Pediatric Versus Adult Nasopharyngeal Cancer in Diffusion-Weighted Magnetic Resonance Imaging

Abstract

Background: This study aimed at evaluating apparent diffusion coefficient (ADC) values of nasopharyngeal carcinoma (NPC) in the pre-treatment stages of NPC for establishing comparative quantitative parameters between children and adolescents compared to adults. Methods: A retrospective multicentric imaging study was conducted in three medical centers by collecting patient data over a 5-year timeframe. Patients were included in the study based on the following criteria: histopathologically proven carcinoma of the nasopharynx with all available medical records. The total sample included 20 patients (6 pediatric patients and 14 adults). A quantitative analysis of the ADC maps was performed. Two radiologists manually drew the region of interest (ROI) on ADC maps using the whole tumor on all magnetic resonance imaging (MRI) slices. The mean ADC was extracted for each patient and each radiologist's evaluation. Differences in ADC values between pediatric and adult patients were evaluated using an independent samples t-test, with normality and variance assumptions tested via the Shapiro-Wilk and Levene's tests, respectively. p-values less than 0.05 were considered statistically significant. Results: The mean ADC values extracted from the initial pre-treatment diffusion-weighted imaging (DWI) data from magnetic resonance imaging (MRI) in children were 712.22 × 10^-6 mm²/s, compared to adults in whom the mean ADC values were 877.34 × 10^-6 mm²/s. We found a statistically significant difference between the mean ADC values of pediatric patients and adult patients, t (17.44) = -3.15, p = 0.006, with the mean ADC values of pediatric patients (M = 712.22, standard deviation [SD] = 57.03) being lower, on average, than the mean ADC values of adult patients (M = 877.34, SD = 175.25). Conclusions: Our results showed significantly lower ADC values in pediatric patients than in adults, independent of tumor T-stage. Additionally, early-stage tumors, particularly in children, tended to exhibit even lower ADC values, suggesting potential biological distinctions across age groups.

Keywords: adults; diffusion-weighted imaging; magnetic resonance imaging; nasopharyngeal carcinoma; pediatric.

Figure 1

A 13-year-old child with NPC: (A) post-contrast axial T1-weighted imaging showing a large nasopharyngeal mass (red asterisk); (B) axial T2-weighted imaging demonstrating the involvement of the masticatory space (yellow arrow); (C) ADC map showing low signal intensity of the nasopharyngeal mass (white asterisk); (D) ROI was defined by covering as much tumor tissue as possible (shown on the slice with the maximum tumor diameter, orange area).

Figure 2

A 43-year-old male with NPC: (A) post-contrast axial T1-weighted imaging showing a large nasopharyngeal mass (red asterisk); (B) axial T2-weighted imaging demonstrating the involvement of the masticatory space (yellow arrow); (C) ADC map showing low signal intensity of the nasopharyngeal mass (white asterisk); (D) ROI was defined by covering as much tumor tissue as possible (shown on the slice with the maximum tumor diameter, orange area).

Figure 3

Scatter plot of individual ADC values stratified by sample type.

Figure 4

Group differences regarding mean ADC values.

Figure 5

Distribution of apparent diffusion coefficient values by age and tumor stage in pediatric and adult cohorts. ◆ indicates outliers beyond 1.5× the interquartile range (IQR).