Head and neck cancer (HNC) is a growing disease, affecting more than 700.000 cases per year and ranking as the sixth most prevalent type of cancer worldwide. The impossibility of properly entering into apoptosis directly influences uncontrolled growth and consequently tumor development and progression. Bcl-2 emerged as a key regulator in the balance between cell apoptosis and proliferation in apoptosis machinery. This systematic review and meta-analysis aimed to review all published studies investigating changes in Bcl-2 protein expression assessed by immunohistochemistry (IHC) and related to prognostic and survival values of patients with HNC. After applying the inclusion and exclusion factors, we reached the number of 20 articles included in the meta-analysis. The random-effect pooled HR (CI95%) value of OS related to Bcl-2 IHC expression in tissues from HNC patients was 1.80 (CI95% 1.21-2.67) (p 0.0001) and DFS was 1.90 (CI95% 1.26-2.86 (p 0.0001). The OS value for the specific oral cavity tumors was 1.89 (1.34-2.67), while in the larynx it was 1.77 (0.62-5.06), and the DFS in the pharynx was 2.02 (1.46-2.79). The univariate and multivariate analyses of OS were respectively 1.43 (1.11-1.86) and 1.88 (1.12-3.16), while in DFS it was 1.70 (0.95-3.03) and 2.08 (1.55-2.80). The OS considering a low cut-off for Bcl-2 positivity was 1.19 (0.60-2.37) and DFS was 1.48 (0.91-2.41), while studies with a high cut-off demonstrated OS of 2.28 (1.47-3.52) and DFS of 2.77 (1.74-4.40). Our meta-analysis demonstrates that Bcl-2 protein overexpression can result in worse LNM, OS, and DFS in patients with HNC, however, it is not a reliable conclusion, due to the wide divergences between the original studies and the fact that many studies have a very high range of confidence and also a high risk of bias.
Keywords: Apoptosis; Bcl-2; Head and Neck Cancer; Survival.
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