Recent advances in the treatment of metastatic breast cancer have improved population-level survival, according to research presented at the 2022 ASCO Annual Meeting.
Researchers conducted a modeling study to evaluate breast cancer mortality in the United States from 2000 to 2019.
The team found that 19% of the overall reduction in mortality seen in 2019 was attributable to treatments for metastatic breast cancer. The other contributing factors were breast cancer screening and early-stage treatment.
“There has been an accelerating influx of new treatments for breast cancer starting around 1990,” explained study presenter Jennifer Lee Caswell-Jin, MD, of Stanford University in California.
“In general, these treatments are first studied in patients with metastatic breast cancer … and introduced into that setting if they prove efficacious there. Over the next several years, they are then studied in patients with early-stage breast cancer, moving into that setting if they prove efficacious.”
With prior research, Dr Caswell-Jin and colleagues had evaluated the impact of breast cancer screening and treatment of early-stage disease on breast cancer mortality.
For the current study, the researchers focused on the mortality benefit of metastatic treatment. The team used models to simulate US breast cancer mortality from 2000 to 2019.
Results Vary by Subtype
The models suggested that metastatic treatments improved population-level survival in all breast cancer subtypes from 2000 to 2019. However, there was substantial variability by subtype.
Among patients with estrogen receptor (ER)+/HER2- breast cancer, the median survival after distant recurrence increased from 2.0 years in 2000 to 3.5 years in 2019. For those with triple-negative breast cancer, the median survival increased from 1.2 years to 1.8 years.
Among patients with ER+/HER2+ breast cancer, the median survival after distant recurrence increased from 2.3 years in 2000 to 4.8 years in 2019. Among patients with ER-/HER2+ disease, the median survival increased from 2.2 years to 3.9 years.
These numbers translate to a survival improvement of 2.5 years for ER+/HER2+ breast cancer, 1.7 years for ER-/HER2+ breast cancer, 1.5 years for ER+/HER2- breast cancer, and 0.6 years for triple-negative breast cancer.
The researchers also found an estimated 58% reduction in overall breast cancer mortality from all interventions — screening, early-stage treatments, and metastatic treatments.
The greatest reduction in mortality was seen in ER+/HER2+ breast cancer (71%), followed by ER-/HER2+ (61%), ER+/HER2- (59%), and triple-negative breast cancer (40%).
“The steady introduction of new treatments for metastatic breast cancer was essential to the dynamics we observed in our models,” Dr Caswell-Jin said. “We observed a substantial contribution of treatments after metastasis to breast cancer mortality reduction, despite the fact that these treatments generally delay, but rarely prevent, breast cancer death.”
“This sustained contribution, about 20% of overall breast cancer mortality reduction, was maintained by the continual introduction of new treatments for metastatic breast cancer over the past 20 years.”
Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Caswell-Jin JL, Sun L, Munoz D, et al. Contributions of screening, early-stage treatment, and metastatic treatment to breast cancer mortality reduction by molecular subtype in U.S. women, 2000-2017. Presented at ASCO 2022; June 3-7, 2022. Abstract 1008.