Correlation between apparent diffusion coefficient and tumor-stroma ratio in hybrid 18F-FDG PET/MRI: preliminary results of a rectal cancer cohort study

Abstract

Background: To explore possible correlations between the tumor-stroma ratio (TSR) and different imaging features of fluorine-18-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging ( 18 F-FDG PET/MRI) in untreated rectal cancer patients.Methods: A patients with rectal cancer were included in this study. All participants were examined preoperatively with whole-body 18 F-FDG PET/MRI. Two pathologists evaluated the TSR of tumors together. Apparent diffusion coefficient (ADC) values and PET-related parameters of the primary lesions were measured and compared between the stroma-high and stroma-low groups. Pearson's correlation or Spearman's rank correlation were used to evaluate the correlation between the ADC values, PET-related parameters, and pathological indices.Results: Our results showed that in the untreated rectal cancer patients, the ADC mean values correlated with the TSR (r=0.327; P=0.007), and stroma-high (low TSR) rectal cancer corresponded to relatively lower ADC mean values (813.54±88.68 vs. 879.92±133.18; P=0.018). The ADC mean and ADC minimum (ADCmin) values were found to be negatively correlated with the pathological T stages (r=−0.384, P=0.001; r=−0.416, P=0.001, respectively) as well as the largest tumor diameters (r=−0.340, P=0.005; r=−0.314, P=0.010, respectively) of rectal cancer. In addition, the pathological T stages correlated with all PET-related metabolic parameters, including mean standard uptake value (SUV), maximum SUV (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) (r=0.338, P=0.006; r=0.350, P=0.004; r=0.326, P=0.007; and r=0.472, P<0.001, respectively). Our results also identified associations between the ADCmin values and SUVmean, SUVmax, P=0.006; P=0.005; P=0.005, respectively). However, there were no statistical correlations between the PET/MRI parameters and the immunohistochemical (IHC) results.Conclusions: This study indicated that the intratumoral heterogeneity measured by PET/MRI may reflect characteristics of the tumor microenvironment. Hence, PET/MRI parameters might be helpful in predicting tumor aggressiveness and prognosis.

The potential application of MR-derived ADCmin values from 68Ga-DOTATATE and 18F-FDG dual tracer PET/MR as replacements for FDG PET in assessment of grade and stage of pancreatic neuroendocrine tumors

“…Consistent with the present results, prior studies have not detected any significant correlations between ADCmean and FDG uptake parameters (FSUVmax, TLG, and MTV) [ 25 , 26 ]. However, a correlation was detected between ADCmin values and MTV, TLG, and FSUVmax values, in line with prior studies on rectal cancer [ 27 ]. This is attributable to the fact that ADCmin values reflect the most highly proliferative areas of tumors and the regions with the greatest cell density [ 28 ].…”

“…1 The correlation between ADCmin and FSUVmax, MTV, and TLG. ADC Apparent diffusion coefficient, SUV Standard uptake value, MTV Metabolic tumor volume, TLG Total lesion glycolysis [27]. This is attributable to the fact that ADCmin values reflect the most highly proliferative areas of tumors and the regions with the greatest cell density [28].…”

Potential use of high-resolution T2-weighted MRI with histopathologic findings in staging esophageal cancer

“…In recent years, PET/MRI has received increasing attention for its potential to improve the accuracy of tumor diagnosis. It has advantages over MRI, such as the ability to combine multiple parameters, high soft tissue resolution, a lack of ionizing radiation, and the means to access the molecular information provided by PET (36,37). This is an avenue of research that will be pursued in the future.…”

The potential application of MR-derived ADCmin values from 68Ga-DOTATATE and 18F-FDG dual tracer PET/MR as replacements for FDG PET in assessment of grade and stage of pancreatic neuroendocrine tumors

“…[25,26] However, a correlation was detected between ADCmin values and MTV, TLG, and FSUVmax values, in line with prior studies on rectal cancer. [27] This is attributable to the fact that ADCmin values re ect the most highly proliferative areas of tumors and the regions with the greatest cell density. [28] As such, tumors exhibiting lower ADCmin values or higher FDG-derived TLG or MTV values are more likely to exhibit a higher Ki-67 index value and more advanced pathological staging such that these parameters have the potential to be used interchangeably when assessing PNET patient grading to guide appropriate patient management efforts.…”