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Abstract: Introduction: The utility of obtaining follow up 18-F fluorodeoxyglucose positron emission tomography (FDG PET) imaging in patients with giant cell arteritis (GCA) is unclear. We performed a systematic review and meta-analysis to determine how often vascular FDG PET uptake improves or normalizes in GCA patients after starting immunosuppressive treatment. Methods: An electronic literature search of MEDLINE (Ovid), EMBASE, CINAHL, Scopus, and Cochrane Library from inception through November 4 2020 was performed. Longitudinal studies assessing the correlation of follow-up 18F-FDG PET and clinical or biochemical disease activity in GCA patients receiving treatment were included. Screening, full text review and data extraction was performed by 2 independent reviewers. Meta-analysis of the pooled sensitivity of improved PET for those with clinical or biochemical improvement, and normalized PET for those in clinical remission was performed. Subgroup analyses were performed to examine the tocilizumab-treated patients (TCZ subgroup), studies using international consensus criteria for PET interpretation (CC subgroup), as well as use of hybrid PET/CT (PET/CT subgroup) imaging, and effects of size (Pt Number subgroup). Results: Of 18 included studies, most described improvement of FDG uptake in GCA patients after starting immunosuppressive treatment, but normalization of PET occurred less commonly among patients in remission. The pooled sensitivity of improved PET uptake for those with clinical improvement was 0.85 (95% CI 0.76-0.93, I2=0), the pooled sensitivity of improved PET uptake for those with biochemical improvement was 0.84, (95% CI 0.74-0.93, I2=0), and the pooled sensitivity for normalized PET in those in clinical remission was 0.43 (95% CI 0.34-0.53, I2=9.2). Results were similar in the CC , PET/CT and Pt Number subgroups (pooled sensitivity for PET normalization was 0. 41, 95% CI 0.28, 0.55; 0.43, 95% CI 0.32, 0.55; and 0.41, 95% CI 0.33, 0.51), however more heterogeneity was observed (I2=50.3%, 92.5%, and 95.3% respectively.) The pooled sensitivity for PET normalization improved to 0.80 (95% CI 0.65-0.93, I2=0) in the TCZ subgroup. Conclusion: Vascular FDG uptake improved in the majority (85%) of GCA patients who experienced clinical improvement on treatment and normalized in 43%. Limited data suggested follow up PET scans normalized more often in TCZ-treated patients. Additional prospective longitudinal studies of FDG PET are needed.