Modeling neoadjuvant treatment plus additional therapy effects on US population breast cancer mortality

BACKGROUND: Neoadjuvant therapy provides assessment of therapeutic response and the opportunity to guide additional post-surgical adjuvant treatment (NAPAT) for women with residual breast cancer. This treatment approach may reduce breast cancer mortality compared with adjuvant therapy or neoadjuvant treatment without added response-guided therapy (No NAPAT). However, the benefit of this approach has not been quantified in the US population. METHODS: We used six well-established Cancer Intervention and Surveillance Network (CISNET) models to assess the potential impact of NAPAT vs. No NAPAT for women eligible for chemotherapy on breast-cancer mortality from 2018-2030 in the US. We simulated multiple US female birth-cohorts using common screening and treatment inputs derived from clinical trials, large national observational studies and national cancer registries. For years post-2018, we assumed trends in treatments and screening continued as in 2018. Results are presented as a mean and range across models for overall and molecular subtype-specific breast cancer mortality. RESULTS: The models projected that use of neoadjuvant plus additional adjuvant therapy could decrease breast cancer mortality rates to 23.0/100,000 by year 2030 (range across models 20.6-25.4), equaling a 10.5% (6.5%-14.0%) reduction in mortality compared with No NAPAT. Reductions varied by molecular subtype: 30.7% (18.5-38.1%) for women with triple negative tumors, 27.9% (15.6-34.3%) for ER-negative/HER2-positive tumors, 15.4% (10.8-23.6%) for ER-positive/HER2-positive, and essentially no effect 1.3% (-1.0 ̶ 4.0%) for ER-positive/HER2-negative tumors. CONCLUSION: Among women eligible for chemotherapy, use of neoadjuvant plus adjuvant therapy could decrease overall US breast-cancer mortality, even with no further therapeutic advances.