The first Australian data on the long term risk of distant metastases in breast cancer will help patient discussions about prognosis and treatment options, researchers say.

The risk of breast cancer distant metastases peaks in the second year and reduces with time to 1% in the fifth year after the initial diagnosis, lower than previously reported, according to findings from the University of Notre Dame and the NHMRC Clinical Trials Centre, Sydney University..

The Australian population-based study of health records, published in the Medical Journal of Australia, found the risk of distant metastases declined in the years after the initial non-metastatic diagnosis to 1% per year for localised cancer at five years and 2% for regional cancer after seven years.

Lead author Associate Professor Sally Lord, from The University of Notre Dame’s School of Medicine, said findings could inform discussions with patients about the risk of distant metastases (DM) and death from the condition.

“Australian population cancer recurrence rates have not been previously available for discussions with patients but this information is incredibly important,” she said.

“Breast cancer consumer groups like Breast Cancer Network Australia and Cancer Voices have been demanding this information for many years to help counsel patients. It is well documented that many patients live with a fear of recurrence and would be reassured to understand the long-term risk reduces with time since diagnosis; others who experience a recurrence after successfully completing treatment have expressed regret that they were not aware of the small risk about this possibility.”

The annual risk of dying from breast cancer was 36% in the first year, and 14% in the fourth year after DM detection. Likewise, the distant metastases risk declines with time from the diagnosis of nonmetastatic breast cancer.

The researchers conducted a retrospective cohort study based on health records for women aged 18 years and older who were diagnosed with invasive breast cancer throughout 2001 and 2002, as registered in the NSW Cancer Registry. There were 6338 women diagnosed throughout that period.

The study assessed the time from the initial diagnosis to the first distant metastases, and from the first distant metastases to death from breast cancer. The secondary outcome was the time from the first metastases to death from any cause.

It found the 14-year cumulative incidence of distant metastases was 22.2% overall within 14 years, with those who had localised breast cancer 14.3% and regional breast cancer 34.7%.

“The annual hazard of breast cancer death peaked for women in all age groups with localised and regional disease at diagnosis two to three years after diagnosis. The annual hazard of death from other causes (localised and regional breast cancer groups combined) increased with time,” the authors noted.

In perspective

Associate Professor Lord said internationally, a 30% long-term risk was commonly cited but poorly referenced. The change in recurrence risk over time following diagnosis was not widely discussed with patients, she said.

“The paper includes this information and helps put the size of risk in perspective by showing it alongside the risk of death due to other causes which increases as we age,” she told the limbic.

The study also found prognosis was lowest for women aged over 70 years or older at the time of their first distant metastases, but survival time varied significantly.

“Overall median survival was 23 months (IQR, 6–88 months), but 29% of women were alive five years after DM detection. That the annual risk of breast cancer death declined with time from the first DM record is probably explained by the heterogeneity of metastatic breast cancer: some people have aggressive disease that leads to death within two years, others have more indolent, treatment-responsive disease and live longer than five years.

“Our findings illustrate the importance of adjusting prognostic information according to the number of event-free years and accordingly revising discussions with patients over time.”

Associate Professor Lord said the variance may surprise clinicians, as was the finding that higher risk of distant recurrence for oestrogen receptor negative cancer reduced to the same level as estrogen receptor positive cancers over five years.

The population study also showed the DM risk for women who were diagnosed more recently was “probably lower” than reported, given the release and PBS listing of newer treatments, noting international studies that have found declining risk over time. These include the 2004 listing of aromatase inhibitors and 2006 listing of trastuzumab.

“Major treatment advances have been introduced for people with breast cancer to reduce the risk of recurrence; and improve survival after recurrence,” Associate Professor Lord said.

“This study provides benchmark information to track these improvements. While the size of the risk will be lower, I expect the pattern of changes in risk over time will remain similar and is valuable information to convey to patients attending follow up.​”