PT  - JOURNAL ARTICLE
AU  - Susan Notohamiprodjo
AU  - Matthias Eiber
AU  - Christian Lohrmann
AU  - Wolfgang Andreas Weber
TI  - Temporary reactive response of axillary lymph nodes to COVID-19 vaccination on <sup>18</sup>F-rhPSMA-7.3 PET/CT in patients with prostate cancer
AID  - 10.2967/jnumed.121.263758
DP  - 2022 Mar 01
TA  - Journal of Nuclear Medicine
PG  - jnumed.121.263758
4099  - http://jnm.snmjournals.org/content/early/2022/03/03/jnumed.121.263758.short
4100  - http://jnm.snmjournals.org/content/early/2022/03/03/jnumed.121.263758.full
AB  - Vaccine-associated lymphadenopathy (VAL) is a common finding on 18F-FDG PET/CT examinations following Coronavirus disease 2019 (COVID-19) vaccination. However, data regarding VAL on 18F-rhPSMA-7.3-ligand PET are currently lacking. This study assesses its prevalence, temporal response to vaccination and characteristics of VAL. Methods: 233 consecutive vaccinated and 41 unvaccinated patients with confirmed prostate cancer who underwent 18F-rhPSMA-7.3 PET/CT were retrospectively analyzed. Size and uptake of the axillary lymph nodes were measured. Ratios of SUVmax of ipsilateral to contralateral axillary lymph node (SUVratio) were determined. The characteristics of SUVratio in respect to the duration of PSMA avidity in axillary lymph node after COVID-19 vaccination was analyzed. Results: The prevalence of VAL on 18F-rhPSMA-7.3 PET was 45%. Up to a period of 8 weeks following last COVID-19 vaccination SUVratio was positive (2.05 + 0.17). Thereafter, SUVratio dropped significantly (1.35 + 0.09) and approached the value of unvaccinated group (1.1 + 0.2). SUVratio of metastatic axillary lymph nodes was very high (>11) and can be easily detected visually or semi quantitatively. In 3 patients we observed suspected development and consecutively confirmed involving metastasis of axillary lymph node with SUVratio between 4.0 to 6.6. Correlation between SUVratio and lymph node size (r=0.93, p<0.0001) and lymph node size and duration following vaccine (r=-0.88, p<0.0008) was found. Conclusion: Increased uptake of the PSMA-ligand 18F-rhPSMA-7.3 by axillary lymph nodes is common after COVID-19 vaccination and can persist for 8 weeks. This finding should be considered in the interpretation of 18F-rhPSMA-7.3 PET/CT examinations.