Retrospective evaluation of patients with colorectal cancer (CRC) and type II non-insulin-dependent diabetes (NIDDM).

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507 Background: Patients with NIDDM have an increased risk of colorectal adenomas and CRC possibly mediated through the insulin growth factor receptor pathway. Metformin is associated with anticancer efficacy in preclinical models and a lower risk of cancer mortality in patients with NIDDM. We undertook to evaluate the difference in outcome in NIDDM patients with CRC based upon their medications taken for glycemic control. Methods: We conducted an IRB-approved (DR09-0719) retrospective analysis of 4,758 patients seen at a single institution (University of Texas M. D. Anderson) with CRC between the years of 2005-2008, to determine the prevalence of NIDDM in this patient population, in addition to determining whether patient survival differs based upon their diabetic therapy. Results: 425 out of 4,758 CRC patients (8.9%) were identified as having NIDDM. Gender, male:female 283:142 (67%, 33%), age, mean 62 years (range 31-91), stage I/II/III/IV 37:55:175:158 (8.7%, 12.9%, 41.2%, 37.2%). Overall survival (OS) for the 397 patients with follow-up data available, by univariable Kaplan Meier analysis, was 63.7 months (95% confidence interval (CI), 52.3-75.5). Patients with NIDDM and CRC treated with metformin as one of their diabetic medications had a survival of 76.9 months (95% CI, 61.4-102.4) as compared to 56.9 months in those patients not treated with metformin (95% CI, 44.8- 68.8), p = 0.048. By using a Cox regression model adjusted for age, sex, race, body mass index, and initial stage of disease we demonstrated that NIDDM patients treated with metformin had a 30% improvement in OS when compared to NIDDM patients treated with other diabetic agents. There was a non-statistically significant trend toward higher complete and minor pathologic response rate (≤ 10% residual tumor) in NIDDM patients with rectal cancer receiving chemoradiation who were treated with metformin when compared to those who were not (14/19, 74% vs. 9/19, 47%, p = 0.09). Conclusions: In this analysis the use of metformin in NIDDM patients with CRC was associated with an improved overall survival. While these results are consistent with the findings in other solid tumors they will need to be validated in other colorectal cancer data sets. No significant financial relationships to disclose.