Diabetes mellitus without metformin intake is associated with worse oncologic outcomes after radical nephroureterectomy for upper tract urothelial carcinoma

Aims Evidence suggests a detrimental effect of diabetes mellitus (DM) on cancer incidence and outcomes. To date, the effect of DM and its treatment on prognosis in upper tract urothelial carcinoma (UTUC) remains uninvestigated. We tested the hypothesis that DM and metformin use impact oncologic outcomes of patients treated with radical nephroureterectomy (RNU) for UTUC. Methods Retrospective analysis of 2492 patients with UTUC treated at 23 institutions with RNU without neoadjuvant therapy. Cox regression models addressed the association of DM and metformin use with disease recurrence, cancer-specific mortality and any-cause mortality. Results A total of 365 (14.3%) patients had DM and 194 (7.8%) patients used metformin. Within a median follow-up of 36 months, 663 (26.6%) patients experienced disease recurrence, 545 patients (21.9%) died of UTUC and 884 (35.5%) patients died from any cause. Diabetic patients who did not use metformin were at significantly higher risk of disease recurrence and cancer-specific death compared to non-diabetic patients and diabetic patients who used metformin. In multivariable Cox regression analyses, DM treated without metformin was associated with worse recurrence-free survival (HR: 1.44, 95% CI 1.10-1.90, p = 0.009) and cancer-specific mortality (HR: 1.49, 95% CI 1.11-2.00, p = 0.008). Conclusions Diabetic UTUC patients without metformin use have significantly worse oncologic outcomes than diabetics who used metformin and non-diabetics. The possible mechanism behind the impact of DM on UTUC biology and the potentially protective effect of metformin need further elucidation.