History of Diabetes and Survival Outcome Among Participants 65 Years or Older in SWOG Clinical Trials.

PURPOSE

Diabetes is common, increases with age, and may affect outcomes among people with cancer. Understanding the association between diabetes and cancer outcome is challenging, because patients with diabetes have increased all-cause mortality compared with patients without diabetes.

METHODS

We systematically examined the phase III trial database of SWOG to identify patients enrolled in trials during the period from 1999 to 2011. We linked the SWOG clinical records to Medicare claims data according to Social Security number, sex, and date of birth. Medicare claims were used to identify diabetes with at least 6 months of continuous Medicare coverage immediately before registration. Multivariable Cox regression was used to compare survival outcomes between patients with and without diabetes for each of 10 tumor cohorts. The primary outcome was overall survival. We also examined progression-free survival and cancer-free survival.

RESULTS

In total, 6,422 patients from 15 trials were ≥ 65.5 years of age, of whom 3,173 patients (49%) met the criteria for linkage to Medicare claims. Thirty percent (n = 952) had claims for diabetes before registration. Patients with diabetes were more likely to be black ( P < .001), but no other differences in demographic characteristics were observed. In multivariable Cox regression, no association was found between baseline diabetes and overall or progression-free survival; in one case, patients with diabetes had marginally worse cancer-free survival (advanced non-small-cell lung cancer; P = .05). A global test found that baseline diabetes was associated with worse overall survival ( P = .03) across the entire panel of analyses.

CONCLUSION

Diabetes is common among elderly patients enrolled in clinical trials. Unlike prior observational studies, among patients treated with uniform treatment regimens, and controlling for known prognostic factors, we did not observe an association between diabetes and progression-free or cancer-free survival.