Palpable Breast Cancers More Common in Women Not Having Annual Mammography

From Medscape Medical News
Laurie Barclay, MD

March 26, 2010 — Palpable breast cancers are more common in women not having annual mammography, according to the results of a study reported in the March issue of the Journal of the American College of Surgeons.
Despite the frequent use of screening mammography, 43% of breast cancers presented symptomatically or as a palpable mass.

"This study confirms the importance of participation in screening mammography, since a palpable presentation was least common in women undergoing mammographic screening at the recommended interval of 1 year," senior author Amy C. Degnim, MD, FACS, associate professor of surgery at the Mayo Clinic in Rochester, Minnesota, told Medscape Ob/Gyn & Women's Health.
"In addition, this study sheds light on the possible impact of reduced breast cancer screening with mammography for women between [the ages of] 40 and 49 [years], as recently recommended by the US Preventive Services Task Force [USPSTF].
Lastly, this study shows that some cancers are still detected by breast self examination [BSE] and by clinical breast examination [CBE] by a healthcare provider, so there is still a role to be defined for these techniques in detecting breast cancer."

A study by the Commission on Cancer in the 1990s showed that the percentage of breast cancer patients presenting with palpable masses decreased from over 70% in 1983 to 44% in 1990, which may be attributable to the increasing use of screening mammography. Before the present study, however, few data have been published since 1990.

Breast Cancer Screening Recommendations

The new findings fuel the controversy over breast cancer screening recommendations. On November 17, 2009, the USPSTF issued new breast cancer screening guidelines recommending against routine mammography screening for women younger than age 50 years and for stopping screening at age 74 years. On the basis of current evidence, the USPSTF also could not determine the additional benefits and harms of CBE beyond screening mammography in women 40 years or older and recommended against teaching BSE.

"[Our] study demonstrates that the recent USPSTF recommendations should be taken with caution," Dr. Degnim said.

After widespread objections to the USPSTF guidelines by the American Cancer Society (ACS), the American College of Radiology (ACR), and others, the ACR and the Society of Breast Imaging jointly issued new recommendations in January 2010.

These guidelines on the use of imaging modalities for breast cancer screening suggest that women at average risk of developing breast cancer should begin annual mammography screening at age 40 years.

"Compared with detection by mammography, palpable breast cancer is larger, more likely to have metastasized, and have worse prognosis and worse survival," Robert A. Smith, PhD, ACS director of cancer screening, told Medscape Ob/Gyn & Women's Health.
"Mammography is the single best tool we have for the detection of breast cancer when it is small, has not spread, and when treatment options are greatest."

"Women with palpable tumors have larger tumor sizes and more advanced stage at presentation," Dr. Degnim agreed. "They also have worse breast cancer–specific survival than those with mammographically detected cancers, even when adjustments are made to compare women with similar tumor size and nodal stage."

Study Findings

The goal of the present study was to determine the method of cancer detection and frequency of screening mammography in women undergoing breast cancer surgery in 2000, using an institutional surgical breast cancer database from the Mayo Clinic. The investigators reviewed medical records to evaluate presentation at time of diagnosis and to characterize it either as "palpable" if the woman presented with a breast complaint or if a new mass was identified on examination or as "screening" if breast cancer was detected on screening mammography.

Dates of prior mammography screening were also recorded, and patients whose cancer was detected by mammogram were compared with those whose tumors were detected by BSE or CBE. Of 592 breast cancers detected, 335 (57%) were identified on screening, 255 (43%) were characterized as palpable, and in 2 patients (<1%), the method of cancer detection was unknown.

In women with a palpable mass, the size of the tumor was significantly larger than in women in whom cancer was detected by mammography (2.6 vs 1.5 cm; P < .0001). Patients with palpable presentation were younger than those with screen-detected cancer (mean age, 57 vs 62 years; P < .0001).

"The study findings are consistent with what is known about the advantage of mammography in detecting breast cancer before it has reached a size when it is palpable; that is, the screen-detected cancers were smaller than the palpable cancers," Dr. Smith said. "The cancers detected on mammography also were less likely to be advanced; that is, not having spread to the axillary lymph nodes. The findings also show that some women will, inevitably, be diagnosed with a palpable tumor before they are due for their next mammogram."

At least 1 prior screening mammogram was documented in 481 women (81%), although most screenings were performed less frequently than once annually. Compared with women who had previous mammography, those who had no previous screening mammography were more likely to have cancer present as palpable (67% vs 39%; P = .0002).

"We know that mammography does not pick up every breast cancer, however we were surprised at how often breast cancer was detected by a palpable mass," coauthor Judy Boughey, MD, FACS, an assistant professor of surgery at Mayo Clinic, said in a news release. "Presentation as a palpable mass was more frequent in those women who had not had a mammogram in the prior 12 months. This finding is even more concerning when you consider the recent recommendations for decreasing the use of mammography because it would result in an even greater proportion of breast cancers being detected by palpation and therefore at more advanced stages."

On the basis of their findings, the study authors concluded that despite the frequent use of screening mammography, 43% of breast cancers presented as a palpable mass or otherwise symptomatic presentation, whereas 57% were detected by mammography. Women who had not had mammography were more likely to present with palpable tumors.

Carol H. Lee, MD, radiologist from the Memorial Sloan-Kettering Cancer Center in New York City, and chair of the ACR Breast Imaging Commission, told Medscape Ob/Gyn & Women's Health that these findings were "not particularly surprising."

"The cancers found by screening were smaller, and it is known that smaller, lower-stage cancers are associated with a better prognosis," Dr. Lee said. "In addition, for cancers of similar size, those that are not palpable cancers have been shown to have a better outcome. In my opinion, this study emphasizes the importance of both screening mammography and BSE and underscores the potential damage that might occur if the USPSTF guidelines are widely followed in terms of delay in breast cancer diagnosis."

Study Strengths and Limitations

"A strength of this study is that it evaluates the frequency of palpable presentation of breast cancer in the modern era, during a time in which screening mammography was widely used, so this is likely very reflective of the current pattern of how breast cancers are discovered," Dr. Degnim said. "Another strength of this study is that the method of presentation could be determined for the vast majority of patients from the medical records, whereas this detailed information is usually not available in large national databases."

"[This study] is informative about the recent screening experience of women with a palpable mass vs those whose breast cancer was detected on mammography, and the tumor characteristics of each group," Dr. Smith said. "It also is informative about the mode of detection among women who had a palpable breast cancer, although there may be a lack of precision between categories of [BSE], incidental breast cancer detection, and 'found by patient, but method unspecified.' "

However, Dr. Smith also noted that the findings are not generalizable to the larger population of women beyond those presenting to the Mayo Clinic in Rochester for breast cancer surgery in 2000, and that the study depended on retrospective chart review for evidence of frequency and data of prior screening.

The study authors agree that these factors limitgeneralizability and also note that the study was set at a tertiary referral center, where patients might be more likely to present with palpable or more advanced tumors, and that the study population was almost exclusively white. These data were from 2000, when only film mammography was used, whereas the current practice is to use digital mammography.

"This study is a case series; it does not appear to be designed to study associations or causalities, and therefore the authors' conclusions are not appropriate because the results are calculated based on events (ie, mammogram vs SBE) that occurred in their cases," Miriam Alexander, MD, MPH, director, General Preventive Medicine Residency, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, told Medscape Ob/Gyn & Women's Health when asked for independent comment. "They were not able to use any measures of association such as odds ratios or relative risks, as this was not a case-control or cohort study or a clinical trial. I do not believe there are epidemiological or statistically valid conclusions that can be drawn from their results; they can only fairly report their results as observations of occurrence."

"I do not believe that studies like this would be considered by the USPSTF in evaluating whether the evidence is supportive, not supportive, or insufficient for screening tests such as mammography or SBE," Dr. Alexander said. "Unfortunately, there are no conclusions that can be drawn from this study as to the use of mammography or SBE for screening. Therefore, I cannot see that there are any clinical implications for changing screening recommendations based on this study."

Research Recommendations

In terms of additional research, Dr. Lee recommended continuing to develop more sensitive imaging methods to detect early breast cancer.

"The study implications remain valid for clinical practice today, since there have not been dramatic changes in participation in screening mammography over the last 10 years," Dr. Degnim said. "Further research is needed to evaluate whether this finding remains true in 2010 and in community-based healthcare settings."

Dr. Smith pointed out that we need to learn more about the duration of time between the first detection of a palpable mass and when women report symptoms to their physician. Although he believes this time is shorter today than in 2000, he suggests that factors contributing to the detection of palpable breast cancer and either quick reporting or delay need to be better understood.

"I do not believe that the results of this study should contribute to clinicians' decision making," Dr. Alexander said. "It is totally appropriate and necessary to continue our quest to minimize the human burden of suffering from breast cancer, but I would not recommend that further research be undertaken along these lines if our goal is to correctly identify and treat significant disease on a population basis.

"If we want to appropriately identify breast cancer from other breast anomalies, and if we want to correctly identify breast cancers that need treating to prevent morbidity and mortality, we should do research to develop tests or methodologies that meet all the criteria for excellent screening tests," Dr. Alexander continued. "There are multiple study designs that could then be employed to demonstrate the strength of the association between the screening test in question and the reduction in disease or its severity or progression, depending on the goals of the researchers."

Detection by BSE

Among the 255 patients with palpable or otherwise symptomatic presentations, 86% of the cancers were found by the patient either incidentally or during BSE, and the remaining 14% were detected during CBE by a physician or other healthcare provider.

"Because we don't know what proportion of women in the sample actually performed routine BSE, we can't conclude anything about the performance of BSE in detecting palpable tumors, nor did the authors report the relative sizes of the palpable tumors that fell into each group," Dr. Smith said. "The finding that CBE accounted for a very small proportion of the detected palpable breast cancers is consistent with recent literature [and]...is consistent with the observation that most women don't practice regular BSE. The ACS does not recommend for or against routine BSE but does emphasize the importance of maintaining a heightened sense of awareness about the presence or absence of breast symptoms."

Clinical Implications

The study authors note that their findings reaffirm the importance of participating in regular screening mammography, because this was associated with a decreased frequency of palpable presentation that was lowest among those women screened at the recommended annual interval. They also suggest that their findings confirm that both BSE and CBE still play a role in detecting breast cancer.

Dr. Smith noted that 71% to 75% of breast cancers diagnosed in the period between 11 and 24 months were detected by mammography screening, which highlights the greater advantage of annual screening vs biennial screening.

"Breast cancers are missed due to human error or because of the limitations of the exam in women with significant breast density," he said. "However, [the study findings] are consistent with the observation that there is a greater likelihood of detecting a palpable tumor the longer the duration from the previous mammogram, but also that mammography is not perfect and that some breast cancers will arise in the period between normal screening exams."

When asked how findings from this study affect ACS' position concerning the recent USPSTF recommendations regarding screening mammography, BSE, and CBE, Dr. Smith responded, "There is clear evidence that mammography saves lives in women 40 years of age and older. As these data show, women at all ages who were detected with a palpable mass were more likely to have a more advanced breast cancer compared with women with breast cancer detected by screening."

Although a higher proportion of women between ages 40 to 49 years were diagnosed with a palpable mass (58% vs 42%), a majority of women older than 40 years who had never had a previous mammogram were between the ages of 40 and 49 years. Dr. Smith noted that among women with prior screening, the risk of being diagnosed with a palpable tumor may have been more similar in younger and older women.

The study showed that a sizeable percentage of breast cancers occurred in women in their 40s (namely, 19%), leading the study authors to state that "Without screening mammography in this age group, at least 48 of these 115 cancers would have been missed, and many more would likely have been missed if both CBE and [BSE] were also omitted."

"In this instance, 'missed' means that these women would have been diagnosed with palpable breast cancer, had worse prognosis, fewer treatment options, and most likely poorer survival," Dr. Smith concluded. "Although ACS recommends routine CBE, we recognize its diminishing contribution to the detection of palpable breast cancer as routine mammography and a heightened sense of awareness account for most breast cancer detection."

Dr. Degnim and the other study authors and experts have disclosed no relevant financial relationships.

J Am Coll Surg. 2010;210:314-318. Abstract