PURPOSE: Growing breast cancer is associated with an inherent risk of metastasis. If surgical treatment of breast cancer is delayed, the prognosis worsens with increasing tumor size. This justifies the search for a safe time interval between diagnosis and surgery. METHODS: The 2022 population-based data on incidence and the time interval to initial surgery for the United States (U.S.) and Germany are used. Tumor growth and initiation of metastases can be calculated using public data on hormone receptor status, volume doubling time, and tumor size-dependent relative survival. Our assumptions are based on an initial 19.8 mm mean tumor size. 15-year BC-specific mortality in both countries is assumed to be 19.6% without surgical delay. Volume doubling time stratified by hormone receptor status, assumed to be continuous may differ by a factor of 2.4. RESULTS: The U.S. and Germany report 287,850/71,375 new breast cancers for the year 2022 and 2019. If tumor removal is delayed by 8 weeks, mortality rate increases by 2.25/4.79% (HR + /HR-) as estimated by our model. The currently reported mean delay in the U.S. and Germany of 33.7/26.0 days or 4.8/3.7 weeks, respectively, would lead to an estimated 4,676/918 additional BC deaths or a 1.6/1.2% rise in the 15-year BC-specific mortality rate. CONCLUSIONS: This study offers reasonable evidence that confirmed cases of breast cancer should be prioritized and treated according to hormone receptor status and tumor size as soon as possible. Effective screening measures should be followed by timely treatment.