Objective. [18F]Fluorodeoxyglucose (18F-FDG) PET/CT is increasingly used to assess organ involvement and response to treatment in IgG4-related disease (IgG4-RD), but clear correlations between 18F-FDG uptake and disease activity have not been established yet. We aimed to correlate the intensity and distribution of 18F-FDG uptake with validated clinical, serological and immunological parameters of IgG4-RD activity. Methods. Twenty patients with active IgG4-RD underwent a baseline 18F-FDG PET/CT. Ten patients repeated 18F-FDG PET/CT after immunosuppressive treatments. 18F-FDG tissue uptake was measured using the standardized uptake value corrected for the partial volume effect (PVC-SUV) and the total lesion glycolysis (TLG) with (TLGtot+ln) and without (TLGtotln) lymph nodes. Disease activity was assessed by means of clinical parameters [IgG4-RD Responder Index (RI)], serological (ESR and CRP) and immunological (serum IgG4 and circulating plasmablasts) biomarkers. The enhanced liver fibrosis score was exploited as a biomarker for fibroblast activation. Results. Thirteen (65%) patients had two or more organs affected by IgG4-RD. All patients had active IgG4-RD as defined by a median IgG4-RD RI value of 9 (range 615; normal < 3). Serum IgG4 and plasmablasts were elevated in 85% of patients. Circulating plasmablasts positively correlated with PVCSUV (P = 0.027), inversely correlated with TLGtotln (P = 0.023) and did not correlate with TLGtot+ln (P > 0.05). No statistically significant correlation was found between PVC-SUV or TLG and IgG4-RD RI, ESR, CRP, serum IgG4 or enhanced liver fibrosis score (P > 0.05). Clinical response to immunosuppressive therapies was associated with a consensual reduction of circulating plasmablasts, PVC-SUV, TLGtot+ln and TLGtotln values (P < 0.05 for all comparisons). Conclusions. 18F-FDG uptake of IgG4-RD lesions reflects immunological perturbations of the B cell compartment rather than fibroblast activation and extracellular matrix deposition. Conventional biomarkers of disease activity, namely IgG4-RD RI, ESR, CRP and serum IgG4 levels, do not appear to correlate with the radiometabolic activity of IgG4-RD lesions. In light of our results PET/CT represents a reliable instrument for assessing IgG4-RD activity, although lymph-node uptake deserves careful interpretation.

Quantitative measurement of 18F-FDG PET/CT uptake reflects the expansion of circulating plasmablasts in IgG4-related disease / Berti, A; Della-Torre, E; Gallivanone, F; Canevari, C; Milani, R; Lanzillotta, M; Campochiaro, C; Ramirez, Ga; Bozzalla Cassione, E; Bozzolo, E; Pedica, F; Castiglioni, I; Arcidiacono, Pg; Balzano, G; Falconi, M; Gianolli, L; Dagna, L. - In: RHEUMATOLOGY. - ISSN 1462-0324. - 2017, 56:12(2017), pp. 2084-2092. [10.1093/rheumatology/kex234]

Quantitative measurement of 18F-FDG PET/CT uptake reflects the expansion of circulating plasmablasts in IgG4-related disease.

Berti A
Primo
;
2017-01-01

Abstract

Objective. [18F]Fluorodeoxyglucose (18F-FDG) PET/CT is increasingly used to assess organ involvement and response to treatment in IgG4-related disease (IgG4-RD), but clear correlations between 18F-FDG uptake and disease activity have not been established yet. We aimed to correlate the intensity and distribution of 18F-FDG uptake with validated clinical, serological and immunological parameters of IgG4-RD activity. Methods. Twenty patients with active IgG4-RD underwent a baseline 18F-FDG PET/CT. Ten patients repeated 18F-FDG PET/CT after immunosuppressive treatments. 18F-FDG tissue uptake was measured using the standardized uptake value corrected for the partial volume effect (PVC-SUV) and the total lesion glycolysis (TLG) with (TLGtot+ln) and without (TLGtotln) lymph nodes. Disease activity was assessed by means of clinical parameters [IgG4-RD Responder Index (RI)], serological (ESR and CRP) and immunological (serum IgG4 and circulating plasmablasts) biomarkers. The enhanced liver fibrosis score was exploited as a biomarker for fibroblast activation. Results. Thirteen (65%) patients had two or more organs affected by IgG4-RD. All patients had active IgG4-RD as defined by a median IgG4-RD RI value of 9 (range 615; normal < 3). Serum IgG4 and plasmablasts were elevated in 85% of patients. Circulating plasmablasts positively correlated with PVCSUV (P = 0.027), inversely correlated with TLGtotln (P = 0.023) and did not correlate with TLGtot+ln (P > 0.05). No statistically significant correlation was found between PVC-SUV or TLG and IgG4-RD RI, ESR, CRP, serum IgG4 or enhanced liver fibrosis score (P > 0.05). Clinical response to immunosuppressive therapies was associated with a consensual reduction of circulating plasmablasts, PVC-SUV, TLGtot+ln and TLGtotln values (P < 0.05 for all comparisons). Conclusions. 18F-FDG uptake of IgG4-RD lesions reflects immunological perturbations of the B cell compartment rather than fibroblast activation and extracellular matrix deposition. Conventional biomarkers of disease activity, namely IgG4-RD RI, ESR, CRP and serum IgG4 levels, do not appear to correlate with the radiometabolic activity of IgG4-RD lesions. In light of our results PET/CT represents a reliable instrument for assessing IgG4-RD activity, although lymph-node uptake deserves careful interpretation.
2017
12
Berti, A; Della-Torre, E; Gallivanone, F; Canevari, C; Milani, R; Lanzillotta, M; Campochiaro, C; Ramirez, Ga; Bozzalla Cassione, E; Bozzolo, E; Pedica, F; Castiglioni, I; Arcidiacono, Pg; Balzano, G; Falconi, M; Gianolli, L; Dagna, L
Quantitative measurement of 18F-FDG PET/CT uptake reflects the expansion of circulating plasmablasts in IgG4-related disease / Berti, A; Della-Torre, E; Gallivanone, F; Canevari, C; Milani, R; Lanzillotta, M; Campochiaro, C; Ramirez, Ga; Bozzalla Cassione, E; Bozzolo, E; Pedica, F; Castiglioni, I; Arcidiacono, Pg; Balzano, G; Falconi, M; Gianolli, L; Dagna, L. - In: RHEUMATOLOGY. - ISSN 1462-0324. - 2017, 56:12(2017), pp. 2084-2092. [10.1093/rheumatology/kex234]
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