A new study has found that women between 42 and 49 who get mammography screening at least every two years were 44% less likely to be diagnosed with late-stage breast cancer. In fact, over 50% of breast cancers were asymptomatic and diagnosed by mammography alone

Regular mammogram screening has been shown to be a useful screening tool for women in their 40s because it diagnoses breast cancer at an earlier stage. Findings in a recent study published in the journal Cancer indicate indicate that regular mammography screening for women in their 40s leads to diagnosis of breast cancer at earlier stage, improving the prognosis and allowing more effective and less body altering treatments.

Women between the ages of 42 and 49 without a prior history of breast cancer who received mammograms at least every two years were 44% less likely to be diagnosed with a later stage of breast cancer compared with women who had not received regular mammograms. The majority of breast cancers were asymptomatic and diagnosed by mammography alone.

Breast cancer is the leading cause of death for women in their 40s and this age group accounts for 25% of all breast cancer deaths. Mammography is currently the most sensitive test of breast cancer, potentially diagnosing tumors when they are small, local, and at an early stage with a better prognosis.

Mammography is a proven effective screening tool for women over 50, contributing to the fall in mortality observed for women of all ages with breast cancer. However, there has been little evidence that mammography is an effective screening test for women in their 40s. One study that included long term follow up suggested that mammography screening reduces the ten year risk of death by just 17% for women in their 40s, but other studies have shown no benefit.

Buseman et al investigated 247 women who were diagnosed with breast cancer between the ages of 42 and 49 from 1994 - 2000. Data was collected on demography, family history, prior mammography history, cancer stage, and estrogen receptor status of tumor and treatment. Cancer stage was categorized as "early" for stage 0 and I, and "late" for stages II-IV. "Screened" was defined as at least one normal screening mammogram within 24 months prior to breast cancer diagnosis. "Unscreened" patients included women diagnosed from their first screening mammogram, no prior history of mammogram, and mammography more than 24 months prior to diagnosis of breast cancer.

Among women who were screened with mammography, 39% had late stage breast cancer compared to 52% of unscreened women. Analysis of risk, including adjustment for variables such as age, family history, year of diagnosis, indicated that screened patients were 44% less likely than unscreened patients to be diagnosed at a later stage. Screening, therefore, was protective, with an adjusted relative risk of 0.56.

Analysis of all patients showed that mammography alone was able to diagnose 55% of asymptomatic screened patients and 61% of unscreened patients.

"This study is important because it provides clear evidence of a more favorable stage distribution of breast cancers among women in their 40s who had been previously screened with mammography versus women who had not been previously screened," the authors conclude.

"Mammography screening seems to matter for women aged 40-49 because it leads to earlier diagnosis and, thereby, also to a better prognosis and to improved opportunities for more effective, less radical treatments," add the authors.

SOURCE:
Cancer, January 15, 2003