US women with metastatic breast cancer surviving longer

By Liz Meszaros, MDLinx
Published June 1, 2017

Key Takeaways

The number of women in the United States living with distant metastatic breast cancer (MBC) has increased, perhaps due to both the aging of the population as well as improvements in treatment, according to a population-based study, recently published online in Cancer Epidemiology, Biomarkers & Prevention.

“Even though this group of patients with MBC is increasing in size, our findings are favorable,” said lead researcher Angela Mariotto, PhD, chief of the Data Analytics Branch of the Division of Cancer Control and Population Sciences at the National Cancer Institute (NCI). “This is because, over time, these women are living longer with MBC. Longer survival with MBC means increased needs for services and research. Our study helps to document this need.”

Dr. Mariotto’s co-authors included researchers from NCI, the Metastatic Breast Cancer Alliance, and the Fred Hutchinson Cancer Research Center.

They used population-based data to estimate the prevalence of MBC, using back-calculation methods on data on US breast cancer mortality and survival from the Surveillance, Epidemiology and End Results (SEER) registries. With this method, it is assumed that each observed breast cancer death was a result of MBC, either de novo or a recurrence with metastatic disease.

By January 1, 2017, Dr. Mariotto and colleagues estimated that there will be 154,794 women living with MBC in the US, and that 3 of 4 women initially diagnosed with stage I-III breast cancer would later progress to MBC.

Over the years, the median and 5-year relative survival for de novo MBC increased, especially in younger women. Researchers estimated a 2-fold increase in 5-year relative survival rate from women diagnosed with de novo MBC between ages 15 and 49 years from 18% during 1992 to 1994, to 36% during 2005 to 2012.

Median survival for women diagnosed between ages 15 and 49 years increased from 22.3 to 38.7 months from 1992 to 1994 and 2005 to 2012. In women diagnosed between the ages of 50 and 64 years, it increased from 19.1 to 29.7 months during these periods.

Dr. Mariotto and colleagues also found that over 11% of women diagnosed between 2000 and 2004 who were under the age of 64 survived 10 years or more. They estimated that the number of women living with MBC increased by 4% from 1990 to 2000, and by 17% from 2000 to 2010; and project that this number will increase by 31% from 2010 to 2020.

The largest group of women with MBC (40%) are those who have been living with metastatic disease for 2 years or less, but 34% have lived for 5 years or more.

Dr. Mariotto stressed that because they included women with recurrence, their results give a more accurate estimate of the number of women living with MBC.

“These findings make clear that the majority of MBC patients, those who are diagnosed with non-metastatic cancer but progress to distant disease, have never been properly documented,” she said.

“This study emphasizes the importance of collecting data on recurrence at the individual level in order to foster more research into the prevention of recurrence and the specific needs of this growing population,” Dr. Mariotto concluded.

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