In a patient who has just had a molar pregnancy evacuated and has persistently elevated β‑human chorionic gonadotropin (β‑hCG), should the initial imaging for staging be a pelvic ultrasound or a chest X‑ray?

Initial Imaging for Persistent β-hCG After Molar Pregnancy Evacuation

You should perform both pelvic Doppler ultrasound and chest X-ray, but the pelvic ultrasound must come first. 1, 2

Algorithmic Staging Sequence

Step 1: Pelvic Doppler Ultrasound (Mandatory First Study)

The ESMO guidelines explicitly state that pelvic Doppler ultrasound is the initial investigative step when persistent or rising β-hCG is confirmed after molar evacuation 1, 2. This study serves four critical functions:

• Excludes a new pregnancy – You cannot initiate chemotherapy without first ruling out a viable intrauterine gestation, which would be catastrophic if treated as GTN 2, 3
• Quantifies uterine disease burden – Measures uterine size and volume to assess local tumor extent 1, 2
• Maps pelvic spread – Identifies extension of disease within the pelvis for anatomic staging 1, 2
• Provides prognostic information – The Doppler pulsatility index independently predicts resistance to single-agent methotrexate, directly influencing your choice between single-agent versus multi-agent chemotherapy 1, 2

Step 2: Chest X-Ray (Mandatory Second Study)

After the pelvic ultrasound, obtain a chest X-ray because the lungs are the most common metastatic site in GTN 1, 2, 4.

Critical decision point based on chest X-ray findings:

• If chest X-ray is normal → Stop imaging. No further studies are needed 1, 2

  • Although chest CT will detect micrometastases in ~40% of patients with normal chest X-rays, these findings do not alter management or outcomes in low-risk disease 1, 2
  • Do not order CT chest as your initial pulmonary imaging 2

• If chest X-ray shows lesions >1 cm → Immediately escalate to:

  • Brain MRI (or CT if MRI contraindicated) 1, 2, 3
  • CT chest/abdomen/pelvis 1, 2, 3
  • This combination rules out brain and liver metastases, which would dramatically change your therapeutic strategy and risk classification 1, 2

Why This Sequence Matters for Outcomes

The ultrasound-first approach prevents two life-threatening errors:

1. Administering chemotherapy to a viable pregnancy – The ultrasound confirms no new gestation exists before you expose the patient to teratogenic agents 2, 3

2. Missing prognostic information – The Doppler pulsatility index obtained during initial ultrasound helps you select appropriate chemotherapy intensity from the outset, avoiding under-treatment of resistant disease 1, 2

The chest X-ray-before-CT approach prevents unnecessary imaging in the majority of patients while ensuring you detect clinically significant pulmonary metastases that require expanded staging 1, 2.

Common Pitfall to Avoid

Never attempt tissue biopsy of residual uterine tissue to confirm malignant transformation – This carries an extremely high risk of catastrophic hemorrhage and is contraindicated 2, 5. The diagnosis of persistent GTN is made biochemically (rising or plateaued β-hCG) and radiologically, not histologically 1, 4.

Risk Stratification After Complete Staging

Once imaging is complete, apply the FIGO 2000 prognostic scoring system 1, 3:

• Score 0–6 (low-risk) → Single-agent methotrexate or actinomycin D 3, 4
• Score ≥7 (high-risk) → Multi-agent EMA/CO chemotherapy 3, 4

The uterine Doppler findings from your initial ultrasound contribute to predicting which low-risk patients may fail single-agent therapy and require early escalation 1, 2.