insulin--isophane and Breast-Neoplasms

To assess whether initiation of insulin glargine (glargine), compared with initiation of NPH or insulin detemir (detemir), was associated with an increased risk of breast cancer in women with diabetes.. This was a retrospective new-user cohort study of female Medicare beneficiaries aged ≥65 years initiating glargine (203,159), detemir (67,012), or NPH (47,388) from September 2006 to September 2015, with follow-up through May 2017. Weighted Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% CIs for incidence of breast cancer according to ever use, cumulative duration of use, cumulative dose of insulin, length of follow-up time, and a combination of dose and length of follow-up time.. Ever use of glargine was not associated with an increased risk of breast cancer compared with NPH (HR 0.97; 95% CI 0.88-1.06) or detemir (HR 0.98; 95% CI 0.92-1.05). No increased risk was seen with glargine use compared with either NPH or detemir by duration of insulin use, length of follow-up, or cumulative dose of insulin. No increased risk of breast cancer was observed in medium- or high-dose glargine users compared with low-dose users.. Overall, glargine use was not associated with an increased risk of breast cancer compared with NPH or detemir in female Medicare beneficiaries.

Topics: Age Factors; Age of Onset; Aged; Aged, 80 and over; Breast Neoplasms; Cohort Studies; Diabetes Mellitus, Type 2; Female; Humans; Hypoglycemic Agents; Incidence; Insulin Detemir; Insulin Glargine; Insulin, Isophane; Medicare; Retrospective Studies; United States

Purpose The association between long-acting insulin analogs and increased breast cancer risk is uncertain, particularly with the short follow-up in previous studies. We assessed this risk long term in women with type 2 diabetes. Methods A population-based cohort of women 40 years or older, all of whom were treated with long-acting (glargine, detemir) or neutral protamine Hagedorn (NPH) insulin between 2002 and 2012, was formed using the United Kingdom's Clinical Practice Research Datalink. Women were followed until February 2015 or breast cancer diagnosis. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) and 95% CIs of incident breast cancer, comparing long-acting insulin analogs with NPH overall, as well as by duration and cumulative dose. Results The cohort included 22,395 women who received insulin treatment, with 321 incident breast cancer events occurring during up to 12 years of follow-up (incidence rate 3.3 per 1,000 person-years). Compared with NPH insulin, insulin glargine was associated with an increased risk of breast cancer (HR, 1.44; 95% CI, 1.11 to 1.85), mainly increasing 5 years after glargine initiation (HR, 2.23; 95% CI, 1.32 to 3.77) and after > 30 prescriptions (HR, 2.29; 95% CI, 1.26 to 4.16). The risk was particularly elevated among prior insulin users (HR, 1.53; 95% CI, 1.10 to 2.12) but not for new users, which included fewer patients and for which one cannot rule out an HR of 1.81. The risk associated with insulin detemir was not significantly elevated (HR, 1.17; 95% CI, 0.77 to 1.77). Conclusion Long-term use of insulin glargine is associated with an increased risk of breast cancer in women with type 2 diabetes. The risk associated with insulin detemir remains uncertain because there are fewer users of this insulin.

Topics: Aged; Breast Neoplasms; Canada; Diabetes Mellitus, Type 2; Female; Humans; Hypoglycemic Agents; Incidence; Insulin Detemir; Insulin Glargine; Insulin, Isophane; Middle Aged; Risk