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Title:Case-control studies of vaginal and vulvar cancers and gynecologic screening: a SEER-Medicare analysis
Author(s):Osterbur, Elaina
Director of Research:Rosenblatt, Karin
Doctoral Committee Chair(s):Rosenblatt, Karin
Doctoral Committee Member(s):Douglas, Jeffrey A.; Rich, Robert F.; Armstrong, Jocelyn
Department / Program:Kinesiology & Community Health
Discipline:Community Health
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Vaginal cancer
vulvar cancer
gynecologic cancers
Pap smear
pelvic examinations
Surveillance Epidemiology and End Results Registries (SEER-Medicare)
Abstract:The efficacy of performing pelvic examinations and Pap smears screening (gynecologic screening) in older women has been strongly debated among researchers and policymakers. Because of the rare nature of invasive vaginal and vulvar cancers, few epidemiological studies have been performed on this group (Mabuchi, et al. 1985, Brinton, et al. 1990a, Brinton, et al. 1990b) to determine if gynecologic screening reduces the risk of invasive vaginal and vulvar cancers. Previous studies, that have been published, utilized simulated mathematical models and small case-control designs to determine the etiology of vaginal and vulvar cancers, rather than to determine the efficacy of gynecologic screening. This study utilized two large national population-based linked databases: the Medicare data set supported by the Centers for Medicare and Medicaid (CMS) and the Surveillance Epidemiology and End Results Registries (SEER) data set sponsored by the National Cancer Institute (NCI). The study cases included female Medicare beneficiaries with invasive vaginal and vulvar cancers diagnosed between 1991 and 1999 by the SEER Registries (representing approximately 14% of the United States population) who were 65 years or over and Medicare eligible. The age and residence matched controls were selected from a five-percent (5%) Medicare sample of female beneficiaries 65 years or older, who received care between 1991 and 1999, had not been diagnosed with cancer, and resided in the SEER areas. This matched case-control design utilized incident vaginal (N=328) and vulvar (N=1,103) cancer cases, respectively from the Surveillance, Epidemiology and End Results (SEER). The study identified vaginal (N=2,624) and vulvar (N=8,825) cancer controls that were matched on age and geographical location to the cases. This study included women, covered by Medicare, who were enrolled in both Parts A and B coverage. These two matched case-control studies compared cases of persons diagnosed with invasive vaginal or vulvar cancers with non-cancer controls who had not been diagnosed with cancer. The purpose was to investigate whether they had a history of gynecologic screening during the estimated combined duration of the pre-invasive detectable phase (PIDP) when screening is most beneficial, which occurs prior to the occult invasive phase (OIP) (Weiss, 1999). Stratified analysis suggested that Pap smear and pelvic examination screenings have a stronger negative association among regional (odds ratio (OR) 0.78, 95% CI 0.40-1.51), distant (OR 0.31, 95% CI 0.09-1.03) and unstaged (OR 0.86, 95% CI 0.43-1.70) invasive vaginal cancers. Similar findings were observed for vulvar cancers suggesting that gynecological screening reduced the risk of regional (OR 0.71, 95% CI 0.51-1.00), distant (OR 0.68, 95% CI 0.27-1.70) and unstaged (OR 0.77, 95% CI 0.37-1.59) cancer stages. Borderline significant results were observed among women with invasive vaginal distant stage disease, as well as invasive vulvar regional stage disease. These findings suggest that gynecological screening may be effective in reducing the risk of later stages of disease of both vaginal and vulvar cancers. Women aged 65-74, who had been screened, have a slightly significant decreased risk of vulvar cancer (OR 0.55, 95% CI 0.31-0.97). These findings suggest that screening is most effective in reducing invasive vulvar cancer among women aged 65-74 years old. Medicare gynecologic screening may be useful even in women who have had negative Pap smear results to reduce the risk of late-stage vaginal and vulvar cancers. This study was unique in that it utilized a larger population-based, matched case-control design that directly measured the effectiveness of these secondary prevention measures in women over the age of 65 years and serves to fill a gap in the current literature.
Issue Date:2013-02-03
Rights Information:2012 Elaina Osterbur
Date Available in IDEALS:2013-02-03
Date Deposited:2012-12

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