Breast cancer can resurface after remaining dormant for 15 years following successful treatment, a study has found.
Women with large tumours and cancer that had spread to the lymph nodes had the highest 40% risk of it coming back.
Researchers writing in the New England Journal of Medicine said extending treatment with hormone therapy could reduce the risk of it recurring.
Scientists analysed the progress of 63,000 women for 20 years.
All had the most common form of breast cancer.
This is a type fuelled by the hormone oestrogen which can stimulate cancer cells to grow and divide.
Every patient received treatments such as tamoxifen or aromatase inhibitors which block the effects of oestrogen or shut off the hormone’s 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 who originally had large tumours and cancer that had spread to four or more lymph nodes were at highest risk of the cancer returning the next 15 years, the study said.
Women with small, low-grade cancers and no spread to the lymph nodes had a much lower 10% risk of cancer spread over that time.
Why you should get it checked often
Treatment can be more effective when cancer is found early. Keep an eye out for any unusual changes to your body, such as:
- lumpiness or a thickened area in your breasts, any changes in the shape or colour of your breasts, unusual nipple discharge, a nipple that turns inwards (if it hasn’t always been that way) or any unusual pain.
- a lump in the neck, armpit or anywhere else in the body.
- sores or ulcers that don’t heal.
- coughs or hoarseness that won’t go away or coughing up blood.
- changes in toilet habits that last more than two weeks, blood in a bowel motion.
- new moles or skin spots, or ones that have changed shape, size or colour, or that bleed.
- unusual vaginal discharge or bleeding.
- unexplained weight loss.