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1 UCLA Multicampus Program in Geriatric Medicine and Gerontology, University of
California, 10945 Le Conte Ave., Ste. 2339, Los Angeles, CA 90095-1687.
2 Iris Cantor Center for Breast Imaging, University of California, Los Angeles,
CA 90095.
3 Rand Corporation, Santa Monica, CA 90401.
4 School of Public Health, University of California, Los Angeles, CA
90095.
Received April 8, 2002;
accepted after revision May 15, 2002.
Supported by the State of California Breast Cancer Research Program grant
4EB-6100.
Abstract
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SUBJECTS AND METHODS. We recruited a consecutive volunteer sample of 499 women ranging in age from 60 to 84 years who had not undergone mammography in the previous year to participate in a cluster randomized clinical trial about the benefit of on-site mobile mammography. Subjects were recruited from 60 community-based sites where seniors gather. The intervention included a structured on-site multicomponent educational program with or without available on-site mobile mammography. The primary outcome measure was self-reported receipt of mammography within 3 months of the intervention.
RESULTS. Women in the group offered access to on-site mammography and health education were significantly more likely than those in the group offered health education only to undergo mammography within 3 months (55% vs 40%, p = 0.001; adjusted [for clustering] odds ratio, 1.83; 95% confidence interval, 1.22-2.74). Gains from offering on-site mammography were shown for several ethnic and sociodemographic subgroups and were especially large for Asian American women.
CONCLUSION. Offering on-site mammography at community-based sites where older women gather is an effective method for increasing breast cancer screening rates among older women and may be particularly effective for some subgroups of women who traditionally have had low screening rates.
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The effectiveness of mammography in detecting early-stage breast cancer has been less well studied in older women, and recommendations are less precise for women in this age group. Nevertheless, several studies support the effectiveness of mammography in older women [2, 3], and two decision analyses support the use of breast cancer screening among older women. The first study evaluated screening until the age of 85 years and concluded that screening saves lives for all ages of older women [4]. The second study also supported mammography screening for women until the age of 79 years except among women in the lowest quartiles of bone mineral density; these women have a lower risk of breast cancer and are less likely to benefit from screening [5]. Moreover, the number of women who need to be screened to prevent one breast cancer—specific death among healthy 80-year-old women is similar to that for 50-year-old women [6]. Accordingly, the following major authorities recommend routine mammography screening without an upper age limit: American Cancer Society [7], American Geriatrics Society [8], American College of Radiology [9], American College of Preventive Medicine [10], and the United States Preventive Services Task Force [11].
Despite these guidelines, considerable evidence indicates that older women frequently do not undergo mammography. Based on 1997 Behavioral Risk Factor Surveillance System data, approximately 40% of the women in the United States who are 65 years old or older had not undergone mammography in the previous year [12]. Data from the 1998 National Health Interview Survey confirm the substantial gap between recommendations for mammography and rates of mammography use for older women. The rate of mammography use in the previous 2 years among all women 75 years old or older was only 57%, and that among women 65 years old or older who were below the poverty level was only 52% [13].
Attempts to increase the screening rate for breast cancer have included physician reminders and other office systems, physician audits with feedback, physician education, patient education, and community-based efforts [14,15,16,17,18,19,20]. Community-based interventions are appealing not only because they emphasize integrating preventive measures into daily life rather than "medicalizing" them, but also because they encourage women to take responsibility in maintaining their health.
Mobile mammography units have been used to overcome barriers of inaccessibility and the inconvenience of breast cancer screening. For a variety of reasons, mobile mammography may be more valuable for older women than for younger women. First, older women drive less frequently than older men, and female sex has also been an independent predictor of driving cessation after the age of 50 years [21]. Thus, transportation may be a more important factor among older than younger women. Second, older women frequently congregate at senior centers and meal sites, thereby providing a logical location for screening large numbers of women at a single site. Third, older women who see their peers participating in a mobile mammography program may be more inclined to participate. This influence may prevent women from citing age as a reason for not receiving mammography (i.e., "age attribution" or declining this test because of being "too old") [22].
Although mobile mammography has the potential of increasing breast cancer screening rates in older women, few data are available to support its effectiveness in this population. To date, only one randomized clinical trial about the use of on-site mobile mammography for older women has been reported [15]. In that study of women living in retirement communities, the rate of mammography use at 3 months was substantially higher among those who received health education and had access to mobile mammography than in the control group (45% vs 12%). However, the design of the study was unable to separate the effect of the on-site unit from the effect of health education.
In a prior case series, we found a high number of women underwent breast cancer screening when they had access to on-site mammography at urban meal sites and other sites where older persons congregate [22]. In this article, we report the results of a randomized clinical trial to test whether offering on-site mobile mammography combined with health education is more effective at increasing breast cancer screening rates than offering health education alone.
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Participants
The study recruited women who were 60-84 years old at study entry. The
upper age boundary was based on a decision analysis model that showed a steep
decline in marginal savings in life expectancy resulting from screening
mammography for women 85 years old or older
[4]. Moreover, this upper age
boundary was also consistent with the position statement (at the time of the
study's inception) of the American Geriatrics Society on breast cancer
screening [23].
Exclusionary criteria included recent mammography (within the past year), no telephone, inability to speak English or Spanish, and limited cognitive capacity to participate in the study (based on failure to be oriented to the date and day of the week and inability to place numbers appropriately on an outline of a clock) [24].
Interventions
The educational intervention used the framework of the Adherence Model, a
synthesis of some of the major social science theoretic formulations in the
area of adherence behavior
[16,
25]. Specifically, the health
education intervention consisted of a Senior Women's Health Day of educational
programs presented at sites where older persons gather. At the 16 sites where
a large number of Hispanic women gather, the entire Senior Women's Health Day
was presented in both English and Spanish.
During each health day, educational sessions focused on three activities, one of which was a lecture about breast cancer and mammography. The other activities were usually a lecture about stroke prevention and a participatory demonstration about the effect of exercise on arthritic joints. The total presentation time averaged between 30 and 60 min.
Key teaching points in the 10- to 20-min breast cancer and mammography lecture included the following: advancing age is the most important risk factor for breast cancer, the lifetime risk of breast cancer for all women is one in eight, symptoms are typically absent during the early stages of breast cancer, and options for treatment other than mastectomy are available if breast cancer is detected in the early stages. Using a necklace of beads, health education facilitators taught participants about the difference in size between lumps that can be detected clinically and mammographically [26].
At the end of the entire program, each participant was given a bag that included a set of beads like that used in the demonstration, health education pamphlets (developed by the National Cancer Institute, the American Cancer Society, and the Susan G. Komen Foundation), an educational videotape (developed by the American Cancer Society), and a directory of community-based sites where she could undergo mammography (developed by researchers at Rand [Santa Monica, CA]). Within 2 weeks of the health day program, each participant received a letter that reminded her to undergo mammography and that provided information about her specific lifetime risk of developing invasive breast cancer as a percentage based on the National Cancer Institute's self-administered questionnaire [27].
The health education plus on-site mobile mammography intervention used all the educational components mentioned earlier and also offered women the opportunity to undergo breast cancer screening at the on-site mammography unit after the presentation. As a result of Medicare and commercial insurance and state-supported programs for low-income women, none of the participants in either arm of the study had to pay for the mammographic examination.
Objective
The objective of this randomized clinical trial was to compare the
mammography screening rate of older women with access to a mobile mammography
unit and an educational outreach program with the screening rate of older
women with access to an educational outreach program only. We hypothesized
that providing on-site mammography would lead to a statistically significant
and clinically meaningful increase in the breast cancer screening rate beyond
that of health education alone.
Outcome
The primary outcome was the participants' responses about whether they had
undergone mammography during the 3 months after the intervention. During
telephone interviews, participants were asked "Have you had a mammogram
since the UCLA woman's health program on [the date of the program]?" The
use of participants' responses (self-reporting) regarding mammography has been
verified as an accurate measure that includes older women and women from
low-income households [15,
28,
29].
Sample Size
The sample size was designed to detect a 15—percentage-point
difference in mammography screening rates with a power of 0.80 using a
two-tailed test with an alpha value of 0.05. The initial sample size was
increased by 22% because of the cluster design and to allow attrition. After
these adjustments, the study needed to recruit 230 subjects in each arm of the
study to achieve this level of power.
Randomization
Sites for the intervention were recruited sequentially over 24 months. Each
site was matched with another site on the basis of the type of site (e.g.,
meal site, clubs, seniors' group) size, and location, ethnic, or socioeconomic
population served. The sequence generation was determined using a computer
program that randomly assigned the sites in each pair to one of the two study
arms. Allocation concealment was ensured because the computer assignment was
generated for each pair only after both sites had been recruited.
Implementation of the allocation sequence was performed by a research
associate. Once a site was assigned an intervention, all participants at that
site were assigned to that arm of the study.
Blinding (Masking)
Before the day of the health education program, participants were unaware
of which intervention their site had been assigned. On the day of the program,
the presence or absence of the mobile mammography van revealed to participants
which intervention group they had been assigned. For the same reason, the
research associates administering the interventions also were aware of
participants' intervention status. However, the outcomes assessor was unaware
of the intervention group status of all participants.
Statistical Methods
The analysis focused on comparing 3-month self-reported mammography rates
of the group who had the opportunity to undergo on-site mobile mammography in
addition to health education compared with those who received health education
alone. These comparisons included bivariate analyses (chi-square test) and
multivariate logistic regressions of receiving mammography within 3 months
after the intervention (dependent variable) on the intervention after
controlling for any differences between intervention groups on baseline
sociodemographic or health status covariates (independent variables). The
primary analysis also adjusted for correlation of observations within sites
(cluster effect) using the Huber method
[30], a nonparametric
correction for the independence of observations when estimating the sample
variance. These robust variances were used in the statistical tests that were
performed for the logistic analyses. To identify subgroups of patients for
whom the intervention was particularly useful, we conducted stratified
bivariate analyses of age, income, ethnicity, membership in a health
maintenance organization (HMO), previous mammography history, and breast
cancer risk. All analyses presented are by intent-to-treat assignment (i.e.,
intervention group). Analyses were conducted using computer software (Stata
[version 7.0]; Stata, College Station, TX), and p values of less than
0.05 were considered statistically significant.
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Recruitment
Participants were recruited between October 1998 and September 2000.
Follow-up of subjects was completed by December 2000.
Baseline Data
Demographic and clinical characteristics of participants in both groups are
presented in Table 1. Baseline
characteristics of both groups were similar except a higher percentage of
women in the health-education-only group had high school or more education
(87% vs 76%, p = 0.001). Ethnic minorities constituted almost half of
the sample. Approximately two thirds had an annual household income of less
than $20,000. Almost two thirds were members of HMOs. Approximately 20% in
each group last underwent mammography 5 or more years ago or had never
undergone this test.
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Numbers Analyzed
The primary analysis was intention-to-treat and involved all participants
who were randomly assigned. In the group offered mobile mammography and health
education, 17 were lost to follow-up and in the group offered health education
only, 19 were lost to follow-up (Fig.
1), leaving 235 and 228 in the two groups, respectively, for
analysis.
Outcomes and Estimation
Women in the group offered mobile mammography and health education were
significantly more likely than those offered health education only to report
undergoing mammography within 3 months of the interventions (55% vs 40%,
p = 0.001) (Table 2).
After adjustment for correlation of observations at the site level (cluster
effect), this effect was still significant (adjusted odds ratio, 1.83; 95%
confidence interval [CI], 1.22-2.74). Further adjustment for level of
education, which was imbalanced in the randomization, did not alter the
estimate (adjusted odds ratio, 1.81; 95% CI, 1.21-2.71). Of the 129 women in
the mobile mammography intervention arm who reported receiving mammography
within 3 months, 120 (93%) had this test performed at the mobile unit that was
available during the Senior Women's Health Day.
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Ancillary Analyses
Table 2 presents bivariate
analyses by sub-group. Self-reported mammography rates were significantly
higher for women assigned to the mobile mammography plus health education
intervention compared with the health education only intervention for women in
the following subgroups: age of 65-74 years; age of 75-84 years; household
income of less than $20,000; Asian American women; Hispanic women; HMO
members; women whose last mammogram was 2 or more years ago or who had never
undergone mammography; and women with a score for lifetime risk of breast
cancer that was below the median score. Among women who had never undergone
mammography, nine (33%) of 27 women in the mobile mammography arm of the study
compared with two (12.5%) of 16 in the health education arm of the study
reported receiving screening within 3 months of the intervention.
Adverse Events
No adverse events were noted in the trial.
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This study builds on previous research about using mobile mammography to increase mammography use among older women. Rimer et al. [15] developed and tested a multistrategy health education program designed to reduce the cost, access, knowledge, and belief barriers to older women in retirement communities. In addition to patient education, a mobile mammography van was available to the experimental group. During the 3-month follow-up period, 45% of the experimental group compared with 12% of the control group reported undergoing mammography. However, the design of the study was unable to separate the effect of accessibility of the mobile unit from the effect of receiving health education.
In our present study, the health educational program was comprehensive including a variety of techniques that were effective in previous studies (e.g., in-person counseling, follow-up letters, exemplary beads) [17, 26]. However, access to on-site mammography was clinically and statistically more effective in achieving mammography screening than these patient education methods alone. In our study, the effectiveness of on-site mammography likely resulted from its ability to overcome barriers that prevent older women from receiving this preventive examination, including immobility [32] and inconvenience.
Our results about the effectiveness of offering on-site mammography to women in ethnic minority groups are consistent with those of previous studies about the factors related to women in minority groups who choose to not undergo screening mammography. For example, among black women, forgetting the date of the mammography appointment [33] was an important factor. Moreover, our findings are also consistent with results of a clinical trial that found that women who were given the option to undergo mammography the same day as their physician office visit were more likely to receive breast cancer screening within 3 months than those receiving traditional care [34]. In that study, the availability of sameday mammography was particularly effective among women 65 years old or older.
These studies and our findings suggest that once a woman decides to undergo mammography, the ability to do so immediately facilitates adherence. In addition, peer-group pressure likely influenced women in our study to undergo mammography at the same time as other attendees at the sites.
Generalizability
Although the study recruited a diverse sample of women including almost
half from ethnic minority groups and a majority with a low income, several
issues related to generalizability must be considered. First, these women
agreed to participate in a study, and such volunteers may not be
representative of the entire population. Second, the study was conducted in
one geographic area, and the effectiveness of offering access to a mobile
mammography unit in other communities may differ. Third, to prevent
differential enrollment across study arms, we did not inform the women
attending the sites where mobile mammography would be available in advance.
Advance notice has been identified as important in focus groups of inner city
health center patients [35].
Accordingly, our mobile mammography intervention may have been less effective
than under real-life circumstances. Fourth, our power to detect differences
among subgroups was limited. Nevertheless, self-reported screening rates were
higher for women who were offered on-site mammography for every subgroup we
examined in the study except among women who were 60-64 years old. Smaller
increases in mammography use, or fewer participants in some subgroups,
resulted in differences that may have been clinically meaningful but that were
not statistically significant (e.g., a 14% difference between treatment arms
among black participants and a 15% difference among participants who were not
HMO members). Finally, the health education program was standardized across
ethnic groups, although it was presented in Spanish as well as English at some
sites. Health education interventions developed for specific ethnic groups
might be more effective than ours was, thereby reducing the differences
between the breast cancer screening rate for women offered mobile mammography
and health education versus that for women offered health education only.
In summary, this study provides strong support for the effectiveness of offering mobile mammography at community-based sites where older women gather as a method to increase breast cancer screening rates among older women. The effectiveness of this strategy is greater than what can be accomplished using only a multifaceted health education program. Moreover, offering access to on-site mammography in addition to health education seems to be particularly effective for subgroups of women who traditionally have had low screening rates. The cost-effectiveness of this approach and specific factors that influenced women to undergo on-site mammography remain to be determined.
Acknowledgments
We thank Gail Greendale, Emmett Keeler, and Annette Maxwell for reading a
draft of the manuscript and Kathleen Adams, Janice Chernoff, and Daniel
Millner for collecting data and administering the interventions.
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