How do breast cancer mortality rates differ between women who are screened annually and biennially by mammography?


Scientific Study, 2015
17 Pages

Excerpt

Table of Contents

Abstract:

Introduction

Methods

Results

American Cancer Society Guidelines for Early Breast Cancer Detection, 2003 8

U.S. Preventive Services Task Force guideline for early breast cancer detection, 200210

Discussion

Conclusion:

Reference

Abstract:

Context: Breast cancer is the most common non-skin cancer and second deadliest cancer in women. Mammography, an X-ray of the breast, serves as the primary diagnostic tool for breast cancer detection as it reduces the risk of death through early detection and treatment of the disease. The medical community, however, has not agreed on how frequently such screenings should be performed. 3 Various organizations have produced different guidelines regarding the suggested frequency of routine mammograms. For example, the United States Preventive Services Task Force (USPST) endorses biennial mammography screenings for females ages 50-74, whereas the American Cancer Society (ACS) advocates annual mammography screenings for women beginning at age 40. It is this review’s hypothesis that annual mammography is proving to be statistically more beneficial than biennial screening in the reduction of breast cancer mortality rate.

Methods: Full text articles from the U.S. National Institute of Health’s Public Medicine’s archives (PubMed) were reviewed in order to compare annual versus biennial mammographic screenings and the diagnostic advantages, detriments and mortality rates of each interval.

Results: The majority of articles agree that women between the ages of 40-49 years undergoing biennial screenings are more likely to be diagnosed with late stage disease than women diagnosed during annual screenings. The results for women 50 years and older are less conclusive. While some studies of the over-50 group delineate no difference in the incidence of late-stage disease using either the biennial or annual intervals, the majority of findings suggest the annual interval is more effective than the biennial screening in detecting early stage cancer.

Conclusion: Overall, women partaking in annual mammography screening experience decreased false positive “recall” rates. In addition, earlier diagnoses through annual screenings help detect smaller tumors providing a more hopeful prognosis. While these findings support the importance of annual mammography screenings for women 40 years and older, studies indicate that annual screenings only minimally improve estimated breast cancer survival rates for women aged 50-74 years compared to biennial screening.

Keywords: Breast cancer, screening program, mortality rate, statistics, annual, biennial, frequency, mammography, Risk, American Cancer Society, United States Preventive Services Task Force, late stage breast cancer

Introduction

Breast cancer remains one of the most life-threatening diseases facing American women. Citing the Center for Disease Control and Prevention statistics, approximately 210,000 breast cancer cases and 40,000 breast cancer deaths were reported in 2008.9 Current statistics show that one in every eight women is diagnosed with breast cancer within her lifetime, and one in every 30 women dies as a result of the disease.9

Breast cancer remains the second most common malignancy in females after skin cancer. The disease, which originates either in the ducts or the lobules of the breast, can occur in both human sexes. Two primary categories of breast cancer exist: invasive and non-invasive.7 The Ductal and Lobular Carcinomas, DCIS and LCIS respectively, are the subtypes of non-invasive breast cancer, while Invasive Ductal Carcinoma (IDC) and Invasive Lobular Carcinoma (ILC) are the major subtypes of invasive breast cancer.7

Breast cancer incurrence rates have been associated with three main factors in female patients: advanced age, lower socioeconomic status, and lower education level. Other risk factors associated with the incidence of breast cancer include genetic predispositions, obesity, the use of hormone replacement therapy, and alterations in procreative patterns, for example, the bearing of children at an advanced age or bearing no children. Despite continuing improvements in the diagnosis of breast cancer, over half of the malignancies occur in females whose risk factors are not clinically identifiable.

Breast cancer mortality rates in the United States peaked between the years 1986 to 1991, reaching a high 34% rate. By the year 2007, the number of breast cancer deaths in the United States had dropped to 22%, representing a significant 30% decrease.1 This reduction in mortality rates is generally associated with the increasing popularity of mammography screening in the 1980s.1 The medical community references this statistical drop as indicating a strong correlation between early detection via mammograms and improved breast cancer survival rates.

Mammography is generally considered the best diagnostic tool for breast cancer detection. However, the medical community still does not agree on how frequently mammograms should be conducted. Different organizations have released different guidelines regarding the frequency of routine mammograms. For instance, the United States Preventive Services Task Force (USPSTF) endorses two-yearly mammography screening for females between the ages of 50 - 74 years while the American Cancer Society (ACS) advocates for annual mammography screenings beginning at age 40. The lack of consensus regarding optimal frequency for this cancer screen may limit the options available for women seeking earliest detection and treatment. This research attempts to provide significant analysis of the effectiveness of frequency rates, which may lead to lower breast cancer mortality rates.

Different malignancy rates among American women, 1930-2006. The graph shows no significant change in mortality from 1930-1990, after which a noticeable decline begins to occur through 2006. (Reprinted from Jemal A, Siegel R, Xu J, Ward E, Cancer statistics, 2010. CA: A Cancer Journal for Clinicians, n/a. doi:10.3322/caac.20073)

Methods

Database searched included PubMed, Clinical Queries, Medscape, E-medicine, ACS, USPSTF, Evidence Based On Call, Scientific Electronic Library online, and Google Scholar.

Keywords to search included the following MeSH (medical search) terms: Breast cancer, screening program, mortality rate, statistics, annual, biennial, frequency, mammography, Risk, American Cancer Society, United States Preventive Services Task Force, late stage breast cancer

Publication dates were limited to within the last 15 years; one Canadian published article was utilized.

Study population: Humans, Adult Females

Results

In 2003, the ACS rationalized its guiding principles for early detection of breast cancer on recommendations from acknowledged scientific evidence and research findings. The ACS’s most recent screening endorsements include data gathered from test mammography, bodily checkup, the testing of elderly women and women suffering from comorbid disorders, the screening of high-risk females, and precise screening methods .8 A summary of the current ACS guidelines appears in the table below:

American Cancer Society Guidelines for Early Breast Cancer Detection, 2003 8

U.S. Preventive Services Task Force breast cancer screening guidelines

In 2002, the U.S. Preventative Task force, an independent panel of non-Federal experts in prevention and evidence-based medicine, updated the guidelines and recommendations for breast cancer screening. A summary of these guidelines is shown in the table below:

U.S. Preventive Services Task Force guideline for early breast cancer detection, 200210

A retrospective review cohort study was conducted by Hunt et al. (1999), analyzing over 24,200 women aged 40-79 years in six counties in the San Francisco area between April 1985 and August 1997.5 The study’s purpose was to determine whether annual or biennial mammography best served the public preventative health efforts.5 The California University San Francisco Medical enter provided a mobile mammography van to screen previously asymptomatic patients.5

The collected outcome measures were compared retrospectively for women who underwent annual versus biennial screening mammography.5 Annual screenings were defined as mammography screenings performed between 10-14 months, and biennial screening included mammography screenings performed between 22-26 months.5 Screening examinations involved a medio-lateral oblique and cranio-caudual mammographic view of each breast.5 These examinations were interpreted by board-certified staff radiologists and the interpretations were reported as normal or abnormal.5 Clinical outcomes for all women with screening examinations interpreted as abnormal were determined by contacting each women’s personal physician and by searching the institution’s radiology and pathology database.5 This procedure enabled the researchers to determine the rates of recall, biopsy, and cancer detection for annual screening and biennial screening cohorts as well as the tumor size, lymph node status, and stage of the cancer.5 A chi-square test was used to compare the rates of recall, biopsy, screening-detected cancer, and stage of the cancer.5 The Mann-Whitney test was used to asses difference in the size of cancers.5

The results are as follow: 518 annual screening recall versus 160 biennial screening recall. 5 The annual screening recall rates of 2.6% was 30% less than the biennial recall rate of 3.7% (P < .0001).5 150 annual screening biopsies were performed versus 45 biennial screening biopsies.5 The annual screening biopsy rate was 0.75%, 28% lower than the biennial screening rate of 1.0% (p = .06).5 Women who had annual mammography screening showed a significantly lower recall rate (p < .0001) and a lower biopsy rate that approached statistical significance (p = .06).5 Also the annual screening group exhibited 56% fewer interval cancer cases than those in the biennial screening group (p = .22).5

Cancer was detected in 71 women during annual screening versus 19 women in biennial screening.5 The ratio of screening-detected invasive cancer to ductal carcinoma in situ (DCIS) was almost identical for both cohorts: for annual screening, 75% invasive carcinoma and 25% DCIS; for biennial screening, 74% invasive and 26% DCIS.5 The annual screening cancer detection rate was 0.36%, representing a 19% reduction compared with the biennial rate of 0.44% (p = .49). 5 The median tumor size of combined screening-detected cancer was 11 mm, 27% smaller than the median tumor size of 15 mm within the biennial screening cohort (p = .04).5 The mean tumor size of the combined cancers in the annual cohort was 13.3 ± 0.95 mm compared with 18.0 ± 2.19 mm (p = .04).5 There were also 38% fewer cases of cancer with lymph node (LN) metastasis in the annual cohort group (9/62, 14%) compared with the biennial screening group(4/17, 24%). (p = .37).5 Evaluation of cancers for +2 stage resulted in 41% fewer cases of cancer in the annual group (14/81, 17%) compared with the biennial screening cohort group (7/24, 29%) (p = .20).5 Parallel increase in the cancer detection rate with advancing patient age were found within both cohorts.5

In addition, White, et al. (2004) conducted an observational study to investigate the effects of annual versus biennial mammography on late-stage breast cancer. The information used in the study was collected from the Breast Cancer Stakeout Confederation (BCBS) that included statistics on more than 4,000,000 mammograms and succeeding cancers.12 The women included in the study were diagnosed with invasive breast cancer or DCIS between January of 1996, and thirty first of December 2001, with an age range of 40-89 years.12 Annual screenings were defined as mammography screenings performed between 9-18 months, (median 13 months) and biennial screening were considered to be mammography screenings performed between 18-30 months (median 24 months).12 Information was collected by mammography registries that participate in the National Cancer Institute funded Breast Cancer Surveillance.12

Data was collected from 176 mammography facilities in seven sites across the United States. Information was obtained on the women’s demographic and breast cancer risk factors as well as the mammography results for each mammogram.12 Each mammography registry is linked to a regional Surveillance, Epidemiology, and End Results (SEER) program or to a state tumor registry that provides information on cancer occurrences, including screen-detected and interval-detected cancers.12 Five of the seven registries (the exceptions are those in California and Colorado) also link to pathology laboratory records.12 Data collected by all seven registries in the Breast Cancer Surveillance Consortium were included in the study: Carolina Mammography Registry, Chapel Hill, North Carolina; Colorado Mammography Project, Denver, Colorado; New Hampshire Mammography Network, Lebanon, New Hampshire; New Mexico Mammography Project, Albuquerque, New Mexico; San Francisco Mammography Registry, San Francisco, California; Vermont Breast Cancer Surveillance System, Burlington, Vermont; and Group Health Cooperative, Seattle, Washington.12 The survival rates of breast cancer patients were higher in women screened annually than those of women screened only once in two years.12

Cancer was detected in higher proportion in annual screenings, totaling 5400 women in annual screening versus 2440 women in biennial screening (74% versus 62%; P<0.001).12 Annual screening resulted in 20% DCIS and 80% invasive disease compared with biennial screening that resulted in 17% DCIS and 83% invasive disease.12 Annual screening resulted in 36% of tumors being less than 10 mm, 42% of tumors 11-20 mm and 22% larger than 20 mm, versus biennial screening which resulted in 33%, 43% and 24%.12 Both groups statistics do not add up to 100% due to missing information.12 Annual screening resulted in 36% of identified tumors being less than 10 mm, 42% of tumors 11-20 mm and 22% larger than 20 mm, versus biennial screening which resulted in respective sizes of 33%, 43% and 24% .12 Both groups’ statistics do not add up to 100% due to missing information.12

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Details

Title
How do breast cancer mortality rates differ between women who are screened annually and biennially by mammography?
College
Saba University School of Medicine  (Medical School)
Author
Year
2015
Pages
17
Catalog Number
V320377
ISBN (eBook)
9783668202887
ISBN (Book)
9783668202894
File size
795 KB
Language
English
Tags
Breast cancer, screening program, mortality rate, statistics, annual, biennial, frequency, mammography, Risk, American Cancer Society, United States Preventive Services Task Force, late stage breast cancer, Medical, medicine, health, malignancy, women's health
Quote paper
Amir Hossein Mortazavi Entesab (Author), 2015, How do breast cancer mortality rates differ between women who are screened annually and biennially by mammography?, Munich, GRIN Verlag, https://www.grin.com/document/320377

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