Thirty years ago, Lesley Laxton, a 53-year-old dentist from Colchester, received an invitation to attend a routine NHS breast screening. Alongside the invitation was a letter from Professor Dame Valerie Beral asking her to participate in a new study investigating the links between hormone replacement therapy (HRT) and breast cancer risk.
At the time, more and more women in the UK and elsewhere were taking HRT to relieve menopausal symptoms amid claims it could improve their general wellbeing and life expectancy. But emerging evidence from small studies suggested that HRT might increase women’s risk of breast cancer.
In search of some definitive data, Beral and her team at the Oxford Cancer Epidemiology Unit (now part of Oxford Population Health) set out to recruit a million women in their 50s and early 60s who they could track for a number of years through regular questionnaires and NHS records. Between 1 May 1996 and 2001, some 1.3 million women – a quarter of all UK women between 50 and 64 – filled in the recruitment questionnaire and brought it to their breast screening appointment. Among them was Laxton.
As well as looking at the associations between HRT use and breast cancer risk, the Million Women Study would provide the first opportunity to investigate how changes in behaviour and lifestyle had affected the long-term health of this generation of women.
As most diseases become more common after middle age, the researchers also understood the value of targeting this age group of women, recalls Professor Gill Reeves, the current Director of the Cancer Epidemiology Unit, who was working as the study’s statistician at the time.