Radiopharmaceutical extravasation

Extravasation is the inadvertent leakage of an injected radiopharmaceutical into the tissue surrounding the injection site instead of the vein. For diagnostic tracers labelled with 99mTc, 123I, 18F or 68Ga, extravasation is common but rarely causes tissue injury; a systematic review of more than 3,000 reported diagnostic extravasations found fewer than 0.1% caused symptoms requiring clinical follow-up, and none of the 99mTc/123I/18F/68Ga cases needed intervention. Its main practical consequence for diagnostics is degraded image quantification (altered biodistribution and reduced injected activity reaching the target), which matters most for quantitative studies such as dosimetry or lymphoscintigraphy.

Extravasation of a therapeutic radiopharmaceutical is potentially more serious because the higher administered activity and longer-range or higher-LET emissions can cause localised soft-tissue injury, including skin necrosis in severe cases. SNMMI guidance instructs staff to stop the infusion immediately if resistance is felt, swelling appears, or the patient reports pain, and to document the estimated infiltrated volume and site. Symptoms warranting evaluation by a plastic surgeon include swelling greater than 2.5 cm, numbness, blanched or translucent skin, tight or leaking skin, discoloration or bruising, and any circulatory or nerve impairment. Management strategies described in the literature (cooling versus warming, elevation, and rarely surgical excision) are not strongly evidence-based, and EANM/SNMMI procedure guidelines give only limited practical advice, largely confined to the 90Y-ibritumomab tiuxetan (Zevalin) guideline, which recommends local hyperthermia, elevation and gentle massage.

Under US NRC policy, extravasations have historically been treated as a practice-of-medicine issue rather than a reportable medical event, since they occur even with technically correct injections; however, an extravasation that leads to unintended permanent functional damage can be reportable as a medical event under 10 CFR 35.3045(b), and SNMMI and the NRC's Advisory Committee on the Medical Uses of Isotopes have discussed whether CTCAE grade 3-4 tissue injury from a therapeutic extravasation should trigger notification requirements similar to other medical events.