INS and breast cancer: However, patients in the third tertiles of dose–response parameters might show a significantly higher risk of breast cancer while compared to never-users: 1.185 (1.026-1.368), 1.260 (1.096-1.450) and 1.257 (1.094-1.446) for ≥67 months for time since starting insulin, ≥39,000 units for cumulative dose of insulin, and ≥21.8 months for cumulative duration of insulin, respectively.