Evaluation of changes in lymph node size and metabolism by PET CT in patients with cancer who have been immunized against COVID 19: A Mexican study.
Authors: Camarin Sanchez Efrain Isaias , Enciso López Ervin Saúl , Shveid Gerson Daniela , Rodriguez Benigno , Serrano Villamayor Omar , Nehmad Cecilia , Tovar Cabrera Juan Manuel , Bonilla Molina Diana , Gerson Raquel , Olivares Guillermo 
Published: June 2022

e13647 Background: The risk of developing COVID-19 in patients with cancer has increased, directly influenced by age and the magnitude of comorbidities. In this population, the estimated mortality is 10.9%. With this, the urgent need for patients with cancer to get vaccinated against SARS COV 2 has generated an international response. With the ongoing vaccination campaign, experts in nuclear medicine have observed an increment in lymph node uptake in PET CT with 18 FDG. Increased uptake in lymph nodes in patients with a neoplastic diagnosis on PET CT 18 FDG must be closely followed and well-studied to differentiate disease progression from an inflammatory, fleeting reaction. Methods: Amongst the inclusion criteria were patients over 18 years of age with solid tumors, including lymphomas, who were on active oncologic treatment with chemotherapy, immune therapy, radiotherapy or under surveillance between April 2021 and July 2021 who underwent a PET CT scan and had at least one dose of a COVID 19 vaccine, and a prior PET CT to the vaccine for comparison. Patients were excluded who showed evidence of progression or disease recurrence of the primary tumor. We evaluated lymph node size and metabolism measured by SUV max in the PET CT scan prior to being vaccinated and posterior to, as well as patients’ clinical characteristics. Results: A total of 92 patients who met inclusion criteria were included in the study. Amongst those, 54.3% were women, the median age was 68 years (27 - 95 years), the most common neoplastic diagnoses were breast cancer (19.6%), gastrointestinal tumors (17.4%), urothelial tumors (9.8%), lymphomas (9.8%) and ovarian cancer (8.7%). 52.2% of patients were under surveillance and 47.8% were under active treatment. 79% of patients had at least 2 vaccine doses. 59% had received Pfizer vaccines and the measurable adenopathies were axillary in 32.7% and mediastinal in 27%. The medium size of the measured lymph nodes prior to receiving the vaccine was 2.86 mm with an SUV max of 1.24, while after vaccination were 6.01 and 2.27 respectively. A Kruskal Wallis test was conducted to compare median results according to histopathologic reports, with no statistical difference. A Mann Whitney U test was conducted to compare breast cancer to other cancer histologies, where a statistical difference was found for SUV max, p = 0.003 and size with p = 0.033. Conclusions: This work details significant differences between lymph node size and SUV max in oncologic patients pre and post vaccination for COVID 19, showing a statistical difference in patients with breast cancer. This increment in lymph node uptake in patients with a neoplastic diagnosis PET CT 18 FDG must be closely followed and well-studied to differentiate disease progression from an inflammatory reaction.