Objectives: To decipher the interlinks between PET and DCE kinetic parameters in non-small-cell lung cancer (NSCLC), by using voxel-wise analysis of full dynamic simultaneous [18F]FDG PET-MRI.
Material and methods: Fourteen treatment-naïve patients with biopsy proven NSCLC prospectively underwent a one-hour dynamic [18F]FDG thoracic PET-MRI scan including DCE. The PET and DCE data were normalized to their corresponding T1-weighted MR morphological space, and tumors were masked semi-automatically. Voxel-wise parametric maps of PET and DCE kinetic parameters were computed by fitting the dynamic PET and DCE tumor data to the Sokoloff and Extended Tofts models respectively, by using in-house developed procedures. Curve fitting errors were assessed by computing the relative root mean square error (rRMSE) of the estimated PET and DCE signals at the voxel level. For each tumor, Spearman correlation coefficients (r s ) between all the pairs of PET and DCE kinetic parameters were estimated on a voxel-wise basis, along with their respective bootstrapped 95% confidence intervals (n = 1000 iterations).
Results: Curve fitting metrics provided fit errors under 20% for almost 90% of the PET voxels (median rRMSE,= 10.3, interquartile ranges IQR = 8.1; 14.3), whereas 73.3% of the DCE voxels showed fit errors under 45% (median rRMSE = 31.8%, IQR = 22.4; 46.6). The PET-PET, DCE-DCE and PET-DCE voxel-wise interlinks were heterogeneous, with variations related to individual tumor behaviors. Beyond this wide variability, the PET-PET and DCE-DCE interlinks were mainly high (absolute r s values > 0.7), whereas the PET-DCE interlinks were mainly low to moderate (absolute r s values < 0.7). Half the tumors showed an hypometabolic with low perfused/vascularized profile, a hallmark of hypoxia and tumor aggressiveness.
Conclusion: The interlinks between dynamic PET and DCE kinetic parameters assessed simultaneously with [18F]FDG PET-MRI are heterogeneous among NSCLC tumors. In the era of precision medicine, PET-MRI has unique capability to go further insight the individual tumor behavior in NSCLC.