Aspirin use is not associated with the risk or prognosis of bladder cancer: a case‐control study and meta-analytic assessment

Background Aspirin, widely used for the prevention of cardiovascular disease, could reduce the risk of many types of cancer, including colorectal, breast, and pancreatic cancer. Concerns have also been linked to bladder cancer(BCa), but relevant studies on the effects of aspirin on the occurrence or prognosis of BCa are inconsistent or even controversial. Meanwhile, existing studies focusing on Chinese populations are relatively uncommon, especially for Northeast China. Therefore, this study aims to assess the association of aspirin use with the occurrence and prognosis of BCa in Northeast China. Methods First, we investigated the association between aspirin use and BCa risk in a retrospective cohort study including 1087 patients with BCa from 2002 to 2019 and 1100 healthy persons in the same period as controls. Subsequently, we quantificationally combined the results with those from the published literature evaluating aspirin intake and its effects on the occurrence and prognosis of BCa by meta-analysis after searching the PubMed, Embase, Cochrane Library, and Google Scholar databases up to March 1, 2020. Results The results of our case-control study demonstrated that the regular use of aspirin was not associated with a reduced incidence of BCa (OR = 1.17, p = 0.311). Stratified analyses of sex showed that aspirin intake did not lead to a lower risk of BCa in male patients (OR = 1.25, p = 0.230) or in female patients (OR = 0.90, p = 0.744). Significant correlations were not found in the age subgroup analysis dividing age into younger or greater than 65, with a pooled OR estimate of 1.25 (p = 0.230) and 0.899 (p = 0.744). In 230 patients who relapsed from the 1087 BCa patients above, no significant relationship was found in the aspirin group (RR = 1.19, p = 0.360), and the sex stratification resulted in the same conclusion; however, in people younger than 68, aspirin seemed to have protective effects (RR = 0.60, p = 0.030). In addition, we performed a meta-analysis after searching several databases, and 10 articles involving 12441 BCa cases met the eligibility criteria, contributing to the analysis of aspirin intake and the incidence of BCa. The combined results indicated that aspirin intake was not associated with the occurrence of BCa (OR = 1.03, p = 0.221). In the subgroup analysis, aspirin intake did not reduce the risk of BCa in male patients (OR = 1.08, p = 0.163), female patients (OR = 0.92, p = 0.441), Asian patients (OR = 1.07; p = 0.088), European patients (OR = 1.12, p = 0.390), or North American patients (OR = 0.99, p = 0.839). At the same time, the study type did not influence the lack of a connection between aspirin intake and the risk of BCa in the cohort study (OR = 1.05; p = 0.176) and case-control study (OR = 1.01; p = 0.797). To explore the impact of aspirin intake on the prognosis of patents with BCa, 8 articles involving 3250 BCa cases were eligible. The combined results showed that patients with aspirin intake did not have a significantly lower risk of BCa recurrence than those without aspirin intake (HR = 0.94, p = 0.718), and a consistent conclusion was also reached for overall survival (HR = 1.04, p = 0.879) and cancer-specific survival (HR = 0.98, p = 0.980) by subgroup analysis. Conclusions Both our retrospective study and literature meta-analysis suggested a lack of a relevant association between the use of aspirin and the risk and prognosis of BCa. Thus, additional long-term follow-up prospective research is warranted to clarify the association of aspirin with BCa incidence and prognosis.