Cancer patients who have received mRNA vaccines to prevent COVID-19 can experience abnormal activity or swelling of lymph nodes on their PET scans which could be mistaken for a worsening of their cancer, a new Yale study shows. One in four cancer patients who had received two doses of either Moderna or Pfizer vaccines at Yale New Haven Hospital had abnormal axillary (armpit) lymph nodes on PET scans, on the same side as vaccine injection, which may be mistaken for cancer spreading through the body.
“It is crucial for ordering doctors and radiologists to ascertain vaccination status of their patients to avoid unnecessary anxiety and treatments, but also to be vigilant in monitoring these patients in case abnormal lymph nodes actually indicate worsening of cancer,” said Yale’s Darko Pucar, co-director of the Molecular Imaging Clinical and Translational Research Laboratory and senior author of the study. Cancer patients should also make sure they receive vaccinations in the arm opposite of the side of the prior or suspected cancer site, Pucar said. The research was published in the journal JAMA Oncology.