|
 |
|
|||||||
|
|||||||||
© 2005 American Public Health Association
DOI: 10.2105/AJPH.2003.032656
RESEARCH AND PRACTICE |
At the time the study was completed, Susan E. Jelinski was with the Department of Community Health Sciences, University of Calgary, Alberta. Colleen J. Maxwell was with the departments of Community Health Sciences and Medicine, University of Calgary, and a fellow with the Institute of Health Economics, Edmonton, Alberta. Jay Onysko and Christina M. Bancej were with the Chronic Disease Prevention Division, Health Canada, Ottawa, Ontario.
Correspondence: Requests for reprints should be sent to Colleen J. Maxwell, PhD, Department of Community Health Sciences, Faculty of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta, Canada T2N 4N1 (e-mail: maxwell{at}ucalgary.ca).
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
|---|
Objectives. We evaluated whether breast self-examination (BSE) influences subsequent mammography participation.
Methods. We evaluated associations between BSE and subsequent mammography participation, adjusting for baseline screening behaviors and sociodemographic, health, and lifestyle characteristics, among women aged 40 years and older using data from the longitudinal Canadian National Population Health Survey.
Results. Regular performance of BSE at baseline was not associated with receipt of a recent mammogram at follow-up among all women (adjusted odds ratio [OR]=1.01; 95% confidence interval [CI]= 0.75, 1.35) or with mammography uptake among the subgroup of women reporting never use at baseline (adjusted OR=0.78; 95% CI=0.50, 1.22).
Conclusions. The lack of association between performance of BSE and subsequent mammography participation suggests that not recommending BSE is unlikely to influence mammography participation.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
|---|
In North America, breast cancer is the most frequently diagnosed cancer in women and a leading cause of premature death.1,2 The current methods employed to screen for or detect breast cancer include mammography, clinical breast examination (CBE), and breast self-examination (BSE). The effectiveness of routine mammography screening in the reduction of breast cancer mortality in women aged 50 to 69 years has been demonstrated.3–12 Authors of a review on the effectiveness of CBE have concluded that CBE should be conducted in women aged 40 and older as it may contribute to breast cancer mortality rate reduction.13 However, the effectiveness of BSE in preventing death from breast cancer has been challenged of late.14
Two recent systematic reviews of routine teaching or performing of BSE to screen for breast cancer among women aged 40 and older question the balance of benefits and harms of these practices.15,16 The Canadian Task Force on Preventive Health Care concluded there was insufficient evidence to continue promotion of the routine teaching of BSE during periodic health examinations of women, and further concluded that there is fair evidence of harm from BSE owing to unnecessary diagnostic procedures.15 The task force cited Russian and UK studies in which the number of physician visits and the rate of benign breast biopsies were higher among the study participants in the BSE performance groups as compared to control groups.17,18 The US Preventive Services Task Force (USPSTF) questioned the generalizability of these trials to US women, concluding that the evidence is insufficient to recommend for or against teaching or performing routine BSE.16 The group further cited concerns that other potential adverse outcomes of discontinuing BSE, including influence on subsequent screening behaviors, have not been evaluated.
As a result, considerable debate has erupted about the potential negative effects of discontinuing the routine promotion and teaching of BSE.19–24 It is possible, for example, that performance of regular BSE may inculcate the importance of breast health among women. If so, then one possible negative consequence of the recent recommendations to discontinue routine teaching of BSE would be that the perceived lack of support for BSE could lead to more widespread negative attitudes and behaviors among women in terms of other recommended breast cancer screening strategies, namely routine CBE and participation in mammography screening.
Our objective with this prospective study was to elucidate potential relationships between various breast health behaviors. Based on longitudinal panel data for a representative cohort of Canadian women aged 40 and older assessed in the 1996–1997 and 1998–1999 cycles of the National Population Health Survey (NPHS), we specifically addressed the following 2 research questions: (1) the relative importance of BSE to subsequent participation in mammography screening among all women, and (2) the significance of BSE as an independent predictor of mammography uptake among women who had never used mammography at baseline.
|
METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
|---|
Respondents
In this investigation we included women who participated in both the 1996–1997 and 1998–1999 cycles of the NPHS and who were aged 40 or older at the time of the first survey (baseline). The NPHS is a split-panel survey that combines repeated cross-sectional components with longitudinal follow-up in a panel of respondents. Participants undergo a personal interview by telephone in which data regarding various health and health care indices as well as demographic and socioeconomic characteristics are collected. The participants constitute a representative group of Canadian household residents aged 12 years and older from all 10 provinces and are sampled using a multistage probability design with stratification and clustering at various stages. Data from the 1994–1995 NPHS (the first survey cycle) were not examined, as items pertaining to BSE practices were not included in the survey questionnaire. Details of the sampling procedures, design, and response rates are available elsewhere.25,26
The initial sample included 3952 women. Of these, 384 women did not respond to the question on mammogram use in either the 1996–1997 or 1998–1999 survey and were removed from the sample. Another 3 women were excluded because they failed to indicate the approximate date of their most recent mammogram. Other exclusions included 20 women with missing data regarding CBE or BSE participation (including ever use, approximate timing, and frequency). This resulted in a final sample of 3545 for the present analyses.
Measures
Women were defined as having a recent mammogram in 1998–1999 if they reported having a mammogram within 2 years of completing the survey. New users of mammography ("uptakers") were those reporting never use at baseline (1996–1997) but recent mammogram participation at follow-up (1998–1999). To account for inconsistent responses in mammography participation between the 1996–1997 and 1998–1999 surveys, the following corrections were made: (1) if a woman reported having a mammogram more than 2 years prior to the 1998–1999 survey, yet reported never having a mammogram in the 1996–1997 survey (n = 72), she was considered to have had a recent mammogram in 1998–1999; and (2) women who reported having had a mammogram in 1996–1997 yet reported never having had one in 1998–1999 (n = 38) were considered to be never users at baseline (1996–1997). These corrections were based on findings from mammography self-report validation studies27–31 and the characteristics of the different types of inconsistent respondents in the NPHS.
Performance of BSE was coded as regular (a BSE at least once every 3 months), infrequent (less than once every 3 months), or no (for women reporting never having performed BSE).
We examined sociodemographic, health, and lifestyle factors previously associated with mammography use32–41 as well as other screening behaviors as potential confounding factors. Sociodemographic data included age, urban/rural residence, household income, education, language, marital status, and volunteer group participation. Respondents who reported being a member of any voluntary organizations or associations (including school groups, church, ethnic or other social groups), community centers, or both, were coded as participating in a voluntary group. Health and lifestyle variables included having a regular doctor, number of medical consultations in the past year, frequency of physical activity, smoking status, and use of hormone replacement therapy. Other baseline screening practices included blood pressure check, Papanicolaou test, mammography, and CBE. For all screening practices, a recent screen was defined as having occurred within 2 years of the baseline survey whereas a prior screen was defined as having occurred 2 or more years previous.
Statistical Analysis
Two multivariable logistic regression analyses42 were performed to determine the predictive value of breast screening behaviors in 1996–1997 for mammography participation in 1998–1999, adjusting for relevant confounding factors. The first model included all women in the sample (n = 3545) to examine the relative importance of all baseline BSE behaviors in predicting a recent mammogram in 1998–1999. The second model included only those women who reported never having had a mammogram in 1996–1997 (n = 1231) to examine the significance of BSE as an independent predictor of mammography uptake (i.e., recent use in 1998–1999).
All breast health behaviors and potential confounders were first examined using age-adjusted bivariable analyses. Factors independently associated with the outcome in question were assessed as possible confounders by incorporating each covariate into a multiple logistic model containing the baseline screening behaviors modeled against the mammography participation outcome in question. If the influence of a potential confounder created a 10% or greater change in the odds ratio (OR) for any baseline screening behavior, it was included in the final model regardless of significance in order to obtain an unbiased estimate of the effect of baseline screening behavior on future mammography participation.43 Factors that did not confound the association between baseline screening behavior and future mammography participation, but that were independently associated with future mammography participation, were retained in the final model on the basis of statistical significance (P
0.05).
To account for stratification and clustering in the NPHS sampling design, exact standard errors for ORs were calculated using bootstrap resampling methods allowing 95% confidence intervals (CIs) to be calculated. For both logistic regression models, cases with missing information for the predictor variables were collapsed into the reference categories. With the exception of income, all examined predictor variables had 1% of cases or less with missing values (7.3% and 7.8% for income in the first and second models, respectively). Additional sensitivity analyses were performed (e.g., excluding women with inconsistent responses, recoding BSE frequency to define "regular BSE" as monthly) to permit further investigation of our selected coding strategy.
All analyses were weighted to reflect the 1994–1995 Canadian population (which corresponds to the first cycle of the NPHS) in terms of age group and gender.26 The statistical analyses were performed using SAS 8.02 for Windows (SAS Institute Inc, Cary, NC).
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
|---|
Breast Screening Practices as Predictors of a Subsequent Mammogram
Among the total sample, approximately 61% reported regular performance of BSE and 67% reported receiving a recent CBE at baseline (Table 1
). An equal proportion of women (20%) reported never having performed a BSE or having received a CBE at baseline.
|
In age-adjusted bivariable analyses, women reporting a recent CBE or regular performance of BSE were significantly more likely to receive a recent mammogram at follow-up (OR = 2.60; 95% CI = 2.03, 3.32 and OR = 1.31; 95% CI = 1.05, 1.64, respectively) (Table 1
). However, both practices failed to remain statistically significant predictors of subsequent mammography use after adjustment for relevant confounding factors (OR = 1.24; 95% CI = 0.92, 1.66 and OR = 1.01; 95% CI = 0.75, 1.35; respectively). Among performers of BSE, we also found that those who were taught BSE by a physician or nurse were more likely to participate in mammography screening at follow-up (data not shown). However, the provision of BSE instruction by a health professional did not remain statisically significant in our multivariable model. Other than age group, the strongest predictor of subsequent mammography use was recent or prior mammography participation at baseline. Other significant baseline predictors included being aged 50 to 59 years, reports of a recent Papanicolaou test, higher number of consultations with a physician in the past year, and being a nonsmoker.
Breast Screening Practices as Predictors of Mammography Uptake
Among the subsample of women who reported never having had a mammogram at baseline, approximately 55% reported regular performance of BSE and 50% reported receiving a recent CBE in 1996–1997 (Table 2). Approximately 26% reported never having performed BSE and 31% reported never having received a CBE at baseline.
|
A recent CBE was found to be a significant predictor of mammography uptake even after adjustment for potential confounding factors (age-adjusted OR = 1.80; 95% CI = 1.18, 2.75 and adjusted OR = 1.60; 95% CI = 1.00, 2.57) (Table 2
). Although not statistically significant, regular performance of BSE at baseline showed a negative association with mammography uptake during follow-up (age-adjusted OR = 0.85; 95% CI = 0.55, 1.29 and adjusted OR = 0.78; 95% CI = 0.50, 1.22). Other significant baseline predictors of mammography uptake included reports of a recent Papanicolaou test, no participation in a voluntary group, and being within the age range (50–69 years) targeted by selected Canadian organized screening programs for mammography use. The incorporation of alternative coding strategies for inconsistent respondents (i.e., excluding women with inconsistent responses for mammography participation between the 1996–1997 and 1998–1999 cycles) and for defining regular BSE on a monthly basis rather than at least once every 3 months did not significantly alter the findings from the multivariable logistic models.
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
|---|
There has been much debate recently about the role of BSE as an effective screening practice to reduce the risk of death from breast cancer. Authors of a recent study have concluded that BSE did not reduce breast cancer mortality in a sample of approximately 266000 Chinese women.14 Further, a Canadian publication has recommended the cessation of routine teaching of BSE.15 The reasons cited include lack of evidence for the efficacy of BSE in reducing breast cancer mortality as well as potential increases in adverse outcomes associated with BSE practices attributable to increased incidence of benign breast biopsies, increases in the number of physician visits and costs, and patient anxiety.15 The USPSTF was more conservative, but still concluded that the evidence is insufficient to recommend for or against teaching or performing routine BSE.16
It is possible that participation in any 1 of the 3 breast screening strategies (BSE, CBE, mammography) may influence the practice of the other 2 strategies, and that women who perform BSE may be more likely to participate in other recommended screening behaviors. A resulting concern, therefore, is that the relative lack of support for BSE may reduce participation in breast health strategies overall, including mammography. However, our present analyses based on Canadian women aged 40 and older participating in the longitudinal panel of the NPHS suggest that BSE is not an independent predictor of mammography participation. This finding was consistent when breast screening strategies were evaluated for all women in the sample, as well as for the subgroup of women who potentially could have been new users of mammography in 1998–1999.
Conversely, women who reported recent use of other positive screening practices at baseline (e.g., mammogram, Papanicolaou test) were significantly more likely to report a recent mammogram in 1998–1999. This is not unexpected, given findings from previous studies demonstrating the significance of previous screening behaviors (especially mammography use) as independent predictors of subsequent participation in mammography screening at recommended intervals.39,44
Participation in CBE at baseline influenced mammography uptake during the 2-year interim between surveys. Previous studies have similarly reported a positive relationship between CBE and mammography participation.45,46 This finding highlights the importance of regular physician contact and the relevance of physicians’ recommendations47,48 regarding recommended screening behaviors, particularly among previously never-screened women. Many organized breast screening programs in various Canadian provinces and in the United States also provide CBE during a routine screening examination.49,50 It is important to note that, in our study, performance of CBE increased subsequent mammography participation. Although a recent study found only a small relative contribution of CBE to early detection in programs delivering both mammography and CBE, program policies concerning the delivery of screening by CBE should also consider the reinforcing effect of CBE performance on mammography uptake.51
The observed inverse association between being a member of a voluntary group and mammography uptake by the 2-year follow-up was unexpected, given previous cross-sectional findings of a positive association between voluntary group membership and ever having had a mammogram among women aged 50 to 69 years.41 One possible explanation for this discrepancy relates to the different age groups and mammography outcomes examined in the current study. For example, younger women (aged 40–49 years) may be more likely to be members of voluntary groups but less likely to be uptakers of mammography screens, particularly in Canada, where mammography use is only actively promoted among women aged 50 to 69 years.
The limitations of this study include those routinely associated with self-reported survey data. For mammography in particular, however, previous studies have demonstrated a high level of agreement between self-reports of mammography and confirmed mammography records.27,31,52 Our analyses were also limited to those women who responded to the NPHS. However, the design features of the NPHS, which had a response rate of 98.5% in 1998–1999, suggest that our estimates are unlikely to have been influenced by nonresponse bias.
In conclusion, the absence of a significant association between performance of BSE and subsequent mammography participation observed in the present study suggests that the current recommendations regarding BSE are unlikely to have an adverse effect on recommended breast cancer screening practices. Previous mammography screening behaviors and participation in time-appropriate cancer screening strategies (including CBE and Papanicolaou tests) continue to represent significant determinants of future mammography behaviors. However, our findings do not exclude the possibility that the promotion and teaching of BSE may indeed function to enhance women’s awareness of breast health. Our research also does not directly address the impact of discontinuing the promotion and teaching of BSE. Further research is required to identify specific strategies that both empower women and promote screening behaviors with proven health benefits.
|
Acknowledgments |
|---|
This research was supported by the Cancer Division, Health Canada (grant ISC3164). S.E. Jelinski’s postdoctoral fellowship was funded by The Merck Company Foundation, the philanthropic arm of Merck and Company, Whitehouse Station, NJ (grant to the Institute of Health Economics, Edmonton, Alberta). C.J. Maxwell is funded by a New Investigator Award (grant SIC 55775) from the Institute of Aging, Canadian Institutes of Health Research, and a Population Health Investigator Award from the Alberta Heritage Foundation for Medical Research.
Human Participant Protection
The NPHS is an ongoing survey conducted by Statistics Canada. As such, data are collected in accordance with Canada’s Statistics Act, which governs the protection of privacy of survey subjects.
|
Footnotes |
|---|
Peer Reviewed
Contributors
S. E. Jelinski and C. J. Maxwell contributed to the initial and revised analyses of the NPHS panel data, the interpretation of the results, and the initial drafting and editing of the article. J. Onysko and C. M. Bancej were responsible for the data linkage with Statistics Canada (for the NPHS share file) and for the revised bootstrap analyses, and also contributed to the interpretation of the results and editing of the article.
Accepted for publication March 17, 2004.
|
References |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
|---|
1. National Cancer Institute of Canada. Canadian Cancer Statistics 2003. Toronto: National Cancer Institute of Canada; 2003.
2. American Cancer Society. Cancer Statistics Slide Set 2003. Atlanta, Ga: American Cancer Society. Available at: http://www.cancer.org/docroot/STT/stt_0.asp. Accessed December 7, 2004.
3. Verbeek AL, Hendriks JH, Holland R, Mravunac M, Sturmans F, Day NE. Reduction of breast cancer mortality through mass screening with modern mammography. First results of the Nijmegen project, 1975–1981. Lancet. 1984;1:1222–1224.[Web of Science][Medline]
4. Tabar L, Fagerberg CJ, Gad A, et al. Reduction in mortality from breast cancer after mass screening with mammography. Randomised trial from the Breast Cancer Screening Working Group of the Swedish National Board of Health and Welfare. Lancet. 1985;1: 829–832.[Medline]
5. Andersson I, Aspegren K, Janzon L, et al. Mammographic screening and mortality from breast cancer: the Malmo mammographic screening trial. BMJ. 1988; 297:943–948.
6. Roberts MM, Alexander FE, Anderson TJ, et al. Edinburgh trial of screening for breast cancer: mortality at seven years. Lancet. 1990;335:241–246.[CrossRef][Web of Science][Medline]
7. Miller AB, Baines CJ, To T, Wall C. Canadian National Breast Screening Study: 1. Breast cancer detection and death rates among women aged 40 to 49 years. CMAJ. 1992;147:1459–1476.[Abstract]
8. Miller AB, Baines CJ, To T, Wall C. Canadian National Breast Screening Study: 2. Breast cancer detection and death rates among women aged 50 to 59 years. CMAJ. 1992;147:1477–1488.[Abstract]
9. de Koning HJ, Boer R, Warmerdam PG, Beemsterboer PM, van der Maas PJ. Quantitative interpretation of age-specific mortality reductions from the Swedish breast cancer-screening trials. J Natl Cancer Inst. 1995;87:1217–1223.
10. Kerlikowske K, Grady D, Rubin SM, Sandrock C, Ernster VL. Efficacy of screening mammography. A meta-analysis. JAMA. 1995;273:149–154.
11. Alexander FE, Anderson TJ, Brown HK, et al. 14 years of follow-up from the Edinburgh randomised trial of breast-cancer screening. Lancet. 1999;353: 1903–1908.[CrossRef][Web of Science][Medline]
12. International Agency for Research on Cancer. Breast Cancer Screening. Lyon, France: IARC Press; 2002. International Agency for Research on Cancer. IARC Handbooks of Cancer Prevention; vol 7.
13. Barton MB, Harris R, Fletcher SW. The rational clinical examination. Does this patient have breast cancer? The screening clinical breast examination: should it be done? How? JAMA. 1999;282: 1270–1280.
14. Thomas DB, Gao DL, Ray RM, et al. Randomized trial of breast self-examination in Shanghai: final results. J Natl Cancer Inst. 2002;94:1445–1457.
15. Baxter N. Preventive health care, 2001 update: should women be routinely taught breast self-examination to screen for breast cancer? CMAJ. 2001;164: 1837–1846.
16. Humphrey LL, Helfand M, Chan BK, Woolf SH. Breast cancer screening: a summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med. 2002;137(5 pt 1):347–360.
17. Semiglazov VF, Moiseyenko VM, Bavli JL, et al. The role of breast self-examination in early breast cancer detection (results of the 5-years USSR/WHO randomized study in Leningrad). Eur J Epidemiol. 1992;8: 498–502.[CrossRef][Web of Science][Medline]
18. Ellman R, Moss SM, Coleman D, Chamberlain J. Breast self-examination programmes in the trial of early detection of breast cancer: ten year findings. Br J Cancer. 1993;68:208–212.[Web of Science][Medline]
19. Miller AB, Baines C, Harvey B. Breast self-examination [letter]. CMAJ. 2002;166:163; discussion 166, 168.
20. Warner E. Breast self-examination [letter]. CMAJ. 2002;166:163; discussion 166, 168.
21. Clifford TJ, Sampson M, Schachter HM. Breast self-examination [letter]. CMAJ. 2002;166:164; discussion 166, 168.
22. Mahoney L. Breast self-examination [letter]. CMAJ. 2002;166:164; discussion 166, 168.
23. Winters L. Breast self-examination [letter]. CMAJ. 2002;166:164–165; discussion 166, 168.
24. Snell S. Breast self-examination [letter]. CMAJ. 2002;166:165; discussion 166, 168.
25. Tambay JL, Catlin G. Sample design of the National Population Health Survey. Health Rep. 1995;7: 29–38 [in English]; 31–42 [in French].[Medline]
26. Swain L, Catlin G, Beaudet MP. The National Population Health Survey—its longitudinal nature. Health Rep. 1999;10:69–82 [in English]; 73–89 [in French].[Medline]
27. King ES, Rimer BK, Trock B, Balshem A, Engstrom P. How valid are mammography self-reports? Am J Public Health. 1990;80:1386–1388.
28. Degnan D, Harris R, Ranney J, Quade D, Earp JA, Gonzalez J. Measuring the use of mammography: two methods compared. Am J Public Health. 1992;82: 1386–1388.
29. Fulton-Kehoe D, Burg MA, Lane DS. Are self-reported dates of mammograms accurate? Public Health Rev. 1992;20:233–240.[Medline]
30. Gordon NP, Hiatt RA, Lampert DI. Concordance of self-reported data and medical record audit for six cancer screening procedures. J Natl Cancer Inst. 1993; 85:566–570.
31. Zapka JG, Bigelow C, Hurley T, et al. Mammography use among sociodemographically diverse women: the accuracy of self-report. Am J Public Health. 1996; 86:1016–1021.
32. Zapka JG, Stoddard A, Maul L, Costanza ME. Interval adherence to mammography screening guidelines. Med Care. 1991;29:697–707.[Web of Science][Medline]
33. Miller AM, Champion VL. Mammography in women > or = 50 years of age. Predisposing and enabling characteristics. Cancer Nurs. 1993;16:260–269.[Web of Science][Medline]
34. Hitchcock JL, Steckevicz MJ, Thompson WD. Screening mammography: factors associated with adherence to recommended age/frequency guidelines. Womens Health. 1995;1(3):221–235.[Medline]
35. Lee JR, Vogel VG. Who uses screening mammography regularly? Cancer Epidemiol Biomarkers Prev. 1995;4:901–906.[Abstract]
36. McCarthy BD, Yood MU, MacWilliam CH, Lee MJ. Screening mammography use: the importance of a population perspective. Am J Prev Med. 1996;12:91–95.
37. Phillips KA, Kerlikowske K, Baker LC, Chang SW, Brown ML. Factors associated with women’s adherence to mammography screening guidelines. Health Serv Res. 1998;33:29–53.[Web of Science][Medline]
38. May DS, Kiefe CI, Funkhouser E, Fouad MN. Compliance with mammography guidelines: physician recommendation and patient adherence. Prev Med. 1999;28:386–394.[CrossRef][Web of Science][Medline]
39. Parker JD, Sabogal F, Gebretsadik T. Relationship between earlier and later mammography screening—California Medicare, 1992 through 1994. West J Med. 1999;170:25–27.[Web of Science][Medline]
40. Segura JM, Castells X, Casamitjana M, Macia F, Ferrer F. Utilization of screening mammography as a preventive practice prior to initiating a population-based breast cancer screening program. J Clin Epidemiol. 2000;53:595–603.[CrossRef][Web of Science][Medline]
41. Maxwell CJ, Bancej CM, Snider J. Predictors of mammography use among Canadian women aged 50–69: findings from the 1996/97 National Population Health Survey. CMAJ. 2001;164:329–334.
42. Kelsey JL, Whittemore AS, Evans AS, Thompson WD. Methods in Observational Epidemiology. 2nd ed. New York, NY: Oxford University Press; 1996.
43. Kleinbaum DG, Kupper LL, Muller KE, Nizam A. Applied Regression Analysis and Other Multivariable Methods. 3rd ed. Pacific Grove, Calif: Duxbury Press; 1998.
44. Liu X, Sennett C, Legorreta AP. Mammography utilization among California women age 40–49 in a managed care environment. Breast Cancer Res Treat. 2001;67:181–186.[CrossRef][Web of Science][Medline]
45. Solomon LJ, Mickey RM, Rairikar CJ, Worden JK, Flynn BS. Three-year prospective adherence to three breast cancer screening modalities. Prev Med. 1998;27: 781–786.[CrossRef][Web of Science][Medline]
46. Cummings DM, Whetstone L, Shende A, Weismiller D. Predictors of screening mammography: implications for office practice. Arch Fam Med. 2000;9: 870–875.
47. Fox SA, Murata PJ, Stein JA. The impact of physician compliance on screening mammography for older women. Arch Intern Med. 1991;151:50–56.
48. Grady KE, Lemkau JP, McVay JM, Reisine ST. The importance of physician encouragement in breast cancer screening of older women. Prev Med. 1992;21: 766–780.[CrossRef][Web of Science][Medline]
49. Bobo JK, Lee NC, Thames SF. Findings from 752,081 clinical breast examinations reported to a national screening program from 1995 through 1998. J Natl Cancer Inst. 2000;92:971–976.
50. Health Canada. Organized Breast Screening Programs in Canada: 1999 and 2000 Report. Ottawa: Minister of Public Works and Government Services Canada; 2001.
51. Bancej C, Decker K, Chiarelli A, Harrison M, Turner D, Brisson J. Contribution of clinical breast examination to mammography screening in the early detection of breast cancer. J Med Screening. 2003;10: 16–21.
52. Etzi S, Lane DS, Grimson R. The use of mammography vans by low-income women: the accuracy of self-reports. Am J Public Health. 1994;84:107–109.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |