Multiparametric positron emission tomography/magnetic resonance imaging in nasopharyngeal carcinoma: Correlations between magnetic resonance imaging functional parameters and 18F-fluorodeoxyglucose positron emission tomography imaging biomarkers and their predictive value for treatment failure

Abstract

Objectives: The clinical significance of positron emission tomography/magnetic resonance imaging (PET/MRI) functional parameters in nasopharyngealcarcinoma (NPC) remains unclear. The purpose of this prospective study was two-fold: (1) to investigate the associations between simultaneously acquired PET/MRI perfusion, diffusion, and glucose metabolism parameters in patients with NPC and (2) to analyze their predictive value with respect to treatment failure.

Materials and methods: We enrolled 85 patients with primary NPC who simultaneously underwent¹⁸F-fluorodeoxyglucose PET/CT and PET/MRI before definitive treatment. The following variables were determined: (1) functional parameters from the MRI component, including perfusion values (K^trans ,k_ep ,v_e , and initial area under the enhancement curve) and apparent diffusion coefficient (ADC) values, and (2) PET parameters, including metabolic tumor volume (MTV). The reciprocal interrelationships between these parameters and their correlations with treatment failure were examined.

Results: We observed significant negative associations between K^trans and ADC (r = -0.215, P = 0.049) as well as between v_e and ADC (r = -0.22, P = 0.04). Correlations between PET and MRI functional parameters were not statistically significant. Treatment failures were observed in 21.2% of patients without distant metastases. Multivariate analysis identified v_e as a significant independent predictor for treatment failure (P = 0.022), whereas MTV showed a borderline significance (P = 0.095). Patients in whom both v_e and MTV values were increased had a significantly higher rate of treatment failure (62.5%) than those with either one (21.9%) or no (7.7%) increased parameter (P = 0.004).

Conclusion: Correlation analyses revealed complex interrelationships among PET and MRI indices measured in patients with NPC. These parameters may have a complementary role in predicting treatment failure in this clinical setting.

Keywords: DCE-MRI; Diffusion-weighted MRI; Nasopharyngeal carcinoma; Positron emission tomography/magnetic resonance imaging; Prognosis.

Figure 1

Correlations between different PET/MRI functional parameters.Scatter diagrams showing the distribution of PET/MRI K^trans in relation to k_ep (panel a), ADC (panel b), and SUV_max (panel c). PET/MRI: Positron emission tomography/magnetic resonance imaging, ADC: Apparent diffusion coefficient, SUV_max: Maximum standardized uptake volume

Figure 2

Boxplots of v_e (a) and MTV (b) categorized by treatment failure status. MTV: Metabolic tumor volume

Figure 3

Dot plots of v_e against MTV categorized by treatment failure status. The horizontal dashed line on the Y-axis indicates the mean v_e value, whereas the vertical dashed line on the X-axis denotes the mean MTV value. Patients with a concomitant increase in both MTV and v_e were characterized by a markedly higher rate of failures compared with those with either one or no increased parameter (P = 0.004). MTV: Metabolic tumor volume

Figure 4

A 77-year-old woman with T4N2M0 NPC. T2-weighted (panel a) and contrast-enhanced T1-weighted images (panel b) revealed the presence of a primary nasopharyngeal neoplasm. The corresponding DCE-MRI image with an overlaid v_e map (panel c) showed a low value (240.79). According to ¹⁸F-FDG PET/MRI (panel d) and PET (panel e) images, the metabolic tumor volume was 8.06. The patient was treated with definitive concurrent chemoradiotherapy. After 2 years of treatment, she is alive without relapses (panel f). The patient had low values of both v_e and MTV. NPC: Nasopharyngeal carcinoma, DCE: Dynamic contrast-enhanced, MRI: Magnetic resonance imaging, PET: Positron emission tomography, ¹⁸F-FDG: ¹⁸F-fluorodeoxyglucose, MTV: Metabolic tumor volume

Figure 5

A 47-year-old male with T4N2M0 NPC. T2-weighted (panel a) and contrast-enhanced T1-weighted images (panel b) revealed the presence of aprimary nasopharyngeal neoplasm. The corresponding DCE-MRI image with an overlaid v_e map (panel c) showed a high value (569.02). According to PET (panel e) and PET/MRI (panel d) images, the metabolic tumor volume was 32.31. The patient was treated with definitive concurrent chemoradiotherapy. After 1 year,treatment failures were identified in a neck lymph node (arrow) and at the ribs (arrowhead; panel f). High values of both v_e and MTV were noted in this patient. NPC: Nasopharyngeal carcinoma, DCE: Dynamic contrast-enhanced, MRI: Magnetic resonance imaging, PET: Positron emission tomography, MTV: Metabolic tumor volume.