Frustrating that you got downvoted.

https://www.uspreventiveservicestaskforce.org/uspstf/recomme...

> The decision to start screening mammography in women prior to age 50 years should be an individual one. Women who place a higher value on the potential benefit than the potential harms may choose to begin biennial screening between the ages of 40 and 49 years.

> . For women who are at average risk for breast cancer, most of the benefit of mammography results from biennial screening during ages 50 to 74 years. Of all of the age groups, women aged 60 to 69 years are most likely to avoid breast cancer death through mammography screening. While screening mammography in women aged 40 to 49 years may reduce the risk for breast cancer death, the number of deaths averted is smaller than that in older women and the number of false-positive results and unnecessary biopsies is larger. The balance of benefits and harms is likely to improve as women move from their early to late 40s.

> . In addition to false-positive results and unnecessary biopsies, all women undergoing regular screening mammography are at risk for the diagnosis and treatment of noninvasive and invasive breast cancer that would otherwise not have become a threat to their health, or even apparent, during their lifetime (known as "overdiagnosis"). Beginning mammography screening at a younger age and screening more frequently may increase the risk for overdiagnosis and subsequent overtreatment.

> . Women with a parent, sibling, or child with breast cancer are at higher risk for breast cancer and thus may benefit more than average-risk women from beginning screening in their 40s.

> Go to the Clinical Considerations section for information on implementation of the C recommendation.

Here's a page that details the false negative rates for this type of screening:

https://www.uspreventiveservicestaskforce.org/uspstf/documen...

> Data based on results from a single screening round for women regularly receiving digital mammography indicated that false-positive results were common in all age groups (Table 1). The rate was highest among women aged 40 to 49 years (121.2 per 1000 women [95% CI, 105.6 to 138.7]) and decreased across age groups (P < 0.001). Rates of false-negative mammography results tended to increase with age, ranging from 1.0 to 1.5 per 1000 women, but did not statistically significantly differ across age groups.

> For women with initially positive mammography results, rates of recommendations for additional imaging were highest among those aged 40 to 49 years (124.9 per 1000 women [CI, 109.3 to 142.3]) and decreased with increasing age (P < 0.001). Rates of recommendations for biopsy did not statistically significantly differ across age groups and ranged from 15.6 to 17.5 per 1000 women.

> Rates of invasive breast cancer were lowest among women aged 40 to 49 years (2.2 per 1000 women [CI, 1.8 to 2.6]) and increased across age groups (P < 0.001). Rates of ductal carcinoma in situ also were lowest among women aged 40 to 49 years (1.6 per 1000 women [CI, 1.3 to 1.9]) and increased with age (P = 0.055). Women aged 70 to 79 years had the highest rates of invasive cancer (7.2 per 1000 women [CI, 6.4 to 8.1]) and ductal carcinoma in situ (2.3 per 1000 women [CI, 1.7 to 3.0]). Consequently, the yield of screening was more favorable for older women. For every case of invasive breast cancer detected by mammography screening in women aged 40 to 49 years, 464 women had mammography, 58 were recommended for additional imaging, and 10 were recommended for biopsy. In contrast, for women aged 70 to 79 years, for every case of invasive breast cancer detected by screening, 139 women had mammography, 11 were recommended for additional imaging, and 3 were recommended for biopsy.