Journal of the National Cancer Institute Advance Access originally published online on February 26, 2008
JNCI Journal of the National Cancer Institute 2008 100(5):347-358; doi:10.1093/jnci/djn026
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© The Author 2008. Published by Oxford University Press.
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Promoting Regular Mammography Screening II. Results From a Randomized Controlled Trial in US Women Veterans
Affiliations of authors: Division of Health Promotion and Behavioral Sciences, University of Texas-Houston School of Public Health, Houston, TX (SWV, SPC, WC, DRL, AM, MEF, AH); Center for Clinical and Translational Sciences, University of Texas Health Science Center, Houston, TX (DJdJ); Cancer Prevention Fellowship Program, Office of Preventive Oncology, Division of Cancer Prevention, National Cancer Institute, Bethesda, MD (JAT); University of Houston-Victoria, Victoria, TX (CAP); Center for Health Services Research in Primary Care, Durham Veterans Health Administration/Duke University, Durham, NC (LAB); Department of Community Health, Brown University, Providence, RI (WR); School of Math, Science & Technology, Elizabeth City State University, Elizabeth City, NC (CW); Department of Psychology, University of Maryland Baltimore County, Baltimore, MD (CD)
Correspondence to: Sally W. Vernon, PhD, Division of Health Promotion and Behavioral Sciences, University of Texas-Houston School of Public Health, 7000 Fannin, Ste 2560, Houston, TX 77030 (e-mail: sally.w.vernon{at}uth.tmc.edu).
Background: Few health promotion trials have evaluated strategies to increase regular mammography screening. We conducted a randomized controlled trial of two theory-based interventions in a population-based, nationally representative sample of women veterans.
Methods: Study candidates 52 years and older were randomly sampled from the National Registry of Women Veterans and randomly assigned to three groups. Groups 1 and 2 received interventions that varied in the extent of personalization (tailored and targeted vs targeted-only, respectively); group 3 was a survey-only control group. Postintervention follow-up surveys were mailed to all women after 1 and 2 years. Outcome measures were self-reported mammography coverage (completion of one postintervention mammogram) and compliance (completion of two postintervention mammograms). In decreasingly conservative analyses (intention-to-treat [ITT], modified intention-to-treat [MITT], and per-protocol [PP]), we examined crude coverage and compliance estimates and adjusted for covariates and variable follow-up time across study groups using Cox proportional hazards regression. For the PP analyses, we also used logistic regression.
Results: None of the among-group differences in the crude incidence estimates for mammography coverage was statistically significant in ITT, MITT, or PP analyses. Crude estimates of compliance differed at statistically significant levels in the PP analyses and at levels approaching statistical significance in the ITT and MITT analyses. Absolute differences favoring the intervention over the control groups were 1%–3% for ITT analysis, 1%–5% for MITT analysis, and 2%–6% for the PP analysis. Results from Cox modeling showed no statistically significant effect of the interventions on coverage or compliance in the ITT, MITT, or PP analyses, although hazard rate ratios (HRRs) for coverage were consistently slightly higher in the intervention groups than the control group (range for HRRs = 1.05–1.09). A PP analysis using logistic regression produced odds ratios (ORs) that were consistently higher than the corresponding hazard rate ratios for both coverage and compliance (range for ORs = 1.15–1.29).
Conclusions: In none of our primary analyses did the tailored and targeted intervention result in higher mammography rates than the targeted-only intervention, and there was limited support for either intervention being more effective than the baseline survey alone. We found that adjustment for variable follow-up time produced more conservative (less favorable) intervention effect estimates.
| CONTEXT AND CAVEATS Prior knowledge Some behavioral interventions, especially those that include individually tailored messages, have been found to increase rates of one-time mammography screening. However, fewer studies have analyzed interventions to promote ongoing regular mammography. Study design The Project Healthy Outlook on the Mammography Experience trial compared rates of completion of two or more mammograms ("compliance") among women randomly assigned to a tailored and targeted intervention, to a targeted intervention, and to a survey-only control group. Outcomes were evaluated by three decreasingly conservative analytic methods. Contributions An analytic approach that takes losses to follow-up into account may produce more conservative (less favorable) estimates of intervention effects. Only the least conservative analysis provided evidence that either intervention improved compliance compared with the survey-only control group. The absolute between-group difference ranged from 3% to 6%, depending on the analysis. Implications An intervention targeted to a broad group of women (in this case, women veterans) may work as well as one that is both tailored and targeted, although neither intervention was clearly superior to the control condition. Limitations The appropriate analytic method for a study of this type is not clear. The study did not have the statistical power to evaluate whether the modest intervention effects that were observed were statistically significant. It was possible to assess the validity of results based on self-reported mammography by reviewing medical records only for the subgroup of women veterans known to have ever used Veterans Healthcare Administration facilities. A longer follow-up may be necessary to evaluate compliance among women who have regular mammograms at intervals of more than 2 years.
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Manuscript received August 7, 2007; revised December 7, 2007; accepted January 17, 2008.
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