Abstract
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Introduction: 11C-PIB PET/CT has shown promise as a specific and non-invasive method for the diagnosis of cardiac amyloidosis (CA). The clinical risk stratification of patients with amyloid light-chain CA (AL-CA) still remained unclear. This prospective study evaluated 11C-PIB PET/CT of AL-CA in correlation with clinical staging and explored the potentials in therapy response.
Methods: This prospective study recruited 51 patients (age, 59.8±7.7 years; M/F, 34/17) with known AL-CA and 14 control patients (age, 58.9±8.2 years; M/F, 9/5; including 8 healthy controls and 6 non-amyloid hypertrophic). Subjects underwent echocardiography,a 11C-PIB-PET/CT 30min dynamic scan (SinoUnion PoleStar m660, China) after radiotracer injection with a dose of 415.3±116.0 MBq. Two simple semiquantitative approaches, standardized uptake value ratio (SUVR) and retention index (RI) were established for 11C-PIB analysis. The retention index (RI) derived from the time activity curve (TAC) was defined as the mean standardized uptake value (SUVmean) of the myocardial VOI from 10 to 20 min divided by the integral of the mean SUV of the left atrium (LA) blood VOI from 0 to 15 min. The standardized uptake value ratio (SUVR) was also defined as the SUVmean of the myocardial divided by the SUVmean of the LA. Additionally, the correlation between dynamic PET/CT parameters and clinical, echocardiography parameters were also assessed.
Results: Patients with AL-CA displayed an elevated cardiac uptake in comparison to controls presenting SUVR: 5.29±3.66) vs. controls (1.46±0.36, P=0.0002), as well as RI (0.159±0.11 vs. 0.038±0.01, P=0.0001). For identifying AL-CA, a cut-off value of 1.92 for SUVR showed a sensitivity of 90.2% and a specificity of 92.9% (AUC: 97.3% [95% CI]: 94% to 100%]) and a cut-off value of 0.053 for RI showed 100% sensitivity and specificity (AUC: 100%, 95%CI: 100%-100%). Association of dynamic PET/CT parameters and clinical features are shown in Table S1. Notably, Both SUVR and RI were significantly associated with NT-proBNP (P=0.019, P=0.006). SUVR was associated with left atrial diastolic diameter (LAD) (P=0.013). Six patients underwent follow-up 11C-PIB PET/CT after 9 cycles of chemotherapy. According to the consensus response criteria, 4 patients had a complete response and 2 patients had a very good partial response. Most patients showed a medium or marked reduction of cardiac uptake in 11C-PIB dynamic PET/CT, especially for myocardial RI and SUVmean (Figure S1). Patient case demonstrated lower myocardial uptake of posttreatment comparing with baseline scan, which can be observed by 11C-PIB PET/CT images as well as the corresponding TACs in Figure 1.
Conclusions: 11C-PIB PET was highly accurate in detecting AL-CA. 11C-PIB dynamic parameters were associated with several clinical parameters, which may potentially reflect disease burden and risk stratification. In addition, its value in the therapy response is promising.
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