You may wish to download this booklet on screening for breast cancer.
"When we first published this leaflet in 2008, the Summary was:
"It may be reasonable to attend for breast cancer screening with mammography, but it may also be reasonable not to attend, as screening has both benefits and harms.
If 2000 women are screened regularly for 10 years, one will benefit from the screening, as she will avoid dying from breast cancer.
At the same time, 10 healthy women will, as a consequence, become cancer patients and will be treated unnecessarily. These women will have either a part of their breast or the whole breast removed, and they will often receive radiotherapy, and sometimes chemotherapy.
Furthermore, about 200 healthy women will experience a false alarm. The psychological strain until one knows whether or not it was cancer, and even afterwards, can be severe."
These numbers were derived from the randomised trials of mammography screening. However, since the trials were performed, treatment of breast cancer has improved considerably. More recent studies suggest that mammography screening may no longer be effective in reducing the risk of dying from breast cancer."
If you read the NYT article, be sure to read the comments.