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Association of skirt size and postmenopausal breast cancer risk in older women: a cohort study within the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS)
  1. Evangelia-Ourania Fourkala1,
  2. Matthew Burnell1,
  3. Catherine Cox1,
  4. Andy Ryan1,
  5. Laura Currin Salter2,
  6. Aleksandra Gentry-Maharaj1,
  7. Mahesh Parmar3,
  8. Ian Jacobs1,4,
  9. Usha Menon1
  1. 1Department of Women's Cancer, Institute for Women's Health, University College London, London, UK
  2. 2University College London Hospitals NHS Foundation Trust, London, UK
  3. 3MRC Clinical Trials Unit, London, UK
  4. 4Academic Health Science Centre, University of Manchester, Manchester, UK
  1. Correspondence to Professor Usha Menon; u.menon{at}ucl.ac.uk

Abstract

Objectives Several studies suggest that overall and central-obesity are associated with increased breast cancer (BC) risk in postmenopausal-women. However, there are no studies investigating changes of central obesity and BC. We report on the association of BC risk with self-reported skirt size (SS; waist-circumference proxy) changes between 20s and postmenopausal-age.

Design Prospective cohort-study.

Setting UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) involving the nine trial centres in England.

Participants Postmenopausal-women aged >50 with no known history of BC prior to or on the day of completion of the study-entry questionnaire.

Interventions At recruitment and at study entry, women were asked to complete a questionnaire. Women were followed-up via ‘flagging’ at the NHS Information Centre in England and the Hospital Episode Statistics.

Main outcome-measure Time to initial BC diagnosis.

Results Between 2 January 2005 and 1 July 2010, 92 834 UKCTOCS participants (median age 64.0) completed the study-entry questionnaire. During median follow-up of 3.19 years (25th–75th centile: 2.46–3.78), 1090 women developed BC. Model adjusted analysis for potential confounders showed body mass index (BMI) at recruitment to UKCTOCS (HR for a 5 unit change=1.076, 95% CI 1.012 to 1.136), current SS at study entry (HR=1.051; 95% CI 1.014 to 1.089) and change in SS per 10 years (CSS) (HR=1.330; 95% CI 1.121 to 1.579) were associated with increased BC risk but not SS at 25 (HR=1.006; 95% CI 0.958 to 1.056). CSS was the most predictive singe adiposity measure and further analysis including both CSS and BMI in the model revealed CSS remained significant (HR=1.266; 95% CI 1.041 to 1.538) but not BMI (HR=1.037; 95% CI 0.970 to 1.109).

Conclusions CSS is associated with BC risk independent of BMI. A unit increase in UK SS (eg, 12–14) every 10-years between 25 and postmenopausal-age is associated with postmenopausal BC risk by 33%. Validation of these results could provide women with a simple and easy to understand message.

Trial registration number ISRCTN22488978.

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