The overall survival of breast cancer patients without adjuvant therapy Abstract Purpose There are little data regarding the overall survival (OS) of patients without adjuvant systemic therapy, because most patients have been subject to standardized systemic therapies. We evaluated the baseline risk to facilitate making decisions about adjuvant therapy. Patients and methods A total of 1835 breast cancer patients who did not receive adjuvant systemic therapy between 1964 and 1992 were retrospectively evaluated. We investigated the 10-year disease-free survival (DFS) and OS according to the number of metastatic lymph nodes, pathological T classification, stage, and estrogen receptor (ER) status. Results Survival curves showed that as the number of metastatic lymph nodes, pathological T classification, and staging increased, the 10-year OS and DFS decreased. In univariate and multivariable analyses, the number of metastatic lymph nodes was significantly associated with the DFS and OS, while in a univariate analysis, the pathological T classification and stage were significantly associated with the DFS and OS. ER positivity was a good prognostic factor for the 5-year DFS. However, between 6 and 7 years after surgery, ER negativity was a better prognostic factor than ER positivity. Conclusion We showed survival rates of patients without adjuvant therapy according to TNM classification and ER status. This information can aid in treatment selection for doctors and patients through a shared decision-making approach.