PET imaging shows how COVID vaccines confuse cancer detection
Researchers at the Mayo Clinic in Rochester, Minnesota compared PET scans of patients before and after receiving Pfizer-BioNTech or Moderna COVID-19 vaccinations and observed increased absorption of FDG and carbon- 11 (C-11) choline by axillary and ipsilateral lymph nodes. deltoids. There was no axillary lymph node uptake visible before the vaccinations.
“These changes in PET results after COVID-19 vaccination are significant confusing traps that could lead to unnecessary biopsies and treatments unless properly recognized by the interpreting physicians,” wrote the first author, Dr. Dane Schroeder, a diagnostic radiologist.
Numerous recent case reports and small studies have shown that COVID-19 vaccinations with Moderna and Pfizer products produce minor side effects, including reactive lymphadenopathy. To date, systematic analysis of changes on PET due to COVID-19 vaccination is limited. Managing FDG-hungry lymph nodes in vaccinated patients presents a clinical challenge, especially given the widespread application of PET imaging in oncology, according to the authors.
In this retrospective analysis, researchers sought to assess the frequency and characteristics of abnormal absorption of FDG and C-11 choline on PET imaging performed on cancer patients after COVID-19 vaccination.
The study included 67 patients who had PET / CT or PET / MRI scans with FDG or C-11 choline between December 14, 2020, the first day vaccines were available in the United States, and the 10 March 2021. PET was performed with a median of 13 days after vaccination in patients who received one dose and 10 days after vaccination in patients who received two doses.
Two nuclear medicine physicians independently reviewed the images. Maximum standardized lymph node and deltoid absorption values ​​(SUVmax) greater than the SUV of the blood poolmax were considered positive. All C-11 choline PET scans were performed on patients for evaluation of prostate cancer.
Researchers observed positive axillary lymph node absorption in 10.4% (7/67) of patients undergoing FDG-PET scans and 23.1% (3/13) of patients undergoing choline C PET scans. -11. Ipsilateral deltoid uptake was present in 14.5% (8/55) of patients with documented injection laterality, including in 42.9% (3/7) of patients with positive axillary lymph nodes.
(A) A 57-year-old woman with right arm melanoma who received the first dose of COVID-19 vaccine (Pfizer-BioNTech) in the left deltoid 15 days before FDG PET / CT. Absorption of FDG is observed in the left axillary lymph nodes (arrow, SUVmax = 9.3). (B) A 62-year-old man with metastatic carcinoma of the prostate who received the second dose of COVID-19 vaccine (Pfizer-BioNTech) in the right deltoid seven days before C-11 choline PET / CT . Image courtesy of American Journal of Radiology.
“We did not observe any PET positive axillary lymph nodes beyond 24 days after vaccination. Thus, waiting 3 to 4 weeks after vaccination before undergoing a PET scan for an initial oncology evaluation may also be reasonable, especially in patients with a higher risk of axillary lymph node disease, â€the authors wrote.
Additionally, to avoid pitfalls in interpreting PET imaging at the Mayo Clinic, researchers implemented a new process of verbally screening patients for their vaccination history prior to PET scans because this information did not is not always readily available in their records. The screening data is entered in the patient’s file and made available to the interpreter.
“Interpreting physicians should recognize the characteristics of abnormal PET absorption after COVID-19 vaccination to guide optimal management of follow-up and reduce unnecessary biopsies,” concluded Schroeder and colleagues.
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