We have to let patientsknow that theimpact of mammography isnot that large-especiallyin women aged 40 to 49years. We simply do notknow whether early detectionof breast cancer leadsto improved outcomes inthis age group.
We have to let patientsknow that theimpact of mammography isnot that large--especiallyin women aged 40 to 49years. We simply do notknow whether early detectionof breast cancer leadsto improved outcomes inthis age group.At the individuallevel, only a modest benefit.It is still fair to say thatearly detection appears tosave some lives. In addition,early detection canshift the diagnosis of cancerto a stage where treatmentis often much lessdrastic, more easily tolerated,and much less expensive.However, physicianstend to overstate the benefitsof screening. For example,the benefit conferredby mammography--ifthere is one--is far fromdramatic. The most favorableestimate in the 8 randomizedtrials that haveexamined the impact ofscreening mammographyis that screening results inabout a 28% risk reductionin breast cancer mortalityin the 50-to-74-year agegroup.1What does that meanto the individual woman?The likelihood of deathfrom breast cancer is currentlyestimated at about3% over the course of a lifetime.2 Assuming a womanhas a mammogram everyyear or two, and assumingall the evidence is correct,the best-case scenario isthat the risk can be loweredfrom about 3% to a littleover 2%. When we look at itthis way, that 28% risk reductionis not as dramatic.Clearly, from a populationstandpoint, the potentialmortality reduction is verysignificant: the number ofwomen dying of breast cancercould be reduced bythousands. But the risk reductionat the individuallevel is modest. The benefitof screening women intheir 40s is even more marginal,because of the lowerincidence of breast cancer,poorer sensitivity of mammography,and generallygreater aggressiveness ofbreast cancers detected inthese younger women. Ithas been estimated thatone would need to screen1792 women aged 40 to 49every 1 to 2 years over a periodof 14 years to save 1life from breast cancer.3Downside of regularmammograms. Mammographyalso has its downside.Regular screening can createa great deal of worry--much of it needless. If awoman begins getting regularmammograms at age 40,there is virtually a 100%chance that some kind ofabnormality will show upthat will warrant at least afollow-up mammogram, anultrasound scan, or a callfrom the physician recommendinga 6-month followupexamination. It is alsolikely that over the courseof a lifetime she will undergoan unnecessary breastbiopsy (Figure 1).4Another risk ofscreening is finding malignanciesthat are not significant.Mammography is particularlygood at findingductal carcinoma in situ,which accounts for nearly20% of the 230,000 cases ofbreast cancer each year.However, we do not knowhow dangerous these malignanciesare. Many ofthem might never spread.Yet many women are havinglumpectomies for theseearly cancers.Even if a significantcancer is detected and treatedearly, we do not know inmany cases whether themalignancy is destined tobe aggressive or indolent.Early diagnosis may simplymean that we have extendedthe amount of time thepatient is alive knowing thatshe has cancer--not necessarilythat we have prolongedher life. She mightlive just as long with laterdiagnosis and treatment.Involving patients inthe decision to screen. Becauseof the uncertaintyand because of the medicolegalimplications, I dooffer mammography to allwomen 40 years and older.But I do not recommend ituniversally anymore. I tell a40-year-old woman that theevidence that we can saveher life with mammographyis not compelling.I am approaching olderwomen (ie, over age 70 to 75years) much the same way Ido women younger than50, but for different reasons.Older women are at higherrisk for developing breastcancer, and mammographyappears to perform better atdetecting early cancers inthem because breast densitydecreases with age. However,there is little evidencethat screening mammographyin older women saveslives. Moreover, the increasein competing mortality risksfrom other diseases that occurswith aging lessens thebeneficial impact of screening.Finally, older patientsmay have shifting values andpreferences that need to beexplored before screening isautomatically continued.The less evidence wehave of benefit, the greaterour obligation to share theburden of uncertainty withpatients and to involve themin the decision. In my initialtalk with a patient, we discussthe issues and the patientstates her point of view.If she wants to have annualmammographic screening, Ido not discuss the issueevery year. If she does notwant to be screened, I willask her the following year ifanything has changed.We must also try toprovide as much informationas possible in advanceof our visits with patients.For example, we can haveliterature in the waitingroom that outlines the prosand cons of the variousscreening tests. The moreinformed patients are beforethey see us, the lesstime we need to spend educatingthem in the officeand the more efficiently wecan discuss the issues.
Kerlikowske K, Grady D, RubinSM, et al. Efficacy of screening mammography:a meta-analysis.
National Cancer Foundation. SEERCancer Statistics Review, 1973-1999[Breast Cancer, Table IV-9]. Availableat: http://seer.cancer.gov/csr/1973-1999/. Accessed July 16, 2003.
Humphrey LL, Helfand M, ChanBKS, Woolf S. Breast cancer screening:a summary of the evidence forthe US Preventive Services TaskForce.
Ann Intern Med
Elmore JG, Barton MB, MoceriVM, et al. Ten-year risk of false positivescreening mammograms and clinicalbreast examinations.
N Engl JMed