COVID-19 Vaccination Caused Increased FDG Uptake During PET Scan in Patient Case

Jian Q. (Michael) Yu, MD, FACNM, FRCPC, chief of nuclear medicine and PET in the Department of Diagnostic Imaging
Jian Q. (Michael) Yu, MD, FACNM, FRCPC, chief of nuclear medicine and PET in the Department of Diagnostic Imaging

PHILADELPHIA (June 9, 2021)—A 70-year-old woman with Hodgkin Lymphoma being treated at Fox Chase Cancer Center had increased FDG uptake in her lymph nodes two days after receiving a COVID-19 vaccination. FDG is short for fluorodeoxyglucose, a radiolabeled sugar used during positron emission tomography (PET) scans.

The follow-up PET scan showed the patient was responding well to cancer treatment, other than increased muscle activity in the deep musculature of the left upper arm and increased activity in several normal-sized left axillary nodes.

The increased activity shown in the scan didn’t indicate tumor growth, but was instead an “artifact,” or misrepresentation in medical imaging, due to a vaccine reaction, said Jian Q. (Michael) Yu, MD, FACNM, FRCPC, chief of nuclear medicine and PET in the Department of Diagnostic Imaging.

Yu said he hopes the findings reassure both patients and referring physicians, and also potentially reduce healthcare costs by avoiding unnecessary imaging tests and biopsies. “These are probably reactive changes from the vaccination,” he said. “You just need to follow up.”

A review of the patient’s history and communication with the referring physician found that she had received her second dose of the Pfizer-BioNTech COVID-19 vaccine in her upper left arm approximately two days before the scan in question. Pain, redness, and swelling at the vaccination site are among the possible side effects of the vaccine, according to the Centers for Disease Control and Prevention. Swollen lymph nodes have also been reported as a possible side effect.

This is not the first time a vaccination has resulted in increased FDG activity in lymph nodes or injection sites. Yu’s article, which included other Fox Chase authors, references other papers that noted similar findings after H1N1 and human papillomavirus vaccinations.

After seeing the Hodgkin Lymphoma patient on a Friday in early February, Yu wrote up the case report and submitted it to the journal Clinical Nuclear Medicine that weekend. The article, “COVID-19 Vaccine-Related Local FDG Uptake,” was published online less than a month later.

“The journal wanted this one really quick,” Yu said. “They wanted to have fresh and up-to-date information, something useful for daily practice.”

Fox Chase Cancer Center (Fox Chase), which includes the Institute for Cancer Research and the American Oncologic Hospital and is a part of Temple Health, is one of the leading comprehensive cancer centers in the United States. Founded in 1904 in Philadelphia as one of the nation’s first cancer hospitals, Fox Chase was also among the first institutions to be designated a National Cancer Institute Comprehensive Cancer Center in 1974. Fox Chase is also one of just 10 members of the Alliance of Dedicated Cancer Centers. Fox Chase researchers have won the highest awards in their fields, including two Nobel Prizes. Fox Chase physicians are also routinely recognized in national rankings, and the Center’s nursing program has received the Magnet recognition for excellence six consecutive times. Today, Fox Chase conducts a broad array of nationally competitive basic, translational, and clinical research, with special programs in cancer prevention, detection, survivorship, and community outreach. It is the policy of Fox Chase Cancer Center that there shall be no exclusion from, or participation in, and no one denied the benefits of, the delivery of quality medical care on the basis of race, ethnicity, religion, sexual orientation, gender, gender identity/expression, disability, age, ancestry, color, national origin, physical ability, level of education, or source of payment.

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