Poorly controlled diabetes increases the risk of metastases and castration-resistant prostate cancer in men undergoing radical prostatectomy: Results from the SEARCH database

Background Although diabetes is inversely related to prostate cancer (PC) risk, to the authors' knowledge the impact of glycemic control on PC progression is unknown. In the current study, the authors tested the association between hemoglobin A1c (HbA1c) and long-term PC outcomes among diabetic men undergoing radical prostatectomy (RP). Methods The authors retrospectively reviewed data regarding men undergoing RP from 2000 to 2017 at 8 Veterans Affairs hospitals. Diabetic patients were identified using International Classification of Diseases, Ninth Revision (ICD-9) codes (250.x) or by an HbA1c value >6.5% at any time before RP. Cox models tested the association between HbA1c and biochemical disease recurrence (BCR), castration-resistant PC (CRPC), metastases, PC-specific mortality, and all-cause mortality. The model for BCR was adjusted for multiple variables. Due to limited events, models for long-term outcomes were adjusted for biopsy grade and prostate-specific antigen only. Results A total of 1409 men comprised the study population. Of these, 699 patients (50%) had an HbA1c value <6.5%, 631 (45%) had an HbA1c value of 6.5% to 7.9%, and 79 (6%) had an HbA1c value >= 8.0%. Men with an HbA1c value >= 8.0% were younger (P < .001) and more likely to be black (P = .013). The median follow-up after RP was 6.8 years (interquartile range, 3.7-10.6 years). On multivariable analysis, HbA1c was not found to be associated with BCR. However, a higher HbA1c value was associated with metastasis (hazard ratio [HR], 1.21; 95% CI, 1.02-1.44 [P = .031]) and CRPC (HR, 1.27; 95% CI, 1.03-1.56 [P = .023]). Although not statistically significant, there were trends between higher HbA1c and risk of PC-specific mortality (HR, 1.24; 95% CI, 0.99-1.56 [P = .067]) and all-cause mortality (HR, 1.09; 95% CI, 0.99-1.19 [P = .058]). Conclusions Among diabetic men undergoing RP, a higher HbA1c value was associated with metastases and CRPC. If validated in larger studies with longer follow-up, future research should test whether better glycemic control improves long-term PC outcomes.