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Women diagnosed with early invasive breast cancer are now more likely to become long-term survivors, as mortality risk from the disease dropped substantially since the 1990s, according to researchers.

Their population-based observational cohort study of more than 500,000 women diagnosed with early invasive breast cancer in England from 1993 to 2015 showed that women diagnosed in 2010-2015 had a 5-year cumulative mortality risk of 4.9% (95% CI 4.8-5.0).

By comparison, the 5-year mortality risk was 14.4% (95% 14.2-14.6) for women diagnosed in 1993-1999, reported Carolyn Taylor, PhD, of the University of Oxford in England, and colleagues.

Furthermore, the cumulative 5-year breast cancer mortality risk for women diagnosed from 2010-2015 was estimated as less than 1% for about one-third of women, depending on patient and disease characteristics. However, it was 60% or more for a very small percentage of women.

"The prognosis for women with early invasive breast cancer has improved substantially since the 1990s," Taylor and her colleagues wrote in . "Most can expect to become long term cancer survivors, although for a few the risk remains appreciable."

"Our study can also be used to estimate risk for individual women in the clinic," Taylor said in a . "It shows that prognosis after a diagnosis of early breast cancer varies widely. Patients and clinicians can use our results to estimate prognosis moving forward. In the future further research may be able to reduce the risk of dying from breast cancer even more."

For purposes of this analysis, Taylor and her colleagues collected data from England's National Cancer Registration and Analysis Service on 512,447 women who were diagnosed with early breast cancer there from January 1993 to December 2015 and followed until December 2020. Of these women, 60% had breast conserving surgery and the remaining 40% had mastectomy.

Although decreases in mortality rates occurred across nearly all groups of patients, the magnitude of reduction varied substantially between women with different combinations of patient and disease characteristics (including age, screening status, estrogen receptor status, number of positive nodes, and tumor size and grade). Focusing on the period of 2010-15 also allowed Taylor and her colleagues to consider HER2 status, which was not available for earlier calendar periods.

Depending on the combinations of these variables, most women (62.8%) diagnosed during that time period had low 5-year mortality risk, at less than 3%. Five-year mortality risk was less than 5% for 73.7% of these women, and less than 10% for 88%.

However, the 5-year mortality risk was appreciably higher for smaller groups of women: at least 20% for 4.6% of women diagnosed from 2010-2105, at least 40% for 0.7%, and 60% or more for 0.2%.

"These breast cancer mortality risks inform patients today about their likely prognosis," Taylor and her colleagues observed. "For example, the estimated five year breast cancer mortality risk for a woman aged 60 at diagnosis, with a screen detected tumour, size <20 mm, low grade, oestrogen receptor positive, HER2 negative, and node negative would be 0.2%. This is likely to provide her with reassurance about her prognosis."

"They can also be used to identify the groups of women for whom the risk of breast cancer mortality remains substantial," they added.

Taylor and her colleagues suggested there are several likely explanations for the extended survival of patients diagnosed with early invasive breast cancer. For example, over the period of the study, systemic therapies, including aromatase inhibitors and taxanes, have become established in clinical use, while surgery and radiotherapy have become better targeted.

"This observational study cannot determine the specific causes of these reductions in mortality," they wrote. "However, the main aim of our study was not to quantify the causal role played by different factors in the observed decreases in the breast cancer mortality rate. Instead, we provide information for clinicians to use when estimating breast cancer mortality risks for patients today."

An accompanying by Taylor, a co-author, and two breast cancer survivors involved in the study as patient advocates emphasized that physicians must tell their patients that a breast cancer prognosis will vary widely depending on the risk factors described in the study.

"When I was diagnosed 20 years ago, I was not given a prognosis other than the fact that this is serious and we need to treat you quickly," said patient advocate Mairead MacKenzie. "But I think good, clear communication about prognosis can make a vast difference to a patient's quality of life, and how they can cope with things."

"For the majority of women, the prognosis is good," she added. "This study backs that up and gives reassurance -- because, initially, everybody thinks they're going to die."

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