Association between serum amyloid A levels and cancers: a systematic review and meta-analysis

Objective Increased serum amyloid A (SAA) levels have been investigated in various human malignancies, but a consistent perspective has not been established to date. This study systematically reviewed the association between SAA levels and cancers. Methods Cochrane Library, PubMed and Embase were carefully searched for available studies. The following keywords were used in database searches: serum amyloid A', SAA', cancer', tumour', carcinoma', nubble', knurl' and lump'. Pooled standard mean differences (SMDs) with corresponding 95% CIs were calculated using random-effects model analysis. Results Twenty studies, which contained 3682 cancer cases and 2424 healthy controls, were identified in this systematic review and meta-analysis. Our study suggested that the average SAA concentrations in the case groups were significantly higher than those in control groups (SMD 0.77, 95% CI 0.55 to 1.00, p<0.001). Subgroup analysis revealed that continent, age and cancer location were associated with SAA level differences between case groups and control groups. Sensitivity analyses showed the robustness and credibility of our results. In addition, we further stratified analyses for cancer stages and found that the concentrations of SAA increased gradually with the aggravation of cancer stages. Conclusion High circulating SAA levels were markedly associated with the developing risks of cancer, especially for participants from Asia, Oceania and Europe, or subject age more than 50, or locations in oesophageal squamous cell, ovarian, breast, lung, renal and gastric cancers. In addition, our study found that the concentrations of SAA increased with the severity of cancer stages.