Their concerns follow findings from the first study to examine the impact of vaginal oestrogen in women receiving aromatase inhibitors (AIs) for breast cancer, published on-line today in Annals of Oncology, by a team from the Royal Marsden NHS Foundation Trust in London.
AIs work by inhibiting the enzyme aromatase, which promotes the conversion of androgens to oestrogens in postmenopausal women. Breast cancer feeds off oestrogen, so reducing the circulating levels of the hormone as much as possible lessens the chance of the cancer recurring. The new AIs reduce circulating oestradiol by over 97%.
Around a fifth of patients on adjuvant AIs suffer from atrophic vaginitis a distressing skin condition of the genitals caused by lack of oestrogen. Many ask if they can use topical oestrogen to alleviate the symptoms as conventional HRT is not recommended.
Senior author Professor Ian Smith, Head of the Breast Unit at the Royal Marsden, said: "Using this vaginal form of oestrogen which, we found, increases systemic oestradiol levels, will counteract AI treatment. With long term use, women may be risking the chance that their cancer may return, although this is probably not an issue if oestrogen rises for only one to two months."
Using a sensitive radioimmunoassay that they developed to quantify even extremely low levels, the researchers measured serum oestradiol in six women on adjuvant AI therapy who had actively asked to use the vaginal oestradiol tablet Vagifem for severe symptoms of atrophic vaginitis. They also monitored a seventh patient with metastatic breast cancer who was using Premarin oestradiol cream. Measurements were taken at baseline, then
Contact: Margaret Willson
European Society for Medical Oncology