We found that CNVs of C3, C5, C3AR1, and C5AR1 occur in all 33 TCGA cancer types analyzed and at a high frequency in ACC, HNSC, LUSC, KICH, CESC, TGCT, BLCA, READ, ESCA, SARC, OV, UCEC, SKCM, LUAD, and UCS, while CNVs of C3, C5, C3AR1, and C5AR1 occur less frequently in THYM, LAML, THCA, and PRAD. This evidence concerns the gene C5AR1 and cancer.