Obviously, I am not more knowledgeable about breast cancer than a government-led panel of experts. Yet I know enough to look askance at advice that only women 50 and older get mammograms every two years and those in their 40s skip the test altogether.

New cancer-screening guidelines, published in the Annals of Internal Medicine, fly in the face of conventional wisdom and long-standing consensus from cancer groups, radiologists and other experts that women get annual mammograms starting at age 40.