Effect of mammographic screening from age 40 years on breast cancer mortality at 10 years' follow-up: a randomised controlled trial by Sue M. Moss in the December 9, 2006 issue of the Lancet found that, “Although the reduction in breast-cancer mortality observed in this trial is not significant, it is consistent with results of other trials of mammography alone in this age-group. Future decisions on screening policy should be informed by further follow-up from this trial and should take account of possible costs and harms as well as benefits.”1 In real numbers, this study found that after an average of 10.7 years of screening there would possibly be one less death for every 2512 women undergoing annual mammography.

Comments from an accompanying editorial by Benjamin Djulbegovic brought up these important concerns about mammography.2

“False-negative screens might lead to inappropriate reassurance and delays in diagnosis, whereas false positives might result in unnecessary biopsies and additional imaging studies. However, the main harms associated with screening mammography relate to potential death from radiation-induced breast cancer. Although the overall reduction in death from breast cancer during the 10–15 years' follow-up in trials of screening mammography is clear, the anticipated peak for radiation-induced breast cancer occurs some 10–20 years after exposure, and risk might remain increased throughout a woman's life. A model estimated that starting screening mammography at age 40 years is justified if associated with decreased relative risk of death from breast cancer by 20% or more—assuming that this theoretical model is correct and accurate.” (This study showed a nonsignificant relative risk reduction of 17%—therefore, mammography is not justified.)

“Although the best estimates of harms from screening mammography seem to be less than the benefits, they remain too uncertain to conclude with a high level of confidence that screening mammography in this age-group is associated with a net benefit. Every woman, with her physician's guidance, should decide whether regret will be greater if she develops breast cancer that could have been detected earlier by screening mammography, or if she develops breast cancer later in life as a result of screening mammography itself.”

Comments: The burden of proof resides with those recommending the tests and treatments. This study clearly states the proof of benefits is lacking. The reason mammography fails women is because this measurement is crude and on average detects cancers only after they have been growing 8 to 14 years—by this time if the lump detected is truly cancer—often referred to as invasive cancer—then the disease has spread to the rest of the body and is unreachable by surgery or radiation.

Mammography harms a woman by finding “disease” that would have never threatened her life. In many cases mammography detects a condition called ductal carcinoma in situ (DCIS). This is not cancer, but when detected it is still treated aggressively with surgery and radiation. DCIS rarely turns into a life threatening cancer. Thus, for women for whom a cure is possible (those with DCIS) early detection and treatment are not necessary, while for women for whom cure is necessary (those with invasive cancer), this goal is rarely possible because the disease has already spread beyond the boundaries reached by local treatment (radiation and surgery).

After 10 disappointing trials, what I keep hearing from my colleagues and many women is, “Mammography remains the best opportunity doctors have to offer women.” But that’s not true; there is something better for preventing breast cancer, which is an enthusiastic recommendation to change their diet.

1) Moss SM, Cuckle H, Evans A, Johns L, Waller M, Bobrow L; Trial Management Group. Effect of mammographic screening from age 40 years on breast cancer mortality at 10 years' follow-up: a randomised controlled trial. Lancet. 2006 Dec 9;368(9552):2053-60.

2) Djulbegovic B, Lyman GH Screening mammography at 40-49 years: regret or no regret? Lancet. 2006 Dec 9;368(9552):2035-7.

Source: Dr. John McDougall, M.D. www.drmcdougall.com