BREAST CANCER SCREENING
Breast cancer is the most common cancer among women. Mammogram (MMG) is the only screening test shown to reduce breast cancer related mortality.
There is general agreement that screening should be offered at least biennially to women 50-74years of age. A meta-analysis of 13 randomized trials found 26 percent reduction in the relative risk of breast cancer-related mortality.
For women 40 to 49 years of age, the risks and benefits of mammography are closely balanced. The decision to perform screening should take into consideration the patient’s risk, values, and comfort level of the patient and physician.
The screening MMG should be started earlier if the women lifetime breast cancer risks estimate of more than 20% or who have a BRCA gene mutation. These women should undergo MMG at 25 years of age or 5-10 years younger than the earliest age of breast cancer diagnosed in the family.
There is no information from clinical trials about effectiveness of screening women older than 75 years. It is recommended that as long as an older woman is in good health and remains a candidate for breast cancer treatment if necessary, she should continue to be screened.
The American College of Obstetrics and Gynaecology (ACOG) recommends annual screening for younger women (aged 40-49 years) due to the comparatively rapid growth of breast cancers in this age group. Women older than 50 years should have screening every one to two years.
Women should be aware of any changes in their breasts. However, teaching breast self-examination does not improve mortality and is not recommended.
Ultimately, the goal of screening is not maximize the number of women who have mammography, but to help them make informed decisions about screening, even if that means the decision of not screening.
For a biennial screening at 40 years of age compared to 50 years will extend the life of fewer than one woman for every 1000 women screened. Comparatively, starting biennial screening at 50 years of age compared to 60 years will extend one to two women for every 1000 screened. Biennial screening between 60-69 years of age would extend the lives of three to four women for every 1000 screened. For all of these age groups, 350-500 women will have at least one false positive result over 10-year. Although the exact numbers of women who would be overdiagnosed and over treatment is not known, the best estimates are that it affects about six women per 1000 in their 40s, eight in their 50s. and 10 in their 60s. Although the benefits of screening increase with age, so do the harms; the balance between benefits and harms appear similar in all age groups. All eligible women should understand these number when considering screening mammography.