Yttrium-90 radiation meant for liver tumors landed in the wrong tissue during treatments at Johns Hopkins Hospital in Baltimore and PeaceHealth Sacred Heart Medical Center in Springfield, Oregon, according to two Nuclear Regulatory Commission event reports, numbers 58497 and 58495. Both were filed by state radiation programs as medical events on Oct. 14, 2026, after the treatments on Oct. 12 and Oct. 13.
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The reports describe a misplaced dose, not a confirmed injury. In the Johns Hopkins case, the licensee estimated that 2 to 2.5 percent of the administered activity refluxed into the area of the left gastric artery, and the patient has been started on a preventive stomach medicine.
Johns Hopkins event 58497 and the left gastric artery
According to the NRC event notification report, the Maryland Department of the Environment’s Radiological Health Program told the commission that the event at Johns Hopkins Hospital occurred at 9:15 a.m. Eastern time on Oct. 12. The prescription was about 60.1 millicuries of yttrium-90 microspheres to treat liver cancer in segments two and three of the liver, with an intended liver dose of 370 gray. Pre-treatment scans showed no significant shunting concern, meaning no sign that blood would carry microspheres elsewhere.
Post-treatment imaging found activity in the left gastric artery and in the fundus and cardia region of the stomach. The licensee’s preliminary dose estimates were about 56 to 93 gray to the fundus and cardia region, about 19 gray to the stomach wall, and 1,390 to 2,800 gray to the wall of the left gastric artery. The patient and the referring physician were notified, the patient was started on a prophylactic proton pump inhibitor, and the state’s evaluation is ongoing.
PeaceHealth event 58495 in Springfield, Oregon
The Oregon event unfolded differently. The Oregon Health Authority’s Radiation Protection Services reported that the prescribed activity was 5.67 gigabecquerels of yttrium-90 microspheres to the right lobe of the liver, for a target dose of 120 gray. The licensee estimated the delivered dose at about 123 gray. A post-treatment scan showed the delivery was segmental to the caudate lobe of the liver and surrounding tissue, and SPECT-CT scans showed activity near the gallbladder fossa even though the patient has no gallbladder.
The authorized user concluded that some activity went to the liver and some to surrounding tissue and ducts. The patient was informed of the findings, and the report does not describe any harm. The notification was made to the commission on Oct. 14 at 1:31 p.m. Eastern time, and the report is listed in Region 4.
Why these cases count as medical events
Under the federal rule at 10 CFR 35.3045, a licensee must tell the commission by the next calendar day after discovery and file a written report within 15 days. The rule also calls for notifying the patient and the referring physician within 24 hours, unless the physician decides otherwise. Dose thresholds and wrong-site criteria determine what qualifies, which is why a small fraction of misdirected activity can trigger a report even when the patient shows no symptoms. Both event reports note that a medical event does not necessarily result in patient harm.
Misplaced microspheres are not new to regulators. An Idaho National Laboratory review prepared for the commission, covering fiscal years 2008 to 2017, counted 152 reportable Y-90 microsphere events involving 157 patients, 21 of them classified as wrong treatment site. Human error was the leading cause, at 51 events, followed by equipment failure at 38. The authors cautioned that the data were not normalized for the number of treatments performed.
How radioembolization can miss its target
Radioembolization works by delivering radioactive glass or resin microspheres through the artery that feeds a liver tumor. Mapping before treatment is standard, but it can miss small vessels. A published case report in Nuclear Medicine and Molecular Imaging described a gastric ulcer after Y-90 therapy despite negative pre-procedural imaging, traced to a tiny accessory artery running from the left hepatic artery to the stomach. The authors recommended post-treatment SPECT-CT to confirm where the microspheres went, and noted that gastric ulceration is rare.
The commission’s own medical advisers have debated how to define these events. A 2014 report from the commission’s Advisory Committee on the Medical Uses of Isotopes recommended that irradiation of the stomach and lungs be treated as a known risk, because final microsphere distribution depends on each patient’s vascular anatomy and blood flow. The current reports show the commission still requires states and licensees to report such deviations, and the Maryland review of the Johns Hopkins case remains open. A written report on the Oregon event is due to the commission within 15 days of discovery, so further detail on both cases may follow.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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