Postmenopausal hormone therapy and prevalent round screening mammography

Abstract

BreastCheck, the Irish National Breast Screening Programme completed its prevalent round of screening in December 2002. There was concern regarding the influence of postmenopausal hormone therapy (PHT) on the effectiveness of the screening process during the prevalent round based on 2 high-profile studies, which have subsequently been published.1, 2 The prevalent round met its objectives including a participation rate of 73%, a recall rate of <7% and a cancer detection rate of 9.8/1,000 women screened; however, the influence of PHT was unknown. Participants completed a questionnaire at the time of mammography regarding PHT use. Herein, we describe the pattern of PHT use among women attending a single screening center and its impact on recall during prevalent round screening. Between February 2000 and December 2002, 46,375 women underwent screening mammography at the Eccles center (75% of invited population). Forty-two percent of these women had a history of PHT use and 26% of women were taking PHT at the time of screening mammography. ‘The recall rates, biopsy rates and breast cancer incidence are shown in Tables I & II.’ We observed an increased false-positive recall among women with a history of PHT use. This phenomenon has been observed in studies such as the Million Women Study.3 The false-positive recall rate in a screening program reduces with each round subsequent to the prevalent round4 although it does not appear to differ between first and subsequent rounds in established screening programs.3 This is the first report to our knowledge of the influence of PHT on prevalent round mammography. Women with a history of PHT use did not have a higher incidence of screen-detected cancer; however, we cannot comment on the effect of PHT on the overall incidence of breast cancer, as symptomatic cancers would have been selected out before the women entered the screening program. We observed a more favorable histological type of cancer among the women with a history of PHT use. This may reflect an influence of PHT on less favorable tumor types causing an earlier and symptomatic presentation rather than a time-increased incidence of this secondary to PHT (although this has been suggested in other studies). We did not differentiate between types of HRT for 2 reasons. First, at the time of study inception there was no evidence that the type of PHT influenced breast cancer incidence, and second, women's recall of type of PHT is often inaccurate.5 Although PHT has been demonstrated to increase the risk of false-positive recall, hormonal constituents do not appear to influence this risk.3 These findings need to be taken into account before starting a population-based screening program. We use false-positive recall as a marker for quality assurance, and higher rates of PHT use among women undergoing prevalent round screening could negatively influence the quality assurance process. Whether PHT will have as great an effect in subsequent rounds needs to be addressed. Yours sincerely, Karl J. Sweeney, Sinead Boran, Patricia Fitzpatrick, Ann B. Merrigan, Ronan Moran, Fidelma Flanagan, Michael J. Kerin.