Experts believe a lack of clinical trials aimed at younger breast cancer patients could be partly to blame for longer-term survival problems.
The study, funded by Cancer Research UK and the Wessex Cancer Trust, analyzed nearly 3,000 women under 40 in the UK with diagnosed breast cancer.
It found a rapid rise in relapse after five years in younger patients with a certain type of the cancer.
This contrasts with what normally happens with the disease.
Experts believe a lack of clinical trials aimed at younger breast cancer patients could be partly to blame for longer-term survival problems
The data, published in the Journal of the National Cancer Institute, showed that survival five years after diagnosis was 85%. By the eight-year mark it was 68%.
Breast cancer is mostly diagnosed in post-menopausal women, although those with a diagnosis under 40 represent fewer than 5% of all breast cancers treated in the UK.
The study looked at cases involving oestrogen-receptor-positive disease, whose cancers are fuelled by the female hormone oestrogen.
This form of the disease is usually treated by chemotherapy followed by the drug tamoxifen for five years to block oestrogen receptors.
Researchers suggested that taking tamoxifen for a longer period may help, but they said the underlying problem was that trials needed to involve more younger patients.
Chief investigator Prof. Dianna Eccles said: “This study adds to the evidence that breast cancer can behave very differently when diagnosed in younger women.
“They may require a different approach to treatment, which isn’t necessarily understood from cancer trials in older patients.”
Thousands of healthy women could be offered powerful breast cancer drugs to cut their chances of contracting the disease.
New guidelines suggest the drugs raloxifene (Evista) or tamoxifen (Nolvadex, Istubal or Valodex) could offer as much as 20 years of protection for those considered at high risk of cancer.
The aim is to slash the odds of developing breast cancer in the first place – just as statins are given to patients to stave off heart disease.
Even women judged to be at “moderate” risk of the disease in the next ten years, due to genetic or family history, could be given daily medication.
Charities have hailed the new guidance as an “historic step” in the treatment of breast cancer.
Tamoxifen has been used to treat the illness for more than 30 years, saving the lives of hundreds of thousands at a cost of just a few pennies a day, although newer drugs are proving even more effective.
International trials show it reduces the risk of the most common kind of breast cancer by one third after five years, with the preventative effect lasting up to 20 years.
The guidelines are released today by the National Institute for Health and Clinical Excellence (NICE), the watchdog responsible for advising the UK’s National Health Service (NHS) on good practice.
New guidelines suggest the drugs raloxifene or tamoxifen could offer as much as 20 years of protection for those considered at high risk of breast cancer
Women would take the drugs for five years either before or after menopause.
Currently in the UK, high-risk women can be offered annual MRI scans from the age of 40 and may decide to have preventative surgery, including mastectomies (the removal of their breasts).
The guidance says that more women at higher than average risk should be offered surveillance at a younger age to detect the disease earlier.
The risk of breast cancer in the general population is one in eight – but this rises to one in three for women at high risk and one in four for those at moderate risk.
In the U.S., nearly 300,000 cases of breast cancer are reported each year.
More than two-thirds of those cases
Almost 50,000 women a year are diagnosed with breast cancer.
Women with faulty genes such as BRCA1, BRCA2 and TP53 are among those who have a more than 80 per cent chance of being diagnosed with the disease.
Both tamoxifen and the osteoporosis drug raloxifene, which is used after menopause, are licensed in the U.S. for breast cancer prevention but are not widely taken up, partly because of concerns about possible side effects.
The National Institute for Health and Clinical Excellence says the drugs are being recommended because they have “good evidence” behind them.
Breast cancer specialist Professor Michael Baum said the drugs were a “reasonable option” for women at high risk because of evidence that they cut the death rate.
He said: “I don’t think women or doctors will be deterred from using them by the lack of a license.
“NICE’s support for preventive drugs could encourage clinicians, it will give them more confidence when talking to women at high risk about their options.”
