Abstract
BackgroundThe relationship between cancer with overweight and obesity has been extensively reported. However, the association between urinary cancers with these risk factors remains unclear, with existing reports showing conflicting findings. The current review, therefore, sought to clarify the latter association by assessing the methodological and reporting quality of existing systematic reviews on the subject.MethodsWe first screened PubMed, EMBASE, and Cochrane Library databases for relevant literature and subjected the resulting articles to meta-analysis. We adopted the AMSTAR-2 and PRISMA checklists for assessing methodological and reporting quality, respectively, then performed meta-analyses to determine the relationship between incidence and mortality of three types of urinary cancers with obesity and overweight. Indirect comparisons were also done across subgroups.ResultsAll systematic reviews (SRs) were of critically low methodological quality. Seventeen SRs had minimal reporting flaws, and 11 SRs had minor reporting flaws. We found an association between obesity with an incidence of kidney (RR = 1.68, 95% CI 1.47–1.92), bladder (RR = 1.1, 95% CI 1.07–1.13), and prostate (RR = 1.02, 95% CI 0.91, 1.13) cancers. Similarly, overweight was associated with the incidence of the three types of cancer, recording RR values of 1.37 (95% CI 1.26–1.48), 1.07 (95% CI 1.03–1.1), and 1 (95% CI 0.93, 1.07) for kidney, bladder, and prostate cancers, respectively. With regard to the dose analysis, the RR of BMI (per 5 kg/m2 increase) was associated with kidney (RR = 1.24, 95% CI 1.2–1.28), bladder (RR = 1.03, 95% CI 1.02–1.05), and prostate (RR = 1.02, 95% CI 1.01, 1.03) cancers.ConclusionsThis comprehensive quantitative analysis provides an affirmation that overweight and obesity are strong risk factors for kidney cancer, owing to a strong association between them. Conversely, a weak association between overweight and obesity with bladder and prostate cancers confirms their status as mild risk factors for the 2 types of cancer. But due to the low quality of included SRs, the results need to be interpreted with caution.Systematic review registrationPROSPERO CRD42019119459
Highlights
The relationship between cancer with overweight and obesity has been extensively reported
A weak association between overweight and obesity with bladder and prostate cancers confirms their status as mild risk factors for the 2 types of cancer
Mini-abstract This umbrella review assessed the methodological and reporting quality of systematic reviews evaluating the relationship between three types of urinary cancer with obesity and overweight
Summary
The relationship between cancer with overweight and obesity has been extensively reported. According to the Global Cancer Statistics of 2018, published by the World Health Organization/International Agency for Research on Cancer [2], prostate cancer represents the second most common type of cancer and the fifth leading cause of cancer-related deaths in men. This type caused an estimated 1.3 million new cases and 359,000 deaths in 2018 alone, whereas bladder cancer accounted for 549,000 new cases and 20 million deaths worldwide. Previous studies have suggested that cumulative effects of cigarette smoking, alcohol consumption, obesity, and genetic susceptibility may be risk factors for urinary cancer [3, 4]. Accurate understanding of these risk factors is critical for the development of effective approaches for cancer prevention and treatment
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