What is the role of alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) tumor markers in the diagnosis and management of germ cell tumors?

Tumor Markers in Germ Cell Tumors

AFP and β-HCG are mandatory tumor markers that must be measured in all patients with suspected germ cell tumors for diagnosis, risk stratification, treatment monitoring, and surveillance, while LDH serves as a critical prognostic factor in advanced disease. 1, 2

Mandatory Marker Panel

For both seminoma and non-seminoma, AFP and β-HCG must be measured before any intervention. 1 In advanced disease, LDH must be added to this panel as it functions as an independent prognostic factor. 1, 2

Timing of Measurement

• Pre-orchiectomy: Draw AFP and β-HCG before orchiectomy in all patients with suspected testicular germ cell tumors to establish baseline values and aid diagnosis. 1, 2 Normal marker levels do not exclude testicular cancer and should never delay orchiectomy. 1, 2

• Post-orchiectomy: Repeat markers approximately 7 days after orchiectomy to assess half-life kinetics (AFP half-life: 5-7 days; β-HCG half-life: 1-3 days), then follow serially until normalization or stable plateau. 2, 3 Persistent or rising markers indicate metastatic disease. 2

• Before any subsequent treatment: Measure AFP, β-HCG, and LDH before chemotherapy or retroperitoneal lymph node dissection (RPLND) to stratify risk and select appropriate treatment regimens. 1, 2

Diagnostic Role

Elevated AFP or β-HCG supports the diagnosis of germ cell cancer in young men with retroperitoneal, supraclavicular, or mediastinal masses. 1

• In rare patients with life-threatening metastatic disease and unequivocally elevated AFP or β-HCG, substantially elevated markers may be considered sufficient for diagnosis, and chemotherapy should not be delayed for tissue diagnosis. 1

• Critical distinction: Elevated AFP definitively excludes pure seminoma, as AFP is produced only by nonseminomatous elements (embryonal carcinoma and yolk sac tumor). 2, 4 β-HCG can be mildly elevated in seminoma due to syncytiotrophoblastic giant cells. 2, 4

Risk Stratification Using IGCCCG Classification

The International Germ Cell Cancer Collaborative Group uses marker thresholds to stratify patients into prognostic groups that determine treatment intensity: 2

• S1 (Good prognosis): LDH <1.5× ULN, β-HCG <5,000 IU/L, AFP <1,000 ng/mL 2
• S2 (Intermediate prognosis): LDH 1.5-10× ULN, β-HCG 5,000-50,000 IU/L, AFP 1,000-10,000 ng/mL 2
• S3 (Poor prognosis): LDH >10× ULN, β-HCG >50,000 IU/L, or AFP >10,000 ng/mL 2

Treatment Monitoring

Measure AFP, β-HCG, and LDH before each chemotherapy cycle to assess treatment response. 1, 3 The half-life kinetics during chemotherapy indicate treatment effectiveness. 3, 5

• If tumor marker levels rise between day 1 of cycle 1 and day 1 of cycle 2, repeat assays midway through cycle 2 to determine whether levels have begun to decline. 1

• Normalized markers designate the appropriate phase for discussing surgical indications for residual masses. 3

Critical Interpretation Pitfalls

False Elevations of β-HCG

• Hypogonadism from orchiectomy and chemotherapy can cause false β-HCG elevation; supplemental testosterone can reduce this. 2
• Heterophilic antibodies can cause false-positive hCG results, particularly in women. 1, 2, 6
• Other cancers can produce moderately elevated hCG levels, so elevations are not diagnostic in patients with poorly differentiated cancers of uncertain origin. 1

False Elevations of AFP

• Liver dysfunction from chemotherapy, anesthetics, antiepileptics, viral hepatitis, or alcohol can elevate AFP without tumor progression. 2, 7 These elevations must be interpreted with caution to avoid unnecessary treatments. 7
• Hepatocellular carcinoma and other non-germ cell malignancies can elevate AFP. 2

LDH Limitations

• LDH is highly nonspecific: Strenuous exercise, liver disease, myocardial infarction, kidney disease, hemolysis, and pneumonia can all elevate LDH. 1, 2
• Hemolysis of blood samples falsely elevates LDH, making proper specimen handling critical. 8
• LDH isoenzyme fractionation is not recommended as it adds no clinical value beyond total LDH. 8
• The proven utility of LDH is primarily for prognosis in chemotherapy-naïve patients with metastatic disease. 1, 2

Surveillance After Treatment

Patients on Surveillance (Stage I)

• Clinical review, chest X-ray, and tumor markers monthly for year 1, every 2 months for year 2, every 4 months for year 3, then every 6 months to 5 years. 1
• CT scans at 3,6,9,12, and 24 months. 1

Post-Chemotherapy Patients

• Clinical review, chest X-ray, and tumor markers every 2 months for year 1, every 3 months for year 2, then every 6 months to 5 years, then annually. 1
• CT scans only as clinically indicated. 1
• Marker elevation during surveillance often represents the first sign of treatment failure and indicates recurrence. 3

What NOT to Do

• Never use tumor markers for screening in asymptomatic populations. 1
• Never delay orchiectomy based on normal marker levels, as 23% of non-seminomas have neither AFP nor HCG elevation. 4
• Never use markers alone to guide treatment in cancer of unknown primary with indeterminate histology without considering clinical context. 1
• Never order LDH isoenzymes as they provide no additional clinical utility. 8