Main characteristics of eligible studies.

<p>OSCC: oral squamous cell carcinoma; SCC: squamous cell carcinoma of skin; BCC: basal cell carcinoma of skin; SCCNH: squamous cell carcinoma of the head and neck; LHSCC: larynx and hypopharynx squamous cell carcinoma; ALL: acute lymphoblastic leukemia AML: acute myeloid leukemia PB: population-based; HB: hospital-based Phwe: Hardy-Winberg equilibrium; PB*: not defined; Phwe*<0.05 ASMLDR: allele-specific multiple ligase detection reactions; T-ARMS-PCR: Tetra-amplification refractory mutation system–polymerase chain reaction; PCR-RFLP: Polymerase chain reaction-restriction fragment length polymorphism