The current study importantly showed that the metabolism-vascularity relationship varies with histologic subtypes of NSCLC, with AC having a negative correlation, but not in SCC. Shastry et al found that low metabolism with high vascularity was a feature of AC whilst high metabolism with high vascularity was a feature of SCC. The findings of the current study reinforce their previous findings. Adenocarcinomas were more likely to have low metabolism and high vascularity, which could partly account for the negative correlation in AC in our results. Previous studies using PET tracers have also found that the balance between blood flow and metabolism may provide prognostic/predictive information. Although it is reasonable to hypothesize that the metabolic requirements of tumors are mirrored by alterations in tumor haemodynamics, an association between mismatched tumor blood flow and metabolism and adverse tumor biology has been illustrated by many studies. Aronen et al. found that uncoupling of vascularity and metabolism was a feature of Saikosaponin-C high-grade gliomas; Mankoff et al. showed that breast cancers with a high ratio of glucose metabolism to perfusion were less likely to respond favorably to treatment; Komar at al. observed that both malignant and benign pancreatic lesions were associated with decreased perfusion, and in patients with malignant diseases, a high ratio of metabolism to blood flow seemed to predict poor survival. Mankoff at al. commented on the work of Komar that although tightly coupled in most normal tissues, blood flow and metabolism are often not well matched in tumors. A flow-metabolism mismatch, specifically, high metabolism relative to blood flow, can be recognized in tumors by functional and molecular imaging and is associated with poor response to treatment and early relapse or disease progression. We speculated that the decorrelation of tumor vascularity and glucose metabolism may underlie the relative poor outcome in SCC of lung in Chinese. It would be interesting to investigate whether the metabolism-vascularity relationship may predict the prognosis, and as such, a longitudinal study could be useful. Some limitations should be mentioned in our study. The presence of hypoxia in the tissue microenvironment which may increase the FDG-SUV, the microscopic necrotic foci with reduced DCE-MRI parameters, the potential influence of tumor heterogeneity in large tumors that may contain some latent metabolic potential, the presence of partial volume effects that may hamper the DCE-MRI and SUV measurements, the limitations of the applied pharmacokinetic model and the static SUV estimation in the metabolic phase are possible limiting factors in the validation of the association between the DCE-MRI parameters and the metabolic activity of lung cancer. To confirm the relationship between the uncoupling of tumor vascularity and glucose metabolism and clinical outcome in NSCLC subtypes, longitudinal study is needed. Given the effects of Artemisinic-acid respiratory movement, although we have taken measures in the DCE-MRI data acquisition and processing procedure, we couldn’t completely overcome the confounding. In conclusion, AC and SCC showed different patterns in both tumor vascularity and 
glucose metabolism.