Breast cancer can resurface after remaining dormant for 15 years following successful treatment , a study has found.
Women's with large tumours and cancer that had spread to the lymph nodes had the highest 40%. Risk of its coming back.
Researchers writing in the new England journal of medicines said extending treatment with hormone therapy could reduce the risk of its recurring .
Scientists analyze the progress of 63,000 women for 20 years.
All had the most common form of breast cancer.
This is a type of fuelled by the hormone oestrogen which can stimulate cancer cells to grow and divide.
Every pateint receives such as tamoxifen or aromatase inhibitors which Block the effects of oestrogen or shut off the hormones supply.
Although after five years of treatment their cancers had gone , over the next 15 years a steady number of women found that their cancer spread throughout their body some up to 20 years after diagnosis.
Women with small, low- grade cancer and no spread to the lymph nodes had a much lower 10% risk of cancer spread over that time.
' Remarkable '
Lead researcher Dr Hongchao pan, from university of Oxford , said it is remarkable that breast cancer can remain dormant for so long and spread many years laters, with this risk
Remaining the same year after year and still strongly related to the site of the original cancer
And whether it spread to the lymph nodes.
Doctor have long known that five years of tamoxifen reduce the risk of recurrence by about a third in the five years after stopping treatment
Recent research has suggested that extending hormone therapy to 10 years may be more effective at preventing the breast cancer recurrence and death.
(Breast cancers cell's are stimulated to grow and divide by the hormone oestrogen)
Aromatase inhibitors which only work for post - menopausal women, are believed to be even more effective.
But there are side effects with hormone treatment which can Affect patient quality of life and cause them to stop taking the pills .
These include menopausal symptoms , osteoporosis , joint pain and carpal tunnel syndrome.
Professor Arnie purushotam
, Senior clinical advisor at cancer research UK, which funded the study, said that since the research vegans, new drugs had been used to treat breast cancer and thosed worked in different ways to tamoxifen.
He said it's vital that worked continues to better predict which cancers might return.
We also need to know
What the difference for women might be taking in hormone therapies for 10 years instead of five, the side effects and how this affects patients quality of life.
Sally greenbook, from charity breast cancer Now, said it was essential that women discussed any changes in treatment with their doctor.
We would like to urge all women who have treatment for breast cancer not to be alarmed but to be ensured they are aware of the signs of recurrence and of metastatic breast cancer , and to speak to their Go or breast care team if they have any concerns.