BETHESDA, MD — Having Type 2 diabetes mellitus (DM-2) increases mortality risk in breast cancer patients, regardless of whether diabetes was diagnosed before or after breast cancer, according to a recent study.

The report in the journal Cancer Epidemiology, Biomarkers and Prevention notes that most prior studies of breast cancer survival investigated the effect of preexisting DM-2 without assessing the effect when it was diagnosed in relation to breast cancer.1

To expand understanding of the risks, a study team led by researchers from the John P. Murtha Cancer Center at Walter Reed National Military Medical Center analyzed DoD cancer registry and medical claims data from 9,398 women diagnosed with breast cancer between 1998 and 2007.

The analyses indicated that women with DM-2 diagnosed before breast cancer diagnosis tended to have a higher risk of mortality compared with women without diabetes [HR = 1.17; 95% confidence interval (CI), 0.95-1.44] after adjustment for potential confounders.

At the same time, patients diagnosed with DM-2 at or after breast cancer diagnosis had increased mortality compared with women without DM-2 (HR = 1.39; 95% CI, 1.16-1.66). The similar tendency also was observed among most subgroups when results were stratified by race, menopausal status, obesity, tumor hormone receptor status and stage.

“Using data from a health system that provides universal health care to its beneficiaries, this study showed an increased risk of death associated with DM-2, regardless of whether it was diagnosed before or at/after breast cancer diagnosis, study authors concluded, adding, “These results suggest the potential effects of factors independent of the timing of DM-2 clinical diagnosis on the association of DM-2 with overall survival.”

1Shao S, Gill AA, Zahm SH, Jatoi I, Shriver CD, McGlynn KA, Zhu K. Diabetes and Overall Survival among Breast Cancer Patients in the U.S. Military Health System. Cancer Epidemiol Biomarkers Prev. 2018 Jan;27(1):50-57. doi:10.1158/1055-9965.EPI-17-0439. Epub 2017 Nov 2. PubMed PMID: 29097445; PubMed Central PMCID: PMC5808886.