May 4, 2011

Screening Mammography Finds Smaller, Less Invasive Tumors

Breast tumors that are detected on screening mammography in women between 40 and 49 years of age are smaller and are less likely to have nodal metastases compared with tumors found on physical examination. Results of a study showing this were presented here at the American Society of Breast Surgeons (ASBrS) 12th Annual Meeting.

Paul Dale, MD, from the University of Missouri, Columbia, and colleagues found that breast tumors detected on screening mammography in women between the ages of 40 and 49 years were significantly smaller, at approximately 2 cm, compared with breast tumors identified by physical exam, at approximately 3 cm (P < .0001). Sentinel lymph nodes were also positive in only 25% of tumors detected on screening mammography compared with 56% of tumors detected on clinical examination (P < .0001).

At 5 years, 94% of women whose breast cancer was detected on screening mammography were still free of disease compared with 71% of those whose tumors were not detected by mammography, whereas overall survival (OS) at 5 years was also higher, at 97% in the mammographically detected tumor group compared with 78% for the nonmammographically detected group.

“The revised Preventative Service Task Force [USPSTF] mammography guidelines exclude women between 40 and 49 from routine mammography and will potentially result in later disease diagnosis and poorer survival rates for this age group of women,” Dr. Dale said at a press conference here. “Our study found that tumors identified through mammography generally had better outcomes after treatment than those found through clinical exams.”

Systematically Reviewed

For the study, investigators identified women between the ages of 40 and 49 years who were treated for breast cancer at their tertiary care center between 1998 and 2008. Women were divided into those who had mammographically detected cancers or cancers that were detected clinically, not by mammographic screening. Of some 1581 women treated for breast cancer at the tertiary center during the 10-year study interval, 320 women, or 20% overall, were between the ages of 40 to 49 years, as Dr. Dale pointed out.

Nine patients were excluded from the study because of incomplete records, leaving 145 women who had mammographically detected cancers and 166 women who had nonmammographically detected cancers.

Table.

Mammographically Detected Cancers (n = 145) Nonmammographically Detected Cancers (n = 166)
Tumor size (mm) 20.68 30.38
SLN positive 24.7% 55.9%
5-year DFS 94% 71%
5-year OS 97% 78%

Related Study

In a related study, Sharon Lum, MD, from the Loma Linda University School of Medicine in California, identified 46,691 patients between the ages of 40 and 74 years who were diagnosed with ductal carcinoma in situ (DCIS) or early invasive breast cancer (T1N0) between 2004 and 2008. Both DCIS and T1N0 breast tumors are more likely to be detected on screening mammography, as Dr. Lum pointed out. All patients had records in the California Cancer Registry.

Of this large cohort, 22.6% of patients were between the ages of 40 to 49 years, whereas 77.4% were between the ages of 50 to 74 years, “meaning that nearly one quarter of women in our study population would have been excluded from screening mammography [because of their age],” Dr. Lum added.

Results showed that women between the ages of 40 and 49 years who had DCIS were more likely to have hormone receptor–positive breast cancer compared with women between the ages of 50 and 74 years.

Younger women with T1N0 also were more likely to have hormone receptor–positive tumors compared with older women, as well as to be HER-2 positive than older women and to have triple-negative disease. Dr. Lum also observed that younger women with DCIS were more likely to be of Hispanic and Asian/Pacific Islander race or ethnicity, whereas those with early invasive tumors were also more likely to be from a Hispanic, non-Hispanic black, or Asian/Pacific Islander background.

Odds Ratios for Women Aged 40 to 49 Years vs Women Aged 50 to 74 Years

DCIS TIN0
Hormone receptor positive 1.85 1.43
HER-2 positive NA 1.46
Triple negative NA 1.67
Hispanic 1.62 1.82
Asian/Pacific Islander 1.50 1.66

“Excluding 40- to 49-year-old women from screening could impact on the early diagnosis of hormone receptor–positive, HER-2, and triple-negative breast cancer and potentially lead to lost opportunities for targeted therapies in early-stage disease,” Dr. Lum emphasized. “[A]nd the adoption of these recommendations would disproportionally affect nonwhite women and potentially lead to a more advanced stage [of] disease at the time of presentation.”

In commenting on both studies, American Society of Breast Surgeons’ Spokesperson Deanna Attai, MD, from the Center For Breast Care, Inc, in Burbank, California, toldMedscape Medical News that society cannot ignore the fact that women between the ages of 40 and 49 years develop breast cancer at a not-insignificant rate.

“We are not talking of 1 or 2 patients here, we are talking about a fair number of patients. What was striking was that investigators really did show that women who did not undergo mammography had larger tumors, were more likely to have positive lymph nodes, and had poorer overall survival,” she said.

“I think this is important news, and we are going to see more and more studies coming out that will continue to show the benefit of screening mammography in younger women,” Dr. Attai said.

The American Cancer Society, the American College of Surgeons, and the American Society of Breast Surgeons all continue to recommend routine screening mammography for women older than 40 years.

Despite this, a study to be presented at the American Roentgen Ray Society 2011 Annual Meeting has found that the USPSTF recommendations have already begun to affect the number of yearly mammograms done in women between 40 and 49 years of age. Compared with the previous year, Lara Hardesty, MD, from the University of Colorado in Denver, counted 205 fewer women in the 40- to 49-year age group who underwent screening mammography in the 9 months after the USPSTF guidelines.

“We must continue to get the message out to our patients and make sure that referring providers understand our recommendations because they are the ones who are influencing patients in that age group,” Dr. Hardesty said in a news release.

Partial support for Dr. Lum’s study came from the National Cancer Institute. Dr. Dale, Dr. Lum, and Dr. Attai have disclosed no relevant financial relationships.

American Society of Breast Surgeons (ASBrS) 12th Annual Meeting: Abstracts 1670 and 1754. Presented April 29, 2011.

— Pam Harrison

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