New data suggests the number of women in the U.S. living with distant metastatic breast cancer is growing. As of the beginning of this year, that number was more than 150,000, according to new research from NCI published online ahead of print in the journal Cancer Epidemiology, Biomarkers & Prevention (2017; doi:10.1158/1055-9965.EPI-16-0889).
The researchers analyzed data from the NCI's Surveillance, Epidemiology, and End Results Program to determine how many women diagnosed with breast cancer went on to develop metastatic disease. (The researchers applied a back-calculation method to breast cancer mortality and survival data.) It is the first estimate of its kind to include both women initially diagnosed with metastatic breast cancer, as well as those who progress to the disease after a first diagnosis at an earlier stage (because U.S. registries currently do not routinely collect or report on recurrence data).
The estimates suggest the number of women living with metastatic breast cancer grew by 4 percent from 1990 to 2000 and 17 percent from 2000 to 2010. The researchers project that number will increase by 31 percent from 2010 to 2020.
The growing number, however, is a favorable finding, the study's lead author Angela Mariotto, PhD, Chief of the Data Analytics Branch of the Division of Cancer Control and Population Sciences at the NCI, explained. "Over time, these women are living longer with [metastatic breast cancer]. Longer survival with [metastatic breast cancer] means increased needs for services and research. Our study helps to document this need."
The data also revealed that the median and 5-year relative survival for women initially diagnosed with metastatic breast cancer is improving-particularly among younger women.
As of Jan. 1, 2017, more than 150,000 women in the U.S. were currently living with metastatic breast cancer-and three out of four of them had initially been diagnosed with an earlier stage breast cancer. Between 1992 to 1994 and 2005 to 2012, 5-year relative survival among women initially diagnosed with metastatic breast cancer between the ages of 15 and 49 doubled from 18 percent to 36 percent. And more than 11 percent of women diagnosed between 2000 and 2009 who were younger than 64 survived at least 10 years.
"These findings make clear that the majority of [metastatic breast cancer] patients, those who are diagnosed with non-metastatic cancer but progress to distant disease, have never been properly documented," Mariotto added. "This study emphasizes the importance of collecting data on recurrence at the individual level to foster more research into the prevention of recurrence and the specific needs of this growing population."
Here's what else Mariotto told Oncology Times about the new data.
1 Why was this group of women with cancer never accurately documented before?
"Approximately 155,000 women are living with [metastatic breast cancer] in the U.S.-and three in four of these women were initially diagnosed with early-stage breast cancer and later progressed to metastatic breast cancer. The three out of four is a group that was never accurately quantified [before].
"We have very good information on incidence of how many people are initially diagnosed with metastatic breast cancer, and we also have survival information for them from linkages with mortality data. However, our data is patchy and we do not have longitudinal information on recurrence or progression of disease. So we didn't know how many women diagnosed with early-stage breast cancer progressed to metastatic disease and were alive today. Using the methods in the paper, we estimated that they represent approximately 75 percent of all those living with [metastatic breast cancer].
"Ideally, in the future, we would like to collect data on recurrences to have better information on these undocumented population of cancer patients."
2 How were you able to quantify this group of patients living with metastatic breast now- including the women initially diagnosed with an earlier-stage cancer?
"We looked at data from cases initially diagnosed with [metastatic breast cancer] from the SEER registries. We also looked at published data from an MD Anderson study that reported survival from recurrence [metastatic breast cancer] to be lower than survival of women diagnosed with de novo (at diagnosis) [metastatic breast cancer]. The information was used to adjust our survival estimates.
"Then we used U.S. breast cancer mortality data. The method is called 'back calculation' and is often used to estimate an event in the past using information about an event in the future-for example, to estimate the number of HIV infections from the number of AIDS diagnosed cases. In our case, we assumed that each breast cancer death transitioned through [metastatic breast cancer]."
3 What would you say is the takeaway message about these data and the treatment and care of women living with metastatic breast cancer?
"That survival for women initially diagnosed with [metastatic breast cancer] has been improving. Showing the increasing burden of [metastatic breast cancer], we hope to highlight the importance of documenting recurrence to foster more research into the specific needs of this understudied population.
"This study is part of a larger effort at NCI, trying to develop more automated processes and methods to collect recurrence data-possibly using electronic documents, such as claims data, pathology reports, lab tests, and imaging results to point to cancer's return. These data may provide better information on prevention of recurrence."