(CTN News) – Researchers have pinpointed exactly why breast cancer deaths declined by 58% between 1975 and 2019. In the Journal of the American Medical Association, researchers concluded that medical technology has saved lives.
Researchers found that three-quarters of breast cancer deaths can be attributed to better treatment for early-stage and advanced cancers, while the rest can be attributed to routine screenings.
About 29% of breast cancer deaths have been reduced due to better treatment of advanced cancers that have spread elsewhere.
In spite of advanced breast cancer that cannot be cured, women live longer than ever.
This discovery was particularly satisfying to them.
A news release quoted co-lead researcher Dr. Jennifer Caswell-Jin, an assistant professor of medicine at Stanford University, as saying that the declines in death rates we documented in the previous two papers were unlikely to be significantly attributed to treatment of advanced disease.
In spite of this, she said, “our treatments have improved, and they are clearly having a significant impact on the death rate.”
A national consortium of researchers called the Cancer Intervention and Surveillance Modeling Network (CISNET) collaborated on the new study.
Between 1975 and 2000, CISNET researchers estimated that screening mammography contributed to 65% of breast cancer deaths.
In a press release, Sylvia Plevritis, co-senior researcher at Stanford University and chair of biomedical data science, said routine mammogram screening actually reduced Breast Cancer Deaths mortality twenty years ago.
CISNET researchers discovered that some early-stage breast cancer types responded better to treatment, which also affected mortality.
The decline in annual deaths is largely attributable to improved treatment of early-stage breast cancer based on the molecular profile of each cancer, according to Plevritis.
In the current study, researchers explicitly included patients with advanced breast cancer in their models for the first time.
Data from 1975 to 2019 were analyzed using four computer models by CISNET researchers.
The impact of screening mammography, early-stage breast cancer treatment, and advanced breast cancer treatment was remarkably similar across all four studies.
Improvements in early-stage breast cancer treatment account for 47% of the overall reduction, 29% for advanced cancer that has spread, and 25% for mammography screening.
A better survival rate after advanced breast cancer can be measured by the average survival time.
Breast cancer patients in 2000 lived on average 1.9 years, but those in 2019 lived 3.2 years.
Breast Cancer Deaths types vary in survival time:
Between 2000 and 2019, patients with ER-positive and HER2-positive cancers experienced an average survival time increase of 2.5 years.
Women with cancers that were estrogen receptor-positive and HER2-negative lived an average of 1.6 years longer than those with cancers that were not.
Without estrogen receptors or HER2, cancer patients had an average survival advantage of 0.5 years.
“As a breast oncologist, it was meaningful to see real progress over the decades,” Caswell-Jin said. “We still have a lot of work to do; metastatic breast cancer isn’t cured yet. Still, it’s nice to see that advances have made a difference.”