A review
Descrição do Produto
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A Review Obesity and Screening for Breast, Cervical, and Colorectal Cancer in Women
Sarah S. Cohen, MS1,2 Rachel T. Palmieri, MSPH1 Sarah J. Nyante, MSPH1 Daniel O. Koralek, MA, MS1,3 Sangmi Kim, PhD1 Patrick Bradshaw, MS1 Andrew F. Olshan, PhD1,3
The literature examining obesity as a barrier to screening for breast, cervical, and colorectal cancer has not been evaluated systematically. With the increasing prevalence of obesity and its impact on cancer incidence and mortality, it is important to determine whether obesity is a barrier to screening so that cancers among women at increased risk because of their body size can be detected early or prevented entirely. On the basis of 32 relevant published studies (10 breast cancer studies, 14 cervical cancer studies, and 8 colorectal cancer studies), the authors reviewed the literature regarding associations between obesity and
Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina.
recommended screening tests for these cancer sites among women in the U.S.
2
observed for cervical cancer. Most studies reported an inverse relation between
1
International Epidemiology Institute, Rockville, Maryland. 3
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina.
The most consistent associations between obesity and screening behavior were decreased cervical cancer screening and increasing body size, and several studies reported that the association was more consistent among white women than among black women. For breast cancer, obesity was associated with decreased screening behavior among white women but not among black women. The literature regarding obesity and colorectal cancer screening adherence was mixed, with some studies reporting an inverse effect of body size on screening behavior and others reporting no effect. Overall, the results indicated that obesity most likely is a barrier to screening for breast and cervical cancers, particularly among white women; the evidence for colorectal cancer screening was inconclusive. Thus, efforts to identify barriers and increase screening for breast and cervical cancers may be targeted toward obese women, whereas outreach to all women should remain the objective for colorectal cancer screening programs. Cancer 2008;112:1892–904. 2008 American Cancer Society.
KEYWORDS: obesity, body mass index, mammogram, Papanicolaou smear, colonoscopy, sigmoidoscopy, occult blood, literature review.
Supported in part by grants from the National Cancer Institute (T32 CA009330-26, T32 CA72319-10, and R25 CA57726). We thank Dr. Etta D. Pisano and Dr. Robert S. Sandler for helpful discussion during the writing of this article. Address for reprints: Sarah S. Cohen, MS, Department of Epidemiology, School of Public Health, CB 7435, University of North Carolina, Chapel Hill, NC 27599; Fax: (301) 424-1054; E-mail: sarahcohen@ unc.edu Received August 27, 2007; revision received October 15, 2007; accepted November 20, 2007.
ª 2008 American Cancer Society
T
he objective of a cancer screening program is to detect cancerous and precancerous lesions in asymptomatic individuals, which, with effective treatment, will decrease cancer-related morbidity and mortality. In the U.S., screening programs exist for cancers of the breast, cervix, and colon and rectum, which will account for an estimated 326,290 new cancer cases and 69,850 cancer deaths in 2007 among women in the U.S.1 For breast cancer, the U.S. Preventive Services Task Force (USPSTF) and the American Cancer Society (ACS) both recommend screening mammography for women aged 40 years who are at average risk of breast cancer, either annually (ACS) or every 1 to 2 years (USPSTF).2,3 For cervical cancer, the ACS recommends Papanicolaou (Pap) tests every 1 or 2 years beginning 3 years after the onset of sexual activity or age 21 years, whichever comes first. After age 30 years, the screening interval may be relaxed to 2 or 3 years
DOI 10.1002/cncr.23408 Published online 24 March 2008 in Wiley InterScience (www.interscience.wiley.com).
Obesity and Cancer Screening: A Review/Cohen et al.
based on previous Pap test results and other risk factors.4 The USPSTF recommends that screening end at age 65 years, whereas the ACS recommends ceasing at age 70 years, and both the ACS and the USPSTF recommend that women who have had a total hysterectomy for a benign condition not be screened for cervical cancer.5–7 For colorectal cancer, the ACS recommends either colonoscopy every 10 years, sigmoidoscopy every 5 years, or yearly fecal occult blood test (FOBT), beginning at age 50 years.4,8 The USPSTF has not established evidence that colonoscopy is effective in reducing mortality from colorectal cancer and, thus, recommends screening women aged 50 years with FOBT, sigmoidoscopy, or both.9 National screening rates for breast and cervical cancer are relatively high. On the basis of 2004 Behavioral Risk Factor Surveillance System (BRFSS) data, 74.9% of women aged >40 years received a mammogram within the past 2 years, and 86% of women aged >18 years received a Pap test within the past 3 years.10 In contrast, colorectal cancer screening rates are much lower. According to data from the 2003 National Health Interview Survey (NHIS), only 33% of adults reported receiving endoscopy (ie, sigmoidoscopy or colonoscopy) in the previous 5 years, and 15% reported an FOBT in the previous year.11 The percentage of American women who are overweight or obese has been increasing steadily in recent decades.12,13 Between 1976 and 2004, the percentage of overweight women (ie, body mass index [BMI] 25, calculated as weight in kilograms divided by the square of height in meters [kg/m2]) rose markedly, from 38.7% to 57.1% in white women and from 62.6% to 79.5% in black women.13 According to National Health and Nutrition Examination Survey data for 2000 through 2004, 31.5% of white women and 51.6% of black women were obese (BMI 30 kg/ m2).13 The rapid increase in the prevalence of obesity, coupled with the suggestion that 20% of cancer deaths among women in the U.S. in 2000 were attributable to obesity14 and the evidence indicating that obesity is a modifiable risk factor for both postmenopausal breast cancer and colorectal cancer,15 highlights the importance of cancer screening among overweight and obese women. To our knowledge, the literature on obesity as a barrier to cancer screening among women has not been evaluated systematically. The purpose of this review was to evaluate the evidence regarding the effect of obesity on the receipt of recommended screening tests for breast, cervical, and colorectal cancer among women in the
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U.S. With the increasing prevalence of obesity and its impact on cancer incidence and mortality, it is imperative to determine whether obesity is a barrier to screening so that cancers among women who already are at increased risk can be detected as early as possible or prevented altogether.
MATERIALS AND METHODS We conducted a PubMed search between January and February 2007 for each of 3 cancer sites (breast, cervical, and colorectal). We used a standard set of terms for body size for all 3 searches that included the following terms: obesity, body mass index, BMI, obese, overweight, body weight, and body size. For breast cancer, the screening search terms included breast cancer screening, mammography, and mammogram. For the cervical cancer search, we used the terms cervical cancer screening, Papanicolaou test, Pap test, Pap smear, pelvic examination, and gynecologic examination. The colorectal cancer search terms included colorectal cancer screening; colonoscopy; sigmoidoscopy; and fecal occult blood test. We limited our search to articles written in English. For our search of references related to colorectal cancer screening, we included articles that reported study results for women only or stated that sex-stratified results were equivalent. We screened references from each search first on the basis of title and abstract and then by reviewing the full article. Articles that were considered relevant were those with any data that either estimated the prevalence of screening behaviors or characteristics by body size or that estimated the relative risk or relative prevalence of screening by body size. Two investigators independently reviewed all of the references and abstracted the selected articles; discrepancies were resolved by consensus. Our search related to mammography initially produced 743 articles. After review, we identified 16 articles that specifically addressed the relation between screening mammography and obesity. Of those 16 articles, 7 were excluded because they dealt with populations outside of the U.S. This exclusion criterion was used because healthcare systems and access to cancer screening services vary widely between countries. The cited references of the remaining 9 articles suggested 1 additional reference, yielding a total of 10 articles for this review (Table 1).16–25 Our search of cervical cancer screening and obesity yielded 192 references. We identified 11 relevant articles on cervical cancer screening and body size. Three additional articles were identified from the cited references, for a total of 14 studies to be
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included in this review (Table 2).16,19–23,26–32 Our initial search of colorectal cancer screening and obesity resulted in 275 references. After review, 6 articles were identified for inclusion. The cited references from the initial articles identified 2 additional studies, resulting in 8 studies for inclusion in this review (Table 3).33–40
RESULTS Obesity Classifications Obesity was measured most frequently by BMI, which was usually grouped according to standard cutoff points defined by the World Health Organization (WHO) as underweight (BMI 130% of their ideal body weight were considered obese)29 and the Ponderal Index (calculated as height in inches/cube root of weight in pounds).31
Breast Cancer Screening Outcome definitions ‘Recent mammography’ (also referred to as ‘compliance with breast cancer screening’) was defined most often as having had at least 1 mammogram within the past 2 years,16,17,19,21–25 although a mammogram within the past 3 years was used in 1 study.20 Age at first mammogram was examined in 1 study.18 Study designs The majority of the mammography studies were cross-sectional and included data from single hospitals,18 regional mammography networks, health plans, and convenience samples16,17,19 and from national population surveys, including the BRFSS,21 the NHIS,20,23–25 and the Health and Retirement Study (HRS).22 In most studies, mammography information, height, and weight were obtained from selfreport; a few studies obtained these data through
medical chart abstraction.17–19 In general, women aged >40 years16,19,21,25 or aged >50 years17,22–24 were included in the analyses.
Study findings Three studies examined the relation between increasing categories of BMI and failure to have a recent mammogram separately among white women and black women.22,24,25 Among white women, these studies consistently demonstrated that women in the highest BMI categories were less likely to have had a recent mammogram than healthy weight women with odds ratios (ORs) for the most extreme body size categories ranging from 0.59 to 0.90.22,24,25 The results were less consistent among black women, with either no association22 or associations in the opposite direction of those observed among white women.24,25 In studies that did not stratify by race, the observed associations between recent mammography and obesity were less clear. Two unstratified studies demonstrated a positive association between increasing BMI category and an increased likelihood of not having had a recent mammogram.21,23 However, in 2 other unstratified studies, the authors reported no significant association between BMI and recent mammography,19,20 although the trend was suggestive in the report by Fontaine et al.20 In the few studies that examined underweight women (BMI 55 kg/m2 (68%).16 Carney et al. reported that women who adhered to a 2-year screening protocol had a lower mean BMI compared with women who did not adhere to screening recommendations,17 and Colbert et al. reported that women with a larger body size were older when they initiated mammography use.18
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TABLE 1 Association Between Obesity and Mammography Screening Behavior for Breast Cancer Cross-sectional study Fontaine 199820 Location and date Population characteristics Analysis sample size
Study description
US, 1992 Aged 18 y; US residents who self-reported sociodemographic information and use of healthcare services; 80% white 3105
Wee 200023 Location and date Population characteristics Analysis sample size
US, 1994 Ages 50–75 y; 81% white 3502
Fontaine 200121 Location and date Population characteristics Analysis sample size
US, 1998 Aged 40 y; 84% white 38,682
Carney 200217 Location and date Population characteristics Analysis sample size Wee 200424 Location and date Population characteristics Analysis sample size
NH, US, 1996 Aged 50 y; race NR 625 US, 1998 Ages 50–75 y; 74% white 5277
Colbert 200418 Location and date Population characteristics Analysis sample size
US, 2000–2002 Women receiving first mammogram; excluded women on Medicare; 90% white 786
Ostbye 200522 Location and date Population characteristics Analysis sample size
US, 1995, 1996, 2000 HRS: ages 51–61 y, 82% white; AHEAD: ages 70 y, 86% white HRS, 4439; AHEAD, 4010
Results Mammogram within past 3 y BMI, kg/m2* OR [95% CI] 25.1 1.00 35 40
0.81 [0.59–1.12] 0.73 [0.45–1.19] Mammogram within past 2 y BMI, kg/m2 RD [95% CI] 18.5–24.9 0 25–29.9 22.8[26.7–0.9] 30–34.9 25.3 [211.1–0.5] 35–39.9 24.5 [212.5–3.4] 40 28.8 [222.9–5.3] Mammogram within past 2 y OR [95% CI] BMI, kg/m2 55 67.7% No mammogram in past 2 y: White women only BMI, kg/m2 OR [95% CI]
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