New Research Shows Breast Cancer Death Rates Have Fallen 58% Due to Better Treatments, Screening

Breast cancer death rates have declined substantially in recent decades, and women are living longer after the diagnosis. What’s behind this change, though? Is it due to screening, treatment advances, better options for patients with metastatic disease? According to a new study, it’s all three.

Research recently published in the Journal of the American Medical Association investigated the reasons why breast cancer death rates in the United States have fallen so sharply, from 48 deaths per 100,000 women in 1975 to 27 per 100,000 in 2019. Using observational and clinical trial data along with models created from algorithms, the researchers studied how the presence and effects of screening and treatments impacted breast cancer mortality rates.

Dr. Jennifer Caswell-Jin, co-first author and assistant professor of medicine at Stanford, says, “We’ve known that deaths from breast cancer have been decreasing over the past several decades, but it’s been difficult or impossible to quantify which of our interventions have been most successful, and to what extent. This type of study allows us to see which of our efforts are having the most impact and where we still need to improve.”

When it comes to improvements to treatment and screening, the team found they were linked with a 58% reduction in mortality since 1975. Of this, roughly 47% was due to better treatments for stage I to III breast cancer, 25% was due to screening, and 29% was due to metastatic cancer treatment options.

This builds on two prior papers from the Cancer Intervention and Surveillance Modeling Network, or CISNET, which was established by the National Cancer Institute to understand how surveillance, screening, and treatment impact breast cancer case rates and mortality. The prior papers had found benefits from mammograms and advances in earlier breast cancer treatment, but this was the first to include metastatic breast cancer. This paper shows that, between 2000 and 2019, the median survival time after metastatic recurrence increased from 1.9 years to 3.2 years.

Dr. Caswell-Jin says, “Initially, we assumed that treatment of advanced disease was unlikely to make a significant contribution to the declines in mortality we documented in the previous two papers. But our treatments have improved, and it’s clear that they are having a significant impact on annual mortality.”

There was also found to be a 2.5-year increase in median survival time for estrogen receptor-positive and HER2-positive patients, as well as a 1.6-year increase for estrogen receptor-positive and HER2-negative patients. However, for patients who were negative for both, the survival time only went up six months.

The researchers say there’s more work to be done, especially as metastatic breast cancer still cannot be cured.

However, Dr. Caswell-Jin says, “But it is rewarding to see that advances have made a difference in these numbers. Our scientific and clinical work is helping our patients live longer, and I believe deaths from breast cancer will continue to steadily decline as innovation continues to grow.”