A Randomized, Pragmatic, Adaptive Trial of Metformin for Glucose Intolerance or Increased Body Mass Index in Prostate Cancer Patients

Summary

Metformin is used widely in the treatment of type 2 diabetes. It has off-label indications for use in the prevention of diabetes and in hyperinsulinar obesity. In medical practices, the implementation of metformin for these off-label indications is variable, often at the level of the provider. Multiple retrospective investigations have also shown a clinical benefit in men with prostate cancer who are incidentally treated with metformin. This pragmatic study will test the feasibility of enrolling patients who have glucose intolerance (as defined by HbA1c of 5.7-6.4%) and/or who have increased BMI (BMI greater than or equal to 25 kg/m2) to a randomized pragmatic study of metformin plus lifestyle modification information versus lifestyle modification information only. For purposes of the scope of this project and the study's feasibility, this will be implemented in a group of prostate cancer patients, who may have additional benefits from metformin.

Detailed description

In this study, subjects with prostate cancer will be randomized to metformin plus educational material for lifestyle modification versus educational material for lifestyle modification alone and followed for up to 10 years. Population-based, retrospective studies have reported improved outcomes, including prostate cancer specific mortality, with the incidental use of metformin in prostate cancer patients. One prominent study is this area from Margel, et al was published in 2013.2 Using the administrative database from several Ontario health districts, men aged 66 with incidental diabetes and prostate cancer antigen (PCA) were studied. The study included over 3000 men and found an adjusted hazard ratio of 0.76 (95% CI, 0.64 to 0.89) for PCA-specific mortality for each additional 6 months of metformin use. There was no relationship to survival with any other diabetic medication. In addition to the use of metformin for the prevention of metabolic complications related to obesity and the prevention of diabetes, there are several studies reporting a potential benefit in those with prostate cancer. In a Veterans Administration-based study, more than 87,000 subjects were identified with PCA in the sample.3 The subjects were analyzed in 3 cohorts: 1) no diabetic medication (DM), 2) DM without metformin use and 3) DM with metformin use. Men with DM who were treated with metformin were found to have improved OS (HR 0.82, 95% CI 0.78 - 0.86, for mortality) compared to men with DM not on metformin. Reduced cancer specific mortality was also observed in the men with DM on metformin (HR 0.70, 95% CI 0.64 -0.77) in comparison to men with DM not taking metformin (HR 0.93, 95% CI 0.85 -1.00) - the reference group were those without DM. Despite considerable interest in these findings, there is little if any prospective data on the use of metformin in this setting.

Arms & interventions

• DrugMetformin

  Metformin is a medication used to treat type 2 diabetes, gestational diabetes, and prediabetes. In this study, patients on the Metformin arm will be started on 850 mg daily for 2 weeks, then escalated to a final dose of 850 mg twice daily, which is lower than the maximum recommended dose of 2550 mg total daily.

• BehavioralLifestyle Modification

  Patients randomized to this arm will receive standard lifestyle modification recommendations. This will include the general recommendation to increase exercise level mildly, after discussing with the medical provider. There is a potential low-level risk in increasing one's exercise levels. Here are some examples of the educational material from the American Diabetes Association website, and topics will be rotated on quarterly basis: Healthy eating: https://www.diabetes.org/nutrition/healthy-food-choices-made-easy Prediabetes: https://www.diabetes.org/diabetes-risk/prediabetes Fitness: https://www.diabetes.org/fitness/get-and-stay-fit Weight loss: https://www.diabetes.org/fitness/weight-loss

Outcome measures

Eligibility criteria