The risk of bias was assessed using the OHAT tool. From 11,838 initially identified records, six studies met the inclusion criteria based on PICO criteria requiring direct investigation of C3a/C5a in human NSCLC contexts. The evidence strongly and consistently points to a critical pro-tumoral role for the C5a/C5aR1 axis. The gene discussed is C3; the disease is non-small cell lung carcinoma.