[89Zr]-immuno-PET prediction of response to rituximab treatment in patients with therapy refractory interstitial pneumonitis: a phase 2 trial

INTRODUCTION

Immune-mediated interstitial pneumonitis may be treated with anti-CD20 therapy after failure of conventional therapies. However, clinical response is variable. It was hypothesized that autoreactive CD20-positive cells may play an important role in this variability. This prospective study aims to elucidate if imaging of CD20-positive cells in the lungs allows prediction of the response to anti-CD20 treatment.

METHODS

Twenty-one patients with immune-mediated interstitial lung disease (ILD) with deteriorated pulmonary function received a dose of 1000 mg rituximab on day 1 and day 14 spiked with a tracer dose of radiolabeled [89Zr]-rituximab. PET/CT was performed on days 3 and 6. Standardized uptake values (SUV) were calculated as a measure for pulmonary CD20 expression. Based on pulmonary function tests (PFT), forced vital capacity (FVC), and diffusing capacity for carbon monoxide (DLCO), prior to and 6 months after treatment, patients were classified as responder (stable disease or improvement) or non-responder.

RESULTS

Fifteen patients (71%) were classified as responder. Pulmonary [89Zr]-rituximab PET SUVmean was significantly correlated with the change in FVC and DLCO (K = 0.49 and 0.56, respectively) when using target-to-background ratios, but not when using SUVmean alone. [89Zr]-rituximab SUVmean was significantly higher in responders than in non-responders (0.35 SD 0.09 vs. 0.23 SD 0.06; P = 0.02).

CONCLUSION

Rituximab treatment was effective in the majority of patients. As a higher pulmonary uptake of [89Zr]-rituximab correlated with improvement of PFT and treatment outcome, [89Zr]-rituximab PET imaging may serve as a potential predictive biomarker for anti-CD20 therapy.

TRIAL REGISTRATION

Clinicaltrials.gov identifier NCT02251964.

18F-FDG PET as a predictor of pulmonary function in sarcoidosis

PURPOSE

Fluor-18 fluorodeoxyglucose (18F-FDG) PET is able to demonstrate sarcoidosis activity. Ongoing pulmonary sarcoidosis activity can be reflected by a decline in pulmonary function tests (PFT). To assess whether diffuse metabolic activity of the lung parenchyma imaged by 18F-FDG PET predicts future pulmonary deterioration, 18F-FDG PET was compared with PFT.

METHODS

In this retrospective cohort study, 43 newly diagnosed, sarcoidosis patients were analyzed. Based on 18F-FDG PET, patients were diagnosed with diffuse parenchymal disease activity, without or with immunosuppressive treatment, started after 18F-FDG PET was performed. As a control, sarcoidosis patients with mediastinal/hilar disease activity but without metabolic activity in the lung parenchyma were analyzed, all without treatment. Vital capacity (VC), forced expiratory volume (FEV1) and diffusion capacity of the lung for carbon monoxide (DLCO) were analyzed per group at baseline, i.e., at the time 18F-FDG PET was performed, and after one year follow-up.

RESULTS

At follow-up, a significant decrease in DLCO was found in untreated patients with diffuse parenchymal activity. No change in VC or FEV1 could be observed. Treated patients with parenchymal activity showed a significant increase in VC, FEV1 and DLCO, while patients without parenchymal activity did not show any change in PFT.

CONCLUSIONS

In sarcoidosis, diffuse parenchymal disease imaged by 18F-FDG PET, predicts a future deterioration of DLCO when untreated. Treatment however, improves VC, FEV1 and DLCO significantly suggesting that 18F-FDG PET represents the pulmonary improvement that can be achieved. The absence of metabolic activity in the lung parenchyma justifies a wait-and-see policy.

Imaging the inflammatory activity of sarcoidosis: sensitivity and inter observer agreement of (67)Ga imaging and (18)F-FDG PET

AIM

The aim of this study was to investigate sensitivity of 67Ga imaging and 18F-FDG PET for sarcoidosis activity and their inter observer variability.

METHODS

Thirty-four newly diagnosed, histologically proven sarcoidosis patients were analyzed prospectively. (67)Ga imaging and (18)F-FDG PET were performed, the presence of pulmonary and extra pulmonary lesions was evaluated and inter observer variability of both techniques was assessed.

RESULTS

Overall sensitivity to detect active sarcoidosis was 88% for (67)Ga imaging and 97% for (18)F-FDG PET. Although these results were not significantly different, 18F-FDG PET detected more lesions in the mediastinum (P<0.05), hila (P<0.05), lymph nodes (P<0.001) and extra pulmonary regions in general (P<0.001). Inter observer agreement was poor to moderate for (67)Ga imaging (kappa 0.19-0.59) and good to very good for (18)F-FDG PET (kappa 0.65-1.00).

CONCLUSION

(18)F-FDG PET is more sensitive than (67)Ga imaging in the assessment of sarcoidosis activity with regard to the mediastinum, hila, lymph nodes and extra pulmonary lesions in general. Furthermore, (18)F-FDG PET demonstrates a very good inter observer agreement in contrast with (67)Ga imaging and (18)F-FDG PET is therefore the nuclear imaging technique of choice in sarcoidosis assessment.