Saving Women's Lives Strategies for Improving Breast Cancer Detection and Diagnosis (2005) / Chapter Skim
Currently Skimming:
2 Benefits and Limitations of Mammography
2 Benefits and Limitations of Mammography
Pages 37-62
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From page 37... ...
SCREENING VERSUS DIAGNOSIS Mammography has two main uses, screening and diagnosis, and there are important medical and economic differences between the two. Screening mammography is an x-ray-based procedure applied to a woman who has no signs or symptoms of breast disease and is used for the early detection of breast cancer.
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From page 38... ...
Estimates of the sensitivity of screening mammography from different studies range from 83 to 95 percent.72 Specificity refers to the proportion of true-negative results, or tests that correctly indicate that a woman does not have breast cancer among screened women without breast cancer. Mammography specificities generally fall in the range of 90 to 98 percent.72 In other words, the risk of a false-positive mammogram is about 1 in 10.
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From page 39... ...
= Total number of cancer-free cases Positive Predictive Value (PPV) refers to the probability that a patient with a positive test actually has the disease.
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From page 40... ...
. One way to increase the positive predictive value of a screening test is to target the screening test to those at high risk of developing the disease, based on considerations such as demographic factors, medical history, or occupation.
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From page 41... ...
. These and numerous other reviews concluded that many of Gotzsche and Olsen's criticisms were unsubstantiated, and the remaining deficiencies in the screening trials were judged not to invalidate the trials' findings that screening mammography reduces breast cancer mortality.73 Gotzsche and Olsen's critique was based on judgments of the quality of the screening studies, but those judgments were based on misreading of the data and the literature.36,37 As is often the case, the eruption of a medical controversy receives more media attention than its resolution, and these expert reviews received relatively little media attention.
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From page 42... ...
It supported Gotzsche and Olsen's criticism of mammography and concluded that "screening for breast cancer does not affect overall mortality, and that the absolute benefit for breast cancer mortality appears to be small." International Agency for Research on Cancer of the WHO March 2002 The group, consisting of 24 experts from 11 countries, concluded that trials have provided sufficient evidence for the efficacy of mammography screening of women between 50 and 69 years. The reduction in mortality from breast cancer among women who chose to participate in screening programs was estimated to be about 35 percent.
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From page 43... ...
the availability of screening reduces mortality from breast cancer by 20 to 30 percent (reviewed by Duffy and colleagues in 2003) ,19 and that in a population that actually participates in screening mammography, the reduction can be considerably greater, nearly 50 percent.18,97 This is not to say that every woman who undergoes screening mammography will ben
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From page 44... ...
Breast cancers and microcalcifications generally appear as whiter areas on mammograms because they tend to absorb more x-ray photons; they can be difficult to detect against the relatively light background of dense breast tissue because of the lack of contrast between them and a dense breast background. Breast density is usually measured as part of mammographic interpretation by classifying a mammogram according to the 4-point Breast Imaging Reporting and Data SystemTM (BI-RADS®)
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From page 45... ...
This increases the probability of obtaining an examination without noticeable patient motion, which can degrade image quality and limit the ability to find cancers. Obesity is commonly associated with fatty breasts and accounts for more than 40 percent of the variance in breast density.6 Native American populations typically have lower density breast tissue, and Asian populations have greater density breast tissue than African American and white populations overall.
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From page 46... ...
Given the known difficulty in reliably measuring pain, it is important to evaluate the methodologies used in these reports.1,85 For example, Kornguth and his colleagues found that only 2 percent of women reported pain using a 6-point pain scale, whereas 75 to 85 percent of the same women reported pain when using the two more complex measures of pain (McGill Pain Questionnaire and the Visual Analog Scale and Brief Pain Inventory) .55 Recent, appropriately designed studies report that only 15 percent17 or 28 percent87 of women experienced moderate or severe pain.
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From page 47... ...
In one survey, women who were questioned immediately following screening mammography reported that the part of the procedure they found most stressful was waiting for results.87 Yet another study reported that 67 percent of women were unwilling to pay even a small fee of $25 for immediate results.81 In general, anxiety associated with waiting for mammography results does not appear to be significant for most women (reviewed in 2001 by Meystre-Agustoni and colleagues) .67 False Alarms An abnormal finding on a mammogram is cause for concern.b However, resulting psychological distress is usually transient84 and is generally resolved if a subsequent test indicates that the interpretation was, in fact, a false positive.
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From page 48... ...
, such as those that occurred in the 1930s to 1950s due to atomic bomb radiation, multiple chest x-rays, and radiation treatment for breast disease, were associated with increased incidence of breast cancer in women below age 35 at exposure.29,59 However, radiation sensitivity among women drops precipitously after age 35,59 and although some caution may be warranted for regular mammographic screening of women below age 35,60 calculations indicate that radiation risk is extremely small compared with the benefits, even for women in their forties.28,29,48 Moreover, since the early days of mammography, image quality has improved markedly (Figure 2-1) and radiation exposure has been greatly reduced, so that the average amount of radiation absorbed during a mammogram is now very low.112 It is estimated that 100,000 women who were screened annually from ages 50 to 75 would lose about 13 years from cA "suspicious" mammogram is not necessarily a "positive" mammogram (i.e., one that shows evidence of breast cancer)
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From page 49... ...
(Other aspects of BRCA gene mutations are discussed in Chapter 4.) THE DCIS DILEMMA Far outstripping the current rise in all breast cancers, the diagnosis of ductal carcinoma in situ (DCIS)
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From page 50... ...
Cessation of screening mammography, or any other screening modality, would not solve the problem of overtreatment.26 Instead, the solution lies in tailoring treatment to the biological characteristics of individual cases. Diagnosis of DCIS DCIS occurs when malignant epithelial cells proliferate within the breast ducts but remain confined by the basement membrane (a thin non dMost, but not all, cases of DCIS are detected by screening mammography; some cases are palpable and can be detected following biopsy for breast asymmetry or masses.
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From page 51... ...
BENEFITS AND LIMITATIONS OF MAMMOGRAPHY 51 A Invasive 400 350 300 250 100,000 200 per 150 Rate 100 50 0 1973 1978 1983 1988 1993 1998 2001 Year of Diagnosis <40 40-49 50 B Ductal Carcinoma In Situ 50 45 40 35 30 100,000 per 25 20 Rate 15 10 5 0 1973 1978 1983 1988 1993 1998 2001 Year of Diagnosis <40 40-49 50 FIGURE 2-2 Female breast cancer incidence (invasive and DCIS) by age-adjusted rates from 1973 to 2001.96
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From page 52... ...
Only about 10 percent of mammographically detected DCIS will appear as a mass or asymmetry without calcifications; most DCIS is suspected on the basis of mammographic microcalcifications.22,71,109 This contrasts with invasive cancer, which usually appears as a mass or density on a mammogram. Mammograms frequently underestimate the extent of DCIS, particularly for larger lesions.41,42,43,71 Calcifications associated with DCIS vary in size, form and density, although they tend to be grouped in clusters, lines, or segmental arrangements that follow the morphology of the duct.
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From page 53... ...
Studies of local recurrence rates (following local excision without subsequent radiotherapy) indicate that poorly differentiated, comedo-type tumors tend to recur earlier despite excision and radiotherapy (for excellent review, see Kessar et al., 2002)
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From page 54... ...
A small series of untreated women with DCIS, who were diagnosed before mammographic screening became widespread, were found to have more than the expected number of invasive breast cancers when compared to the general population.2,22,25,75 Similarly, increased risk for both DCIS and invasive breast cancer also has been reported in larger, more recent studies of women treated for DCIS.22,35,36,68,104 Findings from randomized trials indicate that the addition of radiotherapy and tamoxifen to breast-conserving surgery (BCS) reduces the chance of future invasive disease recurrence compared with BCS alone.22,31,32,47 Finally, recent molecular genetic studies suggest that most invasive ductal breast cancers arise from DCIS (reviewed by Feig, 2000)
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From page 55... ...
less than or equal to 4 cm, meanwhile acknowledging the inherent difficulty of accurately measuring DCIS lesions.71 Younger women tend to have a greater risk of local recurrence after BCS plus RT, which results at least in part from the biological characteristics of disease in younger women.105 Although no randomized trials have yet been published, retrospective studies indicate that total mastectomy improves disease-free survival of DCIS as com pared with BCS plus RT, but there is no evidence to suggest the superiority of mastectomy over BCS plus RT in terms of overall and breast-cancer-specific sur vival.3,69,89 There have been some reports of low recurrence rates following BCS alone for small-volume lesions with clear margins, but the maximum size of DCIS for which RT could be safely omitted is unknown.69,71 Three recent randomized con trolled trials demonstrated that BCS plus RT significantly reduces the incidence of local recurrence of DCIS.30,31,38,47,69 Most nonrandomized trials reported find ings consistent with these randomized trials and showed that adjuvant RT after BCS significantly decreased the incidence of ipsilateral (same side) breast tumor recurrence.13,52,69,89,101 Randomized trials show that recurrence with lumpecto my alone is approximately 30 percent at 10 years and reduced by half with radio therapy.
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From page 56... ...
1999. Predictors of local recurrence after treatment of ductal carcinoma in situ: a meta-analysis.
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From page 57... ...
2002. Detection of ductal carcinoma in situ in women undergoing screening mammography.
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From page 58... ...
1995. Mammographically detected ductal carcinoma in situ: are we overdiagnosing breast cancer?
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From page 59... ...
2003. Re: Detection of ductal carcinoma in situ in women undergoing screening mammography.
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From page 60... ...
1995. Continued local recurrence of carcinoma 15-25 years after a diagnosis of low grade ductal carcinoma in situ of the breast treated only by biopsy.
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1995. Ten-year results comparing mastectomy to excision and radiation therapy for ductal carcinoma in situ of the breast.
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From page 62... ...
1999. Long term follow-up of women with ductal carcinoma in situ treated with breast-conserving surgery: the effect of age.
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