Percutaneous Intralesional Therapeutic Agent Injection

Background and indications

Image-guided percutaneous intralesional injection consists of directly injecting a therapeutic agent into a tumoral or cystic lesion. Agents include: ethanol (ablation of HCC, thyroid/renal/hepatic cysts), methotrexate (ectopic pregnancy), corticosteroids (inflammatory pseudotumor, sarcoidosis), or intratumoral immunotherapy agents (T-VEC for melanoma, BCG for certain tumors).

For HCC, percutaneous ethanol injection (PEI) was the first curative percutaneous treatment, effective for tumors ≤ 2 cm, although largely superseded by RFA/MWA.

Pre-procedure assessment

Assessment depends on indication: lesion imaging (CT/MRI/ultrasound), appropriate blood panel, and tumor board discussion when applicable. Percutaneous access feasibility is evaluated.

Procedure

Under local anesthesia (± sedation) and ultrasound or CT guidance, a fine needle (20-22G) is inserted into the lesion. The therapeutic agent is slowly injected under real-time control. For HCC ethanol ablation, 2-10 mL of 95% ethanol is injected per session. Multiple sessions may be needed. The procedure takes 15-30 minutes.

Results and scientific evidence

For HCC ≤ 2 cm, percutaneous ethanol injection offers 80-90% complete necrosis rate and 50-60% 5-year survival. Ethanol remains useful as a complement to thermal ablation for small tumor residues or locations inaccessible to RFA/MWA.

Risks and complications

Local pain (30-50%, transient), fever (5-10%), hemorrhage (< 2%), tumor tract seeding (exceptional with fine needles). Major complications are rare (< 2%).

Recovery

Same-day discharge or 1 night hospitalization depending on injected volume and location. Control imaging at 1 month.

Practical information

The procedure is performed as an outpatient or short inpatient stay depending on the case. It is performed by an interventional radiologist.