Mammography Screening - Harms verses Benefits

Jessica Stray


Breast cancer is a leading cause of morbidity and mortality for women worldwide (Kearney & Murray, 2009). New Zealand is no exception as breast cancer affects around 2,750 (killing over 600) women annually (Breast Cancer Aotearoa Coalition, 2010). Severe social, emotional and economic costs are associated with the high prevalence of this disease. Programs have been implemented to reduce the affect breast cancer has on society. In New Zealand, this consists of the Breast Screening Aotearoa national program where women aged 45-69; receive free mammograms biannually (National Screening Unit, 2013). However, mammography-screening programs entail potential problems and practice issues such as anxiety and stress caused by false positive results and over diagnosis. The following literature review demonstrates the two predominant harms mammography screening has on women including, over diagnosis and false positive results. These harms are contrasted with the major benefits: decreased mortality and the effect on the rate of subsequent screening despite false positive results. Finally the recommendations of further research and more effective information and education are discussed.

While in the clinical setting of primary health I became aware of the controversy among the medical profession regarding the effectiveness of mammography screening, I discovered that women within the screening age group who are receiving mammograms are faced, due to over diagnosis, with the stress, anxiety and trauma of receiving false positive results and unnecessary treatment for tumors. The practice issue of physiological distress for women has caused me to question the effectiveness of mammography screening.

The search Question has been formulated using the PECOT model.

Question: What harm does mammography screening cause?

PECOT   category

Information   relating to question




This is   the age range recommended by the Ministry of Health for breast cancer   screening. It is this population who receive free mammograms under the Breast   Screening Aotearoa national program.




Women   who participate in mammography breast cancer screening.


I will   look at articles, which study the effectiveness of mammograms, and the effect   mammograms have on participants.

Comparison   / Control

Do the   potential negative side effects of having a mammogram outweigh the benefits?


To   explore if mammograms cause more harm to participants than benefits.


Mammograms   are still recommended despite potential harms and risks.


Mammograms   are recommended in New Zealand as well as worldwide through the World Health   Organization.


Not   applicable


Not   applicable

Search Question: In women aged 45-69 years as recommended in New Zealand does mammography screening result in more negative side effects than benefits to participants?


Harms of mammography screening

The issue of over diagnosis has been raised as one of the most significant negative side effects of mammography screening (Puliti, Miccinesi, Zappa, Manneschi, Crocetti, & Paci, 2012). It causes harm to participants by leading to unnecessary lumpectomies, mastectomies and other possible cancer treatments such as chemotherapy and radiation treatment as well as psychological distress (Kearney & Murray, 2009). Over diagnosis is defined by Duffy et al. (2010) as “the diagnosis of cancer as a result of screening that would not have been diagnosed in the women’s lifetime had screening not taken place” (p. 25). Multiple studies have been conducted regarding the incidence of over diagnosis in mammography screening. However large variations in estimates are present due to the method of statistical analysis used by researchers. According to Kalager, Adami, Bretthauer, and Tamimi (2012) in a nonrandomized setting, which is how most mammography over diagnosis research is currently conducted “there is no generally accepted analysis that would be universally applicable to allow this problem to be overcome” (p. 491). Therefore large variations in over diagnosis estimates, which currently range from 0% to 54%, will continue to prevail (Kalager et al., 2012). Not only do estimates vary depending on analysis, but also if ductal carcinoma in situ (DCIS) is inclusive or exclusive to estimates for invasive cancer (Kalager, Adami, & Bretthauer, 2014).

In a research study of women aged 50- 69 years invited to participate in a Norwegian screening program, it was estimated the rate of over diagnosis was 18% to 25% which suggests 6 to 10 women for every 2500 invited to the study were over diagnosed (Kalager et al., 2012). This is supported by results from a Canadian study, which presented a 22% rate of over diagnosis in women aged 40 to 59; thus 22% of screen detected invasive cancers would not have reduced the women’s life expectancy if left undetected. (Kalager et al., 2014). In both of these studies researchers focused only on women with invasive breast cancer, thus excluding those with DCIS which should result in a higher estimate of over diagnosis, as one in four breast cancers detected in screening programs are a result of DCIS (Puliti et al., 2012; Kalager et al., 2014). Keen (2010) illustrates how the inclusion of DCIS significantly increases the rate of over diagnosis. The over diagnosis estimate for invasive cancer was 35% which increased to 52% when DCIS was included. At age 50 almost half of screen-detected cancers represent over diagnosis of pseudo disease.  Because physicians generally initiate treatment for all true positives, women with pseudo disease can only be harmed my mammography screenings, as they have to endure the side effects, mortality risk and economic cost of treatment. He also suggests that women aged 40-50 participating in mammography screening are 10 times more likely to experience over diagnosis and over treatment than have their life saved by mammography (Keen, 2010). Over diagnosis and overtreatment of cancers causes implications for clinical practice as it produces doubt if mammography-screening programs should even exist. Over diagnosis causes us to question mammography’s ability to diagnose breast cancer successfully in its early stages. It also creates excess cost, not only to the health care system, but also to health care professionals, and the participant themselves (Kalager et al., 2012).

In addition to over diagnosis another negative side effect of mammography screening is false positive results as 50%-63% of women who undergo mammography screening can expect at least one false positive in their lifetime, which causes long-term psychological harm (DeFrank et al., 2012; Brodersen & Siersma, 2013).  The younger the women the greater risk for false positives because of denser breast tissue (Brodersen & Siersma, 2013; Mandelblatt et al., 2009). According to Brodersen and Siersma (2013) false positive results are not harmless, as illustrated by the results of their study. Women who experienced false positive results reported greater negative psychological consequences than those who received normal findings. In the first six months following a false positive result, women experience similar impacts on psychological wellbeing as those who were diagnosed with breast cancer.  They experienced a sense of dejection and anxiety as well as negative impacts on sleep, behavior, inner calmness and sexuality. Although these thoughts improved over the following 6 months, for a period of three years after being declared free of cancer, women with false positives reported greater negative psychological consequences compared to women with normal findings (Brodersen & Siersma, 2013). Similarity Brett and Austoker (2001) also found that 35 months after a false positive women still reported negative psychological consequences. Hafslund, Espehaug and Nortvedt (2012) had similar results, which showed an increase in anxiety (mean 4.6) and depression on recall, which remained increased until six months after screening. The implication on clinical practice as a result of these findings is that information about the existence of false positives results should be improved. By increasing participant knowledge on the risk of false positives initial psychological effects on women may be decreased (Hafslund et al., 2012).

Benefits of mammography screening

The benefit of mammography screening in terms of decreased mortality is far greater than the harm of over diagnosis according to a study by Duffy et al. (2010). For every 28 cases diagnosed, approximately 2-2.5 lives are saved and one case is over diagnosed. Thus the benefit of deaths being prevented is double the harm of over diagnosis. Due to mammography screening programs in the UK there has been a 28% mortality reduction (Duffy et al., 2010).  A study by Puliti et al. (2012) also estimates a significant mortality reduction due to mammography screening varying from 45% among 50-59 year-old women and up to 51% among women 60-69 years. This study also concludes that the benefits from mammography screening outweigh the harms estimating that that the overall cost to save one life corresponds to no more than one over diagnosed tumor  (Puliti et al., 2012). Mandelblatt et al.’s study (2009) demonstrated that screening biannually from ages 50- 69 resulted in a 15% to 23% reduction in breast cancer deaths when compared to populations with no screening. It has been clearly demonstrated that mammography achieves exactly what it is designed to do. In populations with established mammography screening programs breast cancer mortality has been reduced by 15% to 25% and even up to 51% in some studies, by detecting early stage invasive and non invasive tumors where treatment is less harmful as metastasis has not yet occurred (Schousboe, Kerlikowske, Loh & Cumming, 2011). As a result of mammography we have the ability to diagnose breast cancer in its early stages to increase survival rates, which illustrates that mammography is in fact an effective and beneficial tool for breast screening. However advances are yet to be made on how to treat early-diagnosed invasive and non-invasive cancer once it has been identified, which is where harm can be caused (Kaplan & Malmgren, 2013).

Although false positive results cause negative psychological effects, various studies have suggested that false positive results have no significant impact on subsequent screening. Studies have identified participant’s return for subsequent screening despite receiving previous false positive results. Andersen, Vejborg and Euler-Chelpin’s (2008) study on the participation behavior following a false positive test demonstrated women with a false positive result participated to the same extent as women with a negative test in subsequent mammography screening rounds. In fact in the USA women who received a false positive result were morelikely to return for subsequent mammography screening and thought more about the positives of mammography screening than those who received normal results. European countries generally found no significant effect of false positives on subsequent screening (DeFrank, 2012). Defrank et al. (2012) highlight the importance of physician support and advice following a false positive and that increased physician involvement resulted in higher subsequent screening participation. Anxiety, stress, discomfort and cost associated with false positives cannot be disregarded, as they are significant practice issues, which may have negative public health consequences. However, this means that support, education and more effective individualized information are required on the prevalence of false positive results. If women have insight and are well informed they would act appropriately on such information and thus protect themselves from potential harms (Hafslund et al., 2012)


Predominantly breast radiologists deny significant problems in over diagnosis and in 2010 the American Cancer Society did not mention over diagnosis as a limitation of mammography (Keen, 2010). Kaplan and Malmgren (2013) suggest that the issue we face is not whether screening with mammograms should continue based on the potential harm that it may over diagnose, but rather how to treat early diagnosed invasive and non- invasive cancer once it has been found by mammography screening. Early diagnosis allows for effective and less toxic treatment with reduced population mortality (Kaplan & Malmgren, 2013). However, information available in order to predict tumor progression and aggressiveness is still very limited, especially for carcinoma in situ (Puliti et al., 2012). It is recommended that further research is needed to improve understanding of tumor progression. By establishing a method to determine the progression of tumors and if they will threaten the person’s life, we will learn how to distinguish between cases with a good prognosis, which require less treatment from cases with a bad prognosis requiring more treatment. This will in turn reduce the burden of unnecessary treatment and thus the harm of over diagnosis (Kaplan & Malmgren, 2013; Puliti et al., 2012).  Health care professionals should not discourage mammography screening simply because advances on how to appropriately treat early diagnosed cancers has not yet occurred. Until these developments occur it is imperative that breast cancer is diagnosed as early as possible to allow for survival with the least toxic treatment (Kaplan & Malmgren, 2013).

Health professionals should educate women regarding the well-known risks of false positives and over diagnosis rather than reject mammography screening. Studies by Keen (2010) and Kearney and Murray (2009) show that women are not sufficiently aware of benefits and risks of screening to make informed decisions. Blennerhassett  (2013) supports this by stating that screening information is “not wholly honest about the benefits and harms” (p. 40).  Being aware of improving quality of information screening is very important for organized mammography screening programs throughout the world (Hafslund et al., 2012). If women are provided with balanced information which comprehensively informs them about the potential risks and benefits, then women should be able to make more informed decisions about mammography screening, decreasing the potential harm and psychological impact (Hafslund et al., 2012; Kalager et al., 2012). 


In conclusion, mammography inevitably entails unintended harmful effects such as over diagnosis and false positive results. However, the benefits of mammography screening outweigh the negative aspects and, through the recommendations of further research and increased patient education these harms can be significantly reduced. Efforts must be made to reduce anxiety and psychological harm though adequate support and information from health care professionals, and further research will allow for more appropriate treatment. After reviewing the literature on the harms and benefits of mammography screening I acknowledge that harm can be caused to participants. However I believe these can be minimized predominantly though education and information and do not outweigh the benefits of decreased mortality. Therefore I believe, in women aged 45-69 years as recommended in New Zealand, mammography screening does not result in more negative side effects than benefits to participants, and is an effective tool for breast cancer screening.


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