CEACAM5 and lung cancer: As a broad-spectrum tumor biomarker, CEA is elevated in 70% of CRC, 55% of pancreatic cancer, 50% of gastric cancer, 45% of lung cancer, 40% of breast cancer, 40% of urethral carcinoma, and 25% of ovarian cancer patients.149,158,159 Serum CEA levels are proportional to tumor burden.