, is making a rational decision," Winer says.

Barry Kramer, director of the National Cancer Institute's division of cancer prevention, says women should be presented with the full picture of mammography's risks and benefits.

Though women have been instructed that "early detection saves lives," relatively few are told that screenings also have costs, including the risk of undergoing surgery, radiation and drug therapy that doesn't help them, Kramer says. "The risks of overdiagnosis are real, and women ought to know about it," Kramer says.

One comment I've read about Welch's study is the one important additional point on mammography: 600,000 women have been enrolled in randomized trials of screening mammography and no overall mortality benefit is apparent after more than a decade of follow-up. Overall mortality is the only scientifically trustworthy outcome in such data. In other words, randomized clinical trials have shown that mammography doesn't save lives, and Dr. Gil Welch knows this. The science on mammography is that it doesn't work.


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