In the ESA-SRB 2015 opening plenary session today delegates heard from a world-renowned expert about how oestrogen can both cause and prevent breast cancer.
Giving the ESA Harrison Plenary Lecture Professor Dick Santen from the University of Virginia in the US said studies had shown that factors like early menarche, delayed first birth, late menopause and a high body mass index increased the risk of breast cancer.
Yet paradoxically, oestrogen therapy alone in the Women’s Health Initiative study reduced breast cancer risk by 23% at 13 years of follow-up.
He suggested that two different mechanisms were at play: oestrogen was involved in both the initiation and promotion of breast cancer, and also induced apoptosis in occult tumours too small to be detected by mammogram in post menopausal women.
To understand this further his team developed and validated two models to describe the life history of breast cancer.
They found that it took an average of 16 years for a de novo cancer to reach the detection threshold of mammography or MRI.
The effects of menopausal hormone therapy in women in the WHI study observed over 5 to 10 years primarily reflected actions on occult tumours too small to be diagnosed, Santen told delegates.
This suggested that the blockade of oestrogen metabolism may reduce breast cancer development, he said.
But we needed a novel method for detecting small occult breast cancers which had not yet reached the diagnostic threshold.
“Treatment of these small tumours with anti-oestrogen or aromatase inhibitors might be more effective than later treatment,” he told the audience.