Gerald Hurowitz, M.D.·Published 26 April 2011·10 min read
Key points
Breast cancer detection currently entails three distinct stages.
In the third stage, abnormalities labeled as malignant must be further characterized biochemically and staged according to tumor size and extent of invasion and metastasis to determine a prognosis and an appropriate course of treatment.
Monthly breast self-examination (BSE) is a common method of identifying lumps and other abnormalities in the breast.
Although the goal of finding smaller tumors at an earlier stage may be attained by BSE (Coleman, 1991), to date the evidence is not definitive that BSE improves the survival rate for women with breast cancer.
Breast cancer detection currently entails three distinct stages. The first stage is identification of an abnormality in the breast tissue either by physical examination or by an imaging technique (most commonly, mammography). Once identified, the abnormality must be diagnosed as benign or malignant by using additional imaging modalities or by biopsy and microscopic examination of the tissue morphology (Figure 1-4).
In the third stage, abnormalities labeled as malignant must be further characterized biochemically and staged according to tumor size and extent of invasion and metastasis to determine a prognosis and an appropriate course of treatment.
Monthly breast self-examination (BSE) is a common method of identifying lumps and other abnormalities in the breast. BSE in conjunction with screening mammography is currently advocated by many organizations, but it is also recommended for younger women who are not yet being screened by mammography. BSE was first advocated in the 1940s and 1950s, before the advent of screening mammography. Breast surgeons saw many patients whose tumors were too large for surgical removal, and they believed that regular self-examination of the breasts would result in earlier detection when surgery was still an option.
Although the goal of finding smaller tumors at an earlier stage may be attained by BSE (Coleman, 1991), to date the evidence is not definitive that BSE improves the survival rate for women with breast cancer. Furthermore, BSE can lead to an increase in unnecessary biopsies, especially in younger women (Semiglazov et al., 1992, 1999; Thomas et al., 1997).
Two large, randomized trials are ongoing in Russia and China and may help to answer some of these questions more definitively.
FIGURE 1-4Breast cancer management algorithm. SOURCE: Risk Management Foundation, Boston Massachusetts (May 23, 2000).
FIGURE 1-4 (Continued)Breast cancer management algorithm. SOURCE: Risk Management Foundation, Boston Massachusetts (May 23, 2000).
Breast physical examination by physicians is also widely practiced and advocated for women of all ages. Although clinical breast examination (CBE) has been studied in conjunction with mammography and one study has shown it to be beneficial in that context (the Health Insurance Plan of New York [HIP] trial), its use as a stand-alone screening tool has not yet been fully assessed. A large trial is being undertaken in India to determine the impact of screening by physical examination alone on breast cancer mortality (Jatoi, 1999). In Canada, a large randomized clinical trial has directly compared CBE alone with screening mammography plus CBE. The results showed no significant difference in breast cancer mortality rates between the two study arms at 7 and 13 years after the initiation of screening (Miller et al., 1993, 2000), although mammography identified smaller tumors than physical examination did. The study does not question the assertion that mammography lowers breast cancer mortality, but the results suggest that a very careful standardized physical examination (lasting an average of 10 minutes) can achieve the same reduction in mortality as screening mammography. The investigators in that study did not address the question of whether mammography led to reduced morbidity as a result of less aggressive treatment for the smaller tumors found by that screening approach. This is the only study to date to directly compare CBE to screening mammography, so there are no data to confirm or refute the findings, although the undertaking of such a confirmatory study has recently been suggested (Mittra et al., 2000). However, even if the data are sound, it might be more difficult in practice to recapitulate the benefits of CBE observed in this clinical trial (that is, more difficult than it would be for mammography) because mammography is highly standardized and regulated in the United States (see the discussion of the Mammography Quality Standards Act below), whereas CBE is not. A number of recommendations for improving the practice and standardization of CBE have been made based on a review of the literature (Barton et al., 1999).
Written and revised by
Gerald Hurowitz, M.D.
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Nevertheless, physical examination will always be important, but it is not sensitive enough to identify very small tumors. Although a pad to help women perform BSE was recently approved by the FDA and some electronic palpation devices are under development, prospects for improving physical detection methods may depend more on increasing the number of people who do it carefully and thoroughly after training and education than on technological advances.
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Screening mammography is promoted as the key to the continued reduction in breast cancer mortality through early detection. A number of organizations, including the National Cancer Institute (NCI), the American Cancer Society (ACS), and the American College of Radiology , currently recommend routine screening every 1 to 2 years for women over age 40 (U.S. Preventive Services Task Force, 1996). Several randomized controlled studies have been undertaken in four countries to assess the value of screening mammography (reviewed by Moss [1999] and Jatoi [1999]) (Table 1-2). Most of them demonstrated a substantial reduction in rates of death from breast cancer (about 25 to 30 percent) among women screened by mammography, and meta-analysis has confirmed a clear benefit of screening mammography for women over age 50 (Kerlikowske et al., 1995; Kerlikowske, 1997). (A recent review published in The Lancet criticized six of the eight trials for methodological inadequacies in randomization procedures that led to baseline imbalances and for determining the cause of death without blinding [Gotzsche and Olsen, 2000].
TABLE 1-2Results of Randomized Clinical Trials of Screening Mammography NOTE: RR, relative risk (a value less than 1 indicates fewer breast cancer deaths among screened women); CI, confidence interval, NBSS, national breast screening study. a Compared mammography plus CBE with no screening. b Compared mammography plus CBE with CBE alone (all others compared mammography with no screening). SOURCES: adapted from Jatoi (1999), Kerlikowske et al. (1995), and Moss (1999).
The authors concluded that because the two studies without these problems showed no reduction in mortality rates for the screened groups, screening for breast cancer by mammography is unjustified. An accompanying editorial and several letters to the editor rebutted the review, pointing out that the baseline differences were very small, that many other criteria are important for the assessment of screening trials, and that one trial did not assess screening but, rather, compared two different methods of screening.) The reported reduction in breast cancer mortality among women aged 40-49 appears to be less than that of older women, with a longer time period between initiation of routine screening and observation of reduced mortality. As a result, the value of screening women younger than age 50 is still controversial, as will be discussed later in this section.
There are now a variety of venues for mammography breast cancer screening, including doctors' offices, private radiology practices, hospital radiology departments, imaging centers, breast clinics, and mobile mammography vans. Because the effectiveness of screening mammography is dependent on the quality of the facilities and personnel, a federal law requires all mammography facilities to be certified by FDA. The intent of the Mammography Quality Standards Act (MQSA) was to ensure that all facilities meet federal standards for equipment, personnel, and practices.
TABLE 1-2Results of Randomized Clinical Trials of Screening Mammography
NOTE: RR, relative risk (a value less than 1 indicates fewer breast cancer deaths among screened women); CI, confidence interval, NBSS, national breast screening study. a Compared mammography plus CBE with no screening. b Compared mammography plus CBE with CBE alone (all others compared mammography with no screening). SOURCES: adapted from Jatoi (1999), Kerlikowske et al. (1995), and Moss (1999).
TABLE 1-3Mammographic Diagnostic Assessment Categories (Breast Imaging Reporting and Data System) – BIRADS SOURCE: American College of Radiology: Breast Imaging Reporting and Data System (BIRADS). Reston, Virginia, American College of Radiology, 1998.
Since its inception, the quality of mammograms has improved (Suleiman et al., 1999; U.S. General Accounting Office, 1998a,b; Wagner, 1999). However, mammography is the only medical examination that is federally regulated in this way, and the regulations substantially increase the cost of performing mammography (Inman, 1998; Wagner, 1999).
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A screening mammogram actually consists of two X-ray films, taken from the side (referred to as the "mediolateral oblique view") and from above (referred to as the "craniocaudal view"), for each breast. A diagnostic mammogram, which may include additional views or magnifications, is usually performed following a suspicious finding on a screening mammogram or when a woman has a new symptom such as a breast lump. To create a uniform system of assessing mammography results, the American College of Radiology developed the Breast Imaging Reporting and Data System (BIRADS) (Table 1-3). This system includes five categories of assessment with increasing suspicion of malignancy, along with standard follow-up recommendations for each category.
Ultimately, mammograms do not detect cancer per se. Rather, they provide a means for the identification of tissue abnormalities, which are subject to interpretation by human observers who introduce variability into the process on the basis of their prior experience, training, perceptual capabilities, vigilance, and so on. Radiologists look for microcalcifications (tiny calcium deposits), architectural distortions, asymmetrical densities, masses, and densities that have developed since the previous mammogram. In some cases, breast ultrasound may be ordered as a follow-up to mammography to rule out cysts (fluid-filled lesions) or to better characterize the lesion and its solid components. For women with a BIRADS score of 4 or 5, biopsy and histological examination are generally necessary to determine whether the abnormality identified by imaging methods is benign and harmless or malignant and life threatening.
Traditionally, a diagnostic biopsy entails an open surgical incision to remove a lump or tissue sample. In the case of nonpalpable lesions, the surgeon may be guided to the position of the abnormal tissue by "wire localization," in which a fine wire is inserted into the suspicious area and placement of the tip is confirmed by mammography. More recently, two minimally invasive biopsy methods have been developed for breast cancer diagnosis: fine-needle aspiration (FNA) for cytology and core-needle biopsy (CNB) for pathological assessment of breast tissue (Fajardo and DeAngelis, 1997; Morrow, 1995; Scott and Morrow, 1999; Sneige, 1991). A very thin needle and syringe can be used to remove either fluid from a cyst (standard FNA) or clusters of cells from a palpable mass (fine-needle aspiration biopsy [FNAB]). It is most frequently used to confirm a cyst by removing the cyst fluid. If the mass proves to be solid or only partially filled with fluid, the needle is quickly pushed back and forth through the solid tissue while suction is applied to free some cells, which are aspirated and analyzed by a cytopathologist. The sensitivity of FNAB cytology depends on the quality of the sample obtained and the experience of the cytologist, but it generally falls in the range of 65 to 98 percent (Scott and Morrow, 1999). Unfortunately, the ability to obtain samples of sufficient size from nonpalpable lesions is limited, and the retrieval of such samples can be done only with imaging guidance (ultrasound or mammography).
Thus, FNA is not as useful in such instances (Pisano et al., 1998b). Other limitations of this procedure are that it cannot distinguish between invasive cancer and in situ lesions, and it may produce inconclusive findings that require an additional core or open biopsy procedure.
CNB, although more traumatic for the patient, affords a higher rate of sensitivity. CNB uses a larger needle with a special cutting edge. The needle is inserted, under local anesthesia, through a tiny incision in the skin, and 5 to 10 small cores of tissue are removed. Tissue cores obtained by CNB are usually sufficiently large to allow pathologists to distinguish between invasive and noninvasive types of breast cancer. For nonpalpable lesions, CNB must be combined with an imaging modality (X ray, ultrasound, or less frequently, MRI) to target the suspicious tissue. The choice of guidance method depends on the experience of the radiologist or surgeon, the equipment available, and the type of lesion.
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Novel CNB systems are also being developed with the goal of improving accuracy (Velanovich et al., 1999; Wong et al., 2000). One example is a vacuum-assisted biopsy instrument, also known as a Mammotome, in which suction is applied to the tissue while CNB is performed.
This results in more tissue being drawn into the needle. In one study that compared standard stereotactic CNB with vacuum-assisted biopsy in patients with microcalcifications, CNB missed calcifications in nearly 10 percent of the patients, but vacuum-assisted biopsy did not miss calcifications in any of the 106 patients (Meyer et al., 1997). The Advanced Breast Biopsy Instrument (ABBI) is an example of a new system for removal of a larger core biopsy specimen than is possible with a Mammotome or by traditional CNB. The ABBI method uses a rotating circular knife and a thin wire heated with an electrical current to remove a large cylinder of tissue containing the abnormality.
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Sharyl J. Nass, I. Craig Henderson, and Joyce C. Lashof
Committee on Technologies for the Early Detection of Breast Cancer
National Cancer Policy Board INSTITUTE OF MEDICINE and Division of Earth and Life Studies NATIONAL RESEARCH COUNCIL
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