Women diagnosed with early stage breast cancer in 2010-2015 were around 66% less likely to die from the disease within 5 years of diagnosis than they were 20 years earlier, according to data from a new study led by researchers from Oxford University and published in the BMJ. "Most women diagnosed with early breast cancer can expect to become long-term survivors," said the researchers.
While the risk of dying from early breast cancer was known to have decreased over the past few decades, the extent of the decrease was previously unknown, and it was not known whether it applied to all women or only to groups with certain characteristics.
To address this uncertainty, researchers used data from the National Cancer Registration and Analysis Service to investigate the long-term mortality risks after a diagnosis of early breast cancer.
They included all 512,447 women registered in England from January 1993 to December 2015 with early breast cancer as their first cancer, and who were treated initially with surgery.
They estimated annual breast cancer death rates and cumulative 5-year risks, taking account of time since diagnosis, calendar period of diagnosis, and characteristics such as age, whether the cancer was detected by screening, involvement of lymph nodes, and tumour size and grade. All women were followed until December 2020.
Results showed that for women with a diagnosis made within each of the calendar periods 1993-99, 2000-04, 2005-09, and 2010-15, the annual breast cancer mortality rate was highest during the five years after diagnosis and then declined.
Cumulative 5-Year Mortality Rate Progressively Declined
Cumulative 5-year breast cancer mortality risk was on average 14.4% for women with a diagnosis made during 1993-99, but fell to 4.9% for women diagnosed during 2010-15.
Overall, for the 156,338 women diagnosed during 2010-15, more than six in 10 (62.8%) women had a 5-year risk of 3% or less, the team said. However cumulative 5-year breast cancer mortality risk varied substantially according to patient age, whether or not the cancer was detected by screening, receptor status, tumour size and grade, and lymph node involvement. Risk was more than 20% for 4.6% of these women.
The researchers concluded that the "substantial fall in risk of death from breast cancer since the 1990s" should provide reassurance for patients and doctors, as well as providing "estimates of their likely prognosis based on up-to-date data". Most women treated for early breast cancer can be informed they are likely to become long term cancer survivors, while the results can also help to identify those for whom the risk remains substantial.
Study 'Good News' for the Majority of Women
In a statement, Michelle Mitchell, chief executive of Cancer Research UK, which part-funded the study, said: "It's heart-warming news that women today have more time with their families and loved ones after an early breast cancer diagnosis. Receiving any cancer diagnosis is an extremely worrying time, but this study can give patients a more accurate prognosis and offer reassurance for many women."
Lead author Carolyn Taylor, professor of oncology at Oxford Population Health, said: "Our study is good news for the overwhelming majority of women diagnosed with early breast cancer today because their prognosis has improved so much."
In a linked opinion piece, patient advocates Mairead MacKenzie and Hilary Stobart, who contributed their data to the study, stressed that "doctors need to help patients understand that breast cancer is 'not all one thing'. Prognosis varies widely according to risk factors such as tumour size, lymph node involvement and whether the tumour was detected by screening", they said.
Ms Stobart pointed out that many women diagnosed with breast cancer might have less than 1% risk of dying from breast cancer at five years.
"Initially, everybody thinks they're going to die," Ms MacKenzie said. But "for the majority of women, the prognosis is good".
Asked to comment by Medscape News UK, Baroness Delyth Morgan, chief executive at Breast Cancer Now welcomed the research. She said the results were "testament to significant progress made on breast cancer research over the decades, including advances in diagnosis and treatment".
She continued: "But we must be clear, breast cancer is not a done deal – 11,500 people a year in the UK die from the disease, and despite the tireless work of NHS staff, we know many women are waiting far too long for a diagnosis and are experiencing anxious delays to their treatment. Without urgent action from governments across the UK to get breast cancer services back on track, we risk seeing these decades of progress unravelling."
The study was funded by Cancer Research UK, the National Institute for Health Research Oxford Biomedical Research Centre, and the University of Oxford.