18F-fluoro-deoxy-glucose positron emission tomography combined with computed tomography can reliably rule-out infection and cancer in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis suspected of disease relapse

Abstract

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of autoimmune diseases characterized by systemic inflammation in small- to medium-sized blood vessels. Although immunosuppressive therapy has greatly improved the prognosis for these patients, there are still significant comorbidities, such as cancer and infection, associated with AAV. These comorbidities are often indistinguishable from an underlying AAV disease relapse, and create a clinical conundrum, as these conditions are normally contraindications for immunosuppressive treatment. Thus, it is important to be able to rule out these comorbidities before initiation of immunosuppressive treatment. We examined 18F-fluoro-deoxy-glucose positron emission tomography combined with computed tomography (FDG-PET/CT)'s value in ruling out cancer or infection in patients with AAV.Data were obtained retrospectively for a clinically based cohort of AAV patients who underwent FDG-PET/CT during 2009 to 2014 owing to a suspicion of cancer, infection, or both cancer and infection indistinguishable from disease relapse. FDG-PET/CT conclusions were compared to the final diagnoses after follow-up analysis (mean 43 months).A total of 19 patients were included who underwent a total of 26 scans. The results of FDG-PET/CT outcome compared to final diagnosis were: 9 true positives, 3 false positives, 13 true negatives, and 1 false negative. The diagnostic probabilities for FDG-PET/CT with respect to overall comorbidity (i.e., cancer or infection) were: sensitivity 90% ( 95% confidence interval [CI] 60%–98%), specificity 81% ( 95% CI 57%–93%), positive predictive value 75% (95% CI 47%–91%), negative predictive value 93% (95% CI 68%–99%), and accuracy 84% (95% CI 66%–94%).FDG-PET/CT had a high negative predictive value and ruled out the comorbidities correctly in all but one case of urinary tract infection, a well-known limitation. Our study showed FGD-PET/CT's promise as an effective tool for ruling out cancer or infection in patients with AAV albeit in a limited population.

Clinical value of 18F-FDG-PET/CT in suspected serious disease with special emphasis on occult cancer

“…At the time of FDG administration, all patients had fasted for at least 6 hours. 18 F-FDG-PET/CT image acquisition commenced 60±5 minutes after the administration of a weight adjusted dose of 4 MBq/kg FDG (200-400MBq) [13].…”

Granulomatosis with polyangiitis; activation or infection?

“…İmmünsüpresif tedavi ile prognoz iyileşme göstermiştir, fakat tedavi ile ilişkili komorbiditeler endişe olarak kalmaya devam etmektedir (6). Granülomatöz polianjiit tanılı hastanın izleminde hastalığın doğasına veya tedaviye bağlı olarak enfeksiyon riski artmaktadır (7).…”

“…Bizim olgumuzda da başlangıçtan ex olana kadar akut faz yanıtları yüksek saptanmış olup, klinik olarak bunların ayrımının yapılabilmesi zorlaşmaktadır. Hastalık aktivasyonu, enfeksiyon ve malignite ayrımı için pozitron emisyon tomografisi (PET) ve BT birleşimi ile ayrım yapabileceğini gösteren çalışmalar olmakla beraber klinik uygulaması çok kolay değildir (7).…”

“…Tanıdan sonraki ilk yıl içinde ölümlerin en önemli nedenini enfeksiyonlar oluşturmaktadır (6). Hastalık aktivitesine ve immünsüpresif tedaviye göre enfeksiyon gelişme riski artmaktadır (7).…”

Potential Applications of PET Scans, CT Scans, and MR Imaging in Inflammatory Diseases

“…Same group reported two cases of asymptomatic aortic arch involvement in ANCAassociated vasculitis diagnosed with FDG-PET/CT (73). Finally, a small retrospective study from Frary et al found FDG-PET/CT to have high accuracy and predictive values for differentiating disease relapse of ANCA-associated vasculitides from infection and malignancies, two important differential diagnoses with often indistinguishable symptoms and signs (74).…”