Effect of Diabetes Treatment on Breast Cancer Outcomes: A Systematic Review and Meta-analysis

Joanna-Grace Mayo Manzano, The University of Texas School of Public Health


BACKGROUND: Diabetes and cancer are two leading causes of morbidity and mortality worldwide. Diabetes is a known risk factor for certain kinds of cancer, and diabetes treatment such as Metformin, has also been implicated in influencing cancer-specific outcomes. The role of other diabetes treatment regimens in impacting cancer outcomes has not been extensively studied. METHODS: We conducted a systematic review and meta-analysis to determine the impact of different treatment regimens for diabetes on cancer outcomes among adult patients with breast cancer. We conducted a comprehensive search of relevant studies in MEDLINE, EMBASE, Web of Science, Cochrane, clinicaltrial.gov and Pubmed epubs databases from inception to May 3, 2017. Studies were included if they evaluated the impact of diabetes treatment on cancer outcomes among adult patients who had both breast cancer and diabetes mellitus. We included original research studies only and excluded non-english studies and those that involved animals or cell lines only. The MOOSE guidelines were followed in reporting our findings. Quality of included studies were assessed using the Newcastle Ottawa Scale for observational studies. RESULTS: The primary outcome in this study was overall survival (OS) which was reported in 14 studies. Thirty-two independent studies were included in the qualitative synthesis, and 30 were included in the meta-analysis comprising a cohort of 20,685 patients with breast cancer and diabetes. Types of diabetes treatment evaluated were metformin, thiazolidinediones, insulin, and sulfonylureas whether as monotherapy or in combination. In pooled analysis, patients on metformin had improved OS (reported as risk of death (HR 0.49, 95% CI 0.41, 0.59), breast cancer-specific survival (HR 0.59, 95% CI 0.39, 0.89), and disease free survival (HR 0.46, 95% CI 0.25, 0.84) ) compared to non-metformin users. Metformin was also protective for all-cause mortality when compared to insulin (HR 0.64 95% CI 0.45, 0.91). Patients treated with insulin had worse OS compared to patients who were not on insulin (HR 1.79, 95% CI 1.02, 3.14). CONCLUSIONS: Our findings support previous findings that metformin has treatment benefit in terms of cancer outcomes and this is important when considering this drug as an adjunct to cancer treatment. We further show that compared to other diabetes treatment, metformin appears to have the most benefit in terms of overall survival and cancer-specific outcomes. This is most helpful for the internist or subspecialist when considering different anti-diabetes regimens in a patient with both breast cancer and diabetes.

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Recommended Citation

Manzano, Joanna-Grace Mayo, "Effect of Diabetes Treatment on Breast Cancer Outcomes: A Systematic Review and Meta-analysis" (2018). Texas Medical Center Dissertations (via ProQuest). AAI10928125.