Many breast cancers resolve on their own. Autopsy studies show that about 30% of women in their 50s have occult breast cancers that apparently come and go. It makes one wonder if we are massively overdiagnosing cancers and overtreating them as well. The trick is to know which cancers are dangerous and in need of treatment. Studies on mammograms over time have documented this fact and the data supporting this is presented. We don't have the natural history we need to know which cancers will clear. DCIS (ductal carcinoma in situ) only kills about 1-2% of people...yet most are treated with surgery, chemotherapy, and radiation and 98% don't need treatment at all!
Breast cancer screening needs to be improved. Identifying cancers on the basis of anatomical findings is insufficient; we need additional testing that goes beyond mammograms, ultrasounds, MRIs, or PET scans. This is why we should consider adding breast thermography because it is a test of physiology. While the FDA has approved breast thermography as an adjunct to mammography, it has not yet approved it as a stand alone test.
Prostate cancer is another example of overdiagnosis and treatment. Again, only about 2% of men with prostate cancer die from it.