Decreased colorectal atypia among a cohort of gout patients

The relationship between gout and cancer remains uncertain. Some investigators have suggested that uric acid has anti-cancer properties (1, 2). In contrast, other studies have suggested that hyperuricaemia and gout pose an elevated cancer risk (3, 4). To explore the relationship between gout and colorectal lesions in particular, we conducted a crosssectional study of patients in the VA New York Harbor Healthcare System (NYH VA), comparing colorectal cancer and polyp prevalence between gout subjects and a control sample of subjects with osteoarthritis (OA). We identified 1288 patients with an active NYH VA medical record between 1 August 2007 and 31 July 2008 who had a diagnosis of gout (code 274.*) according to the International Classification of Diseases, Ninth Revision (ICD-9). We selected 1288 patients with an ICD-9 code corresponding to OA to serve as controls. Subjects’ medical records were reviewed, and they were considered to have a colorectal lesion if they carried an ICD-9 diagnosis of either colorectal cancer or polyps (153.*, 211.3). Since 299 subjects had concomitant OA, the prevalence of colorectal lesions in this group was additionally compared to that of subjects with gout but without OA. The prevalences of lung (162.*) and prostate (185.*) cancer based on ICD-9 codes were also compared. Colorectal cancer and atypia rates between the gout and OA subjects, as well as other discrete variables, were analysed using the chi-squared and Fisher’s exact tests. Continuous variables such as age were compared using the Student’s t test. All analyses were performed using SPSS version 22.0. This study was approved by the Institutional Review Boards of the NYU School of Medicine and the NYH VA. Subject demographicswere similar across the two groups. Consistent with prior reports (5), gout patients had higher rates of diabetes, chronic kidney disease, and hyperlipidaemia, but similar rates of aspirin/non-steroidal anti-inflammatory drug use. The prevalence of any colorectal atypia (cancer or polyp) was significantly lower among gout subjects than in those with OA (1.8% vs 9.6%, p < 0.01) (Figure 1A). In particular, a diagnosis of polyps was significantly less common among the gout group (0.9 vs 8.4%, p < 0.01). We observed a trend towards a lower prevalence of colorectal cancer diagnosis among gout subjects, which did not reach statistical significance (1.2% vs 1.6%, p = 0.13), possibly because of the relatively small number of diagnoses overall (15 for gout vs 21 for OA), but also possibly because the physician diagnoses of polyp versus cancer were not always pathologically accurate. Among those subjects for whom pathology reports were available, we identified three additional cases of adenocarcinoma in the OA group that had been incorrectly coded by the physician as benign polyps, and two cases of benign polyps in the gout group that had been incorrectly coded as colorectal CA. After correcting for these cases, the difference in colorectal CA prevalence between gout and OA subjects achieved significance (1.0% vs 1.9%, p < 0.001). In contrast, no differences were observed in the prevalences of lung (0.9% vs 1.1%, p = 0.84) or prostate (11.8% vs 12.9%, p = 0.44) cancer between the gout and OA groups. In total, 299 patients in the gout group had concurrent diagnoses of OA. There was no significant difference in physician-reported colorectal cancer (1.0% vs 1.2%, p = 1.0) or polyp (1.0% vs 0.8%, p = 0.72) prevalence between subjects diagnosed with OA and gout, compared to subjectswhowere diagnosedwith gout only (Figure 1B). The reasons for decreased rates of colorectal lesions among gout patients are important to understand, but cannot be ascertained with certainty from the current data. As discussed earlier, it is possible that elevated serum uric acid levels play a protective role. Alternatively, gout itself could protect against colorectal cancer or could be a marker for other protective processes. In vitro studies have suggested that while gout is an inflammatory condition in the acute setting, it may have some anti-inflammatory properties in the quiescent state (6). Our study has a number of important limitations. Since we relied on diagnostic codes in our medical record, we may have excluded diagnoses of colorectal cancer or polyps that were not entered, or were entered incorrectly into subject problem lists. We also did not Letters 81