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Feb. 23, 2012
Feb. 23, 2013
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By Charles Bankhead, Staff Writer, MedPage Today
Published: February 23, 2012
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco.
Mammography-detected breast cancers in women 40 to 49 doubled from 1990 to 2008, coinciding with a significant reduction in stage at diagnosis and significant improvement in survival, a Seattle study showed.
The frequency of mammography-detected breast cancer increased from 28% to 58%, whereas physician- and patient-detected cancers decreased from 72% to 42% (P0.001).
Use of mastectomy declined by 50%, and the frequency of breast-conserving surgery increased by 40%.
Five-year relapse-free survival (RFS) increased significantly from 88% to 92% (P0.001), as reported in the March issue of Radiology.
“The shift over time in our cohort to increasing incidence of mammography-detected breast cancer has the same trajectory as national self-reported rates of participation in screening programs,” Judith A. Malmgren, PhD, of HealthStat Consulting in Seattle, and co-authors wrote in their discussion.
“Women aged 40 to 49 years whose breast cancer was detected with mammography received a diagnosis at an earlier stage than would be possible without mammography, allowing for less invasive surgery and less toxic chemotherapeutic treatment and accompanied by a lower rate of recurrence and disease-related mortality,” they said.
However, they stressed that because of the prospective cohort study design, they cannot “directly comment on causal relationships.”
Still, the results add another chapter to the ongoing debate about screening mammography in women younger than 50. The U.S. Preventive Services Task Force (USPSTF) invited the debate when it decided in 2009 not to recommend regular mammography for women 40 to 49, and instead encourage women in that age group and their physicians to make individualized decisions.
Malmgren and co-authors referenced the USPSTF decision and ensuing controversy, noting that USPSTF concluded that the data showed “the net benefit [of mammography] is small for women aged 40 to 49 years compared with older women.”
The authors pointed out that the USPSTF reviewed a number of older studies, some of which had design flaws. They also reviewed several recent studies that have demonstrated a shift in breast cancer diagnosis to lower stages and to significant reductions in breast cancer mortality, coinciding with screening mammography in women younger than 50.
Malmgren and co-authors undertook an analysis to determine trends in breast cancer stage at detection, treatments, and outcomes in women 40 to 49. They retrospectively reviewed prospective data on 2,000 women who had biopsy-confirmed primary breast cancer (all stages) from 1990 to 2008 at Swedish Medical Center in Seattle.
The medical center’s cancer registry is updated annually, including information on recurrence, subsequent treatment, and vital status. The survival analysis included patients whose cancer was diagnosed through 2006, allowing for a minimum of two years of follow-up in all cases.
The percentage of mammography-detected breast cancers ranged between 28% and 43% during 1990 to 2000, ?40% during 2001 to 2004, and ?50% from 2005 to 2008 (P0.001 for trend). The detection rate increased significantly in the subgroup of women ages 40 to 44 and the subgroup of women 45 to 49 (P0.001).
Physician-detected cancers increased from 1.5% of breast cancers in 1991 to a high of 12.8% in 1996 before decreasing to 10% for 1997 to 2008.
The tumor diameter for mammography-detected breast cancer averaged 1.80 cm versus 2.98 cm for tumor detected by patients or physicians (P0.001).
The data revealed a significant shift in stage at diagnosis, as the proportion of stage 0 cancers increased from about 10% annually during 1990 to 2002 to 30% in 2008; stage I and II, 30% to 40%, with a trend to more stage I diagnoses during the last five years; and the proportion of advanced-stage tumors at diagnosis decreased from 24% in 1990 to 8% in 2008 (P0.001).
“The increase in stage 0 cancers was exclusively among mammography-detected cases,” the authors wrote.
An unadjusted analysis showed that 67% of patients with mammography-detected breast cancer underwent lumpectomy, compared with 48% of cancers detected by patients or physicians. The mastectomy rate was 25% for mammography-detected tumors versus 47% for all others.
More patients with physician- or self-detected cancers underwent surgery and chemotherapy (22% versus 13%) or surgery, radiation therapy, and chemotherapy (60% versus 32%, P0.001).
Survival analyses demonstrated a consistent advantage for mammography-detected cancers, including:
- Five-year RFS, 92% versus 88%
- 10-year RFS, 89% versus 81%
- Five-year disease-specific survival (DSS), 95% versus 91%
- 10-year DSS, 93% versus 88%
- Five-year overall survival (OS), 97% versus 93%
- 10-year OS, 91% versus 85%
The study did have limitations: It was not an evaluation of a mammography screening program. Also, the method of detection was from a chart review as reported by the treating physician.
“The objective of screening is to detect disease at an earlier more treatable phase, which, from our review, mammography accomplishes,” the authors concluded. “The evaluation of mammographic screening should include treatment reduction and not concentrate solely on mortality reduction.”
The study was supported by the Kaplan Cancer Research Fund, Fred Hutchinson Cancer Research Center, and National Cancer Institute.
Malmberg had no disclosures. Co-authors disclosed relationships with Hologic and World Class CME.
Primary source: Radiology
Malmberg JA, et al “Impact of mammography detection on the course of breast cancer in women aged 40 to 49 years” Radiology 2012; 262: 797-806.
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Article source: http://www.medpagetoday.com/HematologyOncology/BreastCancer/31335