The differential metabolites of ESLC vs. HC were mainly involved in aminoacyl-tRNA biosynthesis; valine, leucine, and isoleucine biosynthesis; ABC transporters; and sphingolipid signaling pathway (p < 0.01); those of NESLC vs. HC were involved in caffeine metabolism; valine, leucine, and isoleucine biosynthesis; aminoacyl-tRNA biosynthesis; Fc gamma R-mediated phagocytosis; and choline metabolism in cancer (p < 0.01). Here, ABCG2 is linked to cancer.