Screening Mammography for Forty-Something Women: New Analysis Emphasizes Benefits of Yearly Exams


2000/10/10 -

Background Reference Information:

Current interpretations of trial experience and community screening programs suggest that annual mammography is likely to be more effective for the early detection of breast cancer in women between 40 and 49 years of age than screening that is conducted at longer intervals, according to Robert A. Smith, PhD. Although the value of screening mammography for women younger than 50 has been the subject of intense, and sometimes contentious, debate over the past two decades, Dr. Smith believes that the evidence for annual screening is now clear.

Writing in the September/October issue of CA—A Cancer Journal for Clinicians, Dr. Smith, who is Director of Screening for the American Cancer Society, Atlanta, GA, observed that tumors found in women younger than 50 tend to progress at a faster rate, often change more readily from a lower to a higher grade of malignancy, and spread to lymph nodes more quickly than those discovered in women 50 years of age or older.

Moreover, the preclinical detectable phase—which is when a small tumor has already developed and is detectable by mammography but is not yet palpable—is shorter in women between 40 and 49 compared with their older counterparts.

"Evaluation of survival according to tumor characteristics demonstrates that breast cancer is not an inherently different disease in women younger than 50 compared with older women," Dr. Smith explained. "Nevertheless, evidence about tumor progression rates indicates that shorter screening intervals are required in younger women to detect tumors at a favorable stage during the preclinical phase."

Based on his extensive review of the literature and a detailed evaluation of the complex factors involved, Dr. Smith and other experts suggest that for women younger than 50, annual (as opposed to biannual) screening mammography is likely to be more effective for identifying early tumors while they are still highly curable.

A Canadian research group recently reported that, for women in their fifties, self-breast examination plus annual clinical breast examination were roughly equivalent to annual screening mammography alone with respect to preventing breast cancer deaths. Although this controversial study focused on women 50 years of age and older, and Dr. Smith’s article discussed women in their forties, he reconfirmed that the "American Cancer Society remains committed to the efficacy of mammography in women 40 and older and stands by its guidelines." For women with average risk of breast cancer, the ACS guidelines recommend monthly self-breast examination starting at age 20, clinical breast examination every three years between the ages of 20 and 39,and yearly clinical breast exams and mammography starting at age 40.

Noting that the Canadian study had been criticized for problems with randomization, poor quality mammograms, and lack of properly trained radiologists, Dr. Smith also pointed out that this was the only study that found higher rates of lymph-node positive breast cancers in women who had had mammography than in those who had not. These results would not be entirely unexpected, he said, "if you consider that the benefit of a very high quality clinical breast exam was being compared with poor quality mammography in a study that was also plagued with unexplained, but clearly evident problems with study randomization. More to the point," he added, "the findings are discordant with the larger body of scientific research on the effect of mammography on early breast cancer detection."

The "principal advantage of mammography is to find breast cancer when it is very small and before the cancer has spread to the lymph nodes," Dr. Smith said. "Women over the age of 40should use monthly self-exam and yearly clinical exam in addition to mammography, not as substitutes for it," he concluded.

Joann Schellenbach
National Director Media Relations
American Cancer Society