ReviewAssociation between obesity and bladder cancer recurrence: A meta-analysis
Introduction
Bladder cancer is a common urinary system malignancy with high morbidity and relapse rate. It is the ninth most common and seventh most malignant carcinoma in the world. There are approximately 356,000 new bladder cancer cases and 145,000 bladder cancer deaths annually [1]. Notably, the high incidence of recurrence is a nodus in clinical practice. In accordance with Tumor-Node-Metastasis classification (TNM), tumor grade, and number of primary tumors, 50%–90% of bladder cancer patients will suffer recurrences [2].
Obesity is a public health problem in general and the prevalence of obesity is increasing [3]. As of 2013, the number of overweight and obese individuals reached 2.1 billion worldwide. Of these, the United States accounted for the largest proportion, followed by China and India. Obesity causes a numerous health problems and may impact cancer [4]. In fact, more research has focused on elucidating the relationship between obesity and cancer development. Bhaskaran et al. studied the association between BMI and several cancers and found that high BMI can increase risk of some cancers, like uterine and kidney cancers [5]. Since Kanabrocki et al. first reported the association between obesity and bladder cancer in 1965 [6], numerous studies have tried to identify the effect of obesity on bladder cancer. A meta-analysis by Sun et al. found that obesity increased the risk of bladder cancer and promoted cancer progression [7]. Although several cohort studies have examined the association between obesity and bladder cancer prognosis such as survival and recurrence [[8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18]], results remain largely inconclusive. For example, an epidemiologic study by Kluth et al. found that obesity was an independent risk factor of bladder urothelial carcinoma recurrence. Patients with BMI > 30 kg/m2 had worse outcomes than non-obese individuals [12]. A similar positive association between obesity and increased recurrence rate was also reported by other research teams [9,15,18]. In contrast, a prospective cohort study found that obesity was not an independent risk factor for recurrence [14]. Therefore, we conducted a meta-analysis to summarize the relationship between recurrence, overall survival of bladder cancer and obesity.
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Ethical approval
This article did not contain any studies with human participants or animals performed by any of the authors. Ethics approval was not necessary for this study, as this meta-analysis was based on the published data.
Search strategy
Literature was identified by searching PubMed through November 1, 2017. The key words were as follows: ‘obesity’, ‘body mass index’ (‘BMI’), together with ‘bladder cancer’. The references of identified literature were screened for potentially relative articles.
Inclusion criteria
Studies were available
Study characteristics
We identified 387 articles from PubMed prior to November 1, 2017. A total of eleven articles were included in final meta-analysis [[8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18]]. Four studies conducted in North America [8,10,16,17], five in Europe [9,[12], [13], [14],18] and two in Asia [11,15]. A total of 726 patients were recruited in study by Wyszynski et al., and only data from 338 patients were available for BMI analysis [14]. Study by Maurer et al. recruited a total of
Discussion
Postoperative recurrence is a common occurrence during the clinical treatment of bladder cancer, which has aroused wide attention. Our findings revealed that obesity was associated with increased bladder cancer recurrence risk. Subgroup analyses also demonstrated that female patients had higher recurrence risk compared to male individuals.
Treating recurrent cases as new cancers is already a consensus during clinical therapy [26].Bladder cancer is a fairly common and costly malignancy because of
Funding
This study was partly supported by National Natural Science Foundation of China (81473050), Collaborative Innovation Center For Cancer Personalized Medicine, and the Priority Academic Program Development of Jiangsu Higher Education Institutions (Public Health and Preventive Medicine).
Ethical approval
Compliance with ethical standards.
Conflict of interest
The authors declare that they have no conflict of interest.
Informed consent
For this type of study, informed consent does not apply.
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These authors contribute equally to this work.