Introduction
Cardiac sarcoidosis is an inflammatory granulomatous disease of the heart that carries substantial morbidity and mortality if not properly managed. Immunosuppressive therapy, often steroids, remains the cornerstone of treatment. While traditional imaging modalities help diagnose cardiac involvement, tracking the response to therapy requires reliable, repeatable biomarkers of inflammation. Recent prospective data from a study at Apollo Hospitals, Chennai, suggests that Ga-68 DOTANOC PET/CT—an imaging modality targeting somatostatin receptors—can play a pivotal role in monitoring treatment response in cardiac sarcoidosis.
Why Ga-68 DOTANOC?
Ga-68 DOTANOC binds somatostatin receptor type 2A, which is highly expressed by inflammatory cells in granulomas and minimally present in normal myocardium. Unlike F-18 FDG PET/CT, DOTANOC imaging does not demand stringent dietary preparation, offering a practical advantage in routine clinical practice. The study highlights two key quantitative metrics: maximum standardized uptake value (SUVmax) in the left ventricle and the Disease Activity Score (DAS), defined as the SUVmax ratio between the LV myocardium and blood pool (SUVmed).
Study Overview
Design and participants
In a prospective observational framework conducted between 2022 and 2024 in Chennai, 19 adults with treatment-naïve cardiac sarcoidosis were enrolled. All participants underwent pre- and post-treatment Ga-68 DOTANOC PET/CT scans, complemented by myocardial perfusion imaging and echocardiography to assess functional outcomes such as the left ventricular ejection fraction (LVEF).
Treatment and follow-up
Patients received immunosuppressive therapy, predominantly corticosteroids (prednisolone 0.5 mg/kg/day, tapering over 3–6 months), with occasional second-line agents (methotrexate or cyclophosphamide) in selected cases. The mean duration of treatment was about 13 weeks (range 8–16 weeks). Post-treatment scans were used to evaluate changes in inflammatory activity and myocardial perfusion, alongside clinical status and LVEF changes.
Key Findings
Inflammatory burden and myocardial activity
All patients showed baseline DOTANOC uptake indicating active disease. Post-therapy, 18 of 19 patients demonstrated a significant decline in SUVmax (from 2.67 ± 1.19 to 1.47 ± 0.40; p = 0.001) and in the DAS (from 3.35 ± 1.20 to 1.80 ± 0.52; p = 0.001). Clinically, these biological shifts aligned with symptom improvement and arrhythmia clearance, reducing hospitalizations in the follow-up period.
Functional outcomes and correlations
Of the 14 patients with baseline LV dysfunction (LVEF < 50%), reductions in SUVmax and DAS correlated with improved LVEF (a strong negative relationship: SUVmax correlation = −0.58, p = 0.02; DAS correlation = −0.74, p = 0.002). In many cases, this translated into measurable gains in cardiac function, particularly among those with impaired baseline ejection fractions.
Perfusion and nodal involvement
Areas of increased DOTANOC uptake often coincided with perfusion defects on baseline perfusion imaging, suggesting active inflammation rather than irreversible fibrosis. After treatment, improvements in perfusion paralleled reductions in DOTANOC uptake. Lymph node involvement in the mediastinal, hilar, or axillary regions also showed regression of uptake after therapy, reinforcing the systemic inflammatory nature of sarcoidosis in these patients.
Clinical Implications
The study provides evidence that Ga-68 DOTANOC PET/CT is a viable modality for monitoring response to immunosuppressive therapy in cardiac sarcoidosis. The combined assessment of SUVmax and DAS offers a nuanced view of inflammatory activity, while LVEF trends add a functional perspective. Importantly, DOTANOC imaging may serve as an advantageous alternative or complement to F-18 FDG PET/CT, particularly for patients who struggle with dietary preparation or in whom myocardial suppression is difficult to achieve.
Limitations and Future Directions
Limitations include a relatively small sample size and the potential for time gaps between scans. The authors emphasize that reductions in DOTANOC uptake should be interpreted alongside myocardial perfusion, echocardiography, and clinical status, since inflammation and fibrosis can coexist. Larger, multi-center trials are needed to validate these findings and to refine standardized thresholds for response assessment. Future research could explore the predictive value of DOTANOC metrics for long-term outcomes such as heart failure progression and arrhythmia risk.
Conclusion
Ga-68 DOTANOC PET/CT shows promise as a sensitive tool for assessing treatment response in cardiac sarcoidosis. The observed declines in SUVmax and DAS, together with improvements in LVEF and perfusion, support its role in guiding therapy and monitoring disease activity. As evidence grows, this modality may become an integral part of personalized care for patients with cardiac sarcoidosis.
