Specialists may downplay the harms of mammography in younger women - OregonLive.com

Dania Maxwell/The OregonianA Portland woman undergoes screening mammography at a Kaiser Permanente medical office in this August 2011 file photograph.

Expert recommendations on mammography couldn't be more confusing for women in their 40s. 

Some guidelines urge all women 40 or older to get a screening mammogram every year. Others recommend screening once every two years starting at age 50, and tell younger women to make an individualized decision after carefully weighing the pros and cons. 

A new study raises the possibility that groups advocating earlier and more frequent mammography may be motivated in part by the financial self-interest of specialists who perform screening and diagnostic imaging. The promotion of earlier screening by radiology and cancer specialists also may reflect their daily exposure to patients ill with cancer, the researchers write in the Journal of Clinical Epidemiology. 

Dr. Susan L. Norris, an associate professor at Oregon Health & Science University, and others researchers analyzed the authorship of 12 screening guidelines for women at average risk for breast cancer. (For women in their 40s with above average risk, the benefits of screening are more pronounced; more on that below) 

Dueling Guidelines

U.S. Preventive Services Task Force: "The USPSTF recommends biennial screening mammography for women aged 50 to 74 years. The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take patient context into account, including the patient's values regarding specific benefits and harms."

American College of Radiology: "Asymptomatic women 40 years of age or older should have an annual screening mammogram.”

Having radiologists among the authors seemed to guarantee that a guideline would recommend earlier and more frequent screening. Radiologists accounted for 59 of the 125 physician-authors of the eight guidelines calling for routine screening starting at age 40. There were no radiologists among the 53 physician-authors of the four guidelines that recommend individualized decisions for women younger than 50. More than 90 percent of the authors of those guidelines were primary care physicians. 

"We don't know why some specialties appear to recommend mammography more than other specialties. Different specialties have different perspectives when looking at the same body of evidence," Norris said. "There is evidence from other studies to suggest that physicians who deliver a particular service or who gain financially from using a particular surgical center, recommend that service more frequently than do physicians without those interests." 

Dr. Carol H. Lee, a radiologist in New York and representative of the American College of Radiology, said her organization advocates for annual mammography starting at 40 because studies repeatedly have shown it saves lives. 

"To say that it is based on a financial conflict of interest is completely ridiculous," Lee says. "On the scale of harm versus benefit, it's a subjective value judgement. People have different values," she says. "That's what it comes down to."

Mammography screening before age 50 is controversial because it exposes large numbers of healthy women to potential harms. Inevitably, some who are screened will undergo unnecessary cancer treatment because of over-diagnosis: the detection of harmless tumors that are dormant, destined to regress without treatment or growing so slowly the patient dies of other causes before the tumor causes illness. 

In younger women, the benefits may not justify the harms. Among women age 40 to 49 getting screened, the rate of breast cancer deaths is about 29 per 10,000, compared with 31 per 10,000 among those not getting screened, based on the combined results of eight clinical trials analyzed for the U.S. Preventive Services Task Force in 2009. 

For every 10,000 younger women screened for 10 years, 5 are likely to avoid death from breast cancer. But about 600 to 2,000 women will have a false positive result that requires them to undergo a biopsy, according to a 2009 analysis in the Annals of Internal Medicine. And 10 to 50 healthy women will be overdiagnosed and subjected to unnecessary cancer therapy: they will have either a part of their breast or the whole breast removed, and they will often receive radiotherapy and sometimes chemotherapy. 

Rather then declaring a one-size-fits-all recommendation for average-risk women in their forties, primary care groups such as the American College of Physicians say screening mammography decisions should be based on benefits and harms -- and each woman's preferences and breast cancer risk profile. 

Risk factors may tip the balance 

For women with certain risk factors, starting mammography screening at age 40 may be as beneficial as it is for average risk women after 50. A pair of studies in the Annals of Internal Medicine this week identified two factors that appear to tip the balance in favor of screening because they double the risk of breast cancer:

• A sibling or parent with breast cancer.
• Extremely dense breast tissue, as viewed by X-ray mammography.

Having second-degree relatives with cancer increased the risk by 1.5 to 2 times, as did a previous suspicious mammogram that led to a biopsy, and having partially dense breasts.

“We distilled the list down to really just a few factors that are of high enough magnitude to make a difference," said co-author Dr. Heidi Nelson, medical director of cancer prevention and screening for the Providence Cancer Center and research professor at OHSU. "Focusing on those select few might make it a more focused decision.” 

Current use of birth control pills, having never given birth, or reaching age 30 before giving birth increased risk by less than 1.5 times or not at all.  “They fall pretty far short of that threshold,” Nelson said.

Newer digital mammography is more sensitive than older film-based mammography. But digital equipment is likely to worsen the harm tradeoff in younger women, the studies found, because it produces more false-positives.

The findings are too preliminary to change expert guidelines. But they provide estimates of risk to help younger women weigh screening. A weakness of the new analysis was its assumption mammography works just as well in women with risk factors, which isn't always the case. Dense breast tissue, for instance, worsens the performance of mammography and some studies suggest that mammography isn't sensitive enough to increase detection even if done annually in women with extremely dense breast tissue.