Correlations between DW-MRI and 18 F-FDG PET/CT parameters in head and neck squamous cell carcinoma following definitive chemo-radiotherapy

Abstract

Background: Posttreatment diffusion-weighted magnetic resonance imaging (DW-MRI) and 18F-fluorodeoxygluocose (¹⁸ F-FDG) positron emission tomography (PET) with computed tomography (PET/CT) have potential prognostic value following chemo-radiotherapy (CRT) for head and neck squamous cell carcinoma (HNSCC). Correlations between these PET/CT (standardized uptake value or SUV) and DW-MRI (apparent diffusion coefficient or ADC) parameters have only been previously explored in the pretreatment setting.

Aim: To evaluate stage III and IV HNSCC at 12-weeks post-CRT for the correlation between SUV_max and ADC values and their interval changes from pretreatment imaging.

Methods: Fifty-six patients (45 male, 11 female, mean age 59.9 + - 7.38) with stage 3 and 4 HNSCC patients underwent 12-week posttreatment DW-MRI and ¹⁸ F-FDG PET/CT studies in this prospective study. There were 41/56 patients in the cohort with human papilloma virus-related oropharyngeal cancer (HPV OPC). DW-MRI (ADC_max and ADC_min) and ¹⁸ F-FDG PET/CT (SUV_max and SUV_max ratio to liver) parameters were measured at the site of primary tumors (n = 48) and the largest lymph nodes (n = 52). Kendall's tau evaluated the correlation between DW-MRI and ¹⁸ F-FDG PET/CT parameters. Mann-Whitney test compared the post-CRT PET/CT and DW-MRI parameters between those participants with and without 2-year disease-free survival (DFS).

Results: There was no correlation between DW-MRI and ¹⁸ F-FDG PET/CT parameters on 12-week posttreatment imaging (P = .455-.794; tau = -0.075-0.25) or their interval changes from pretreatment to 12-week posttreatment imaging (P = .1-.946; tau = -0.194-0.044). The primary tumor ADC_mean (P = .03) and the interval change in nodal ADC_min (P = .05) predicted 2-year DFS but none of the ¹⁸ F-FDG PET/CT parameters were associated with 2-year DFS.

Conclusions: There is no correlation between the quantitative DWI-MRI and ¹⁸ F-FDG PET/CT parameters derived from 12-week post-CRT studies. These parameters may be independent biomarkers however in this HPV OPC dominant cohort, only selected ADC parameters demonstrated prognostic significance. Study was prospectively registered at http://www.controlled-trials.com/ISRCTN58327080.

Keywords: carcinoma; chemo-radiotherapy; diffusion-weighted magnetic resonance imaging; head and neck cancer; positron emission tomography; posttreatment; squamous cell.

FIGURE 1

Participant flow chart

FIGURE 2

Scatter plots of SUV_max vs ADC_mean at 12‐weeks post CRT for (A) primary tumor and (B) lymph node as well as scatter plots for changes in SUV_max vs changes in ADC_mean from pretreatment to 12‐week posttreatment for (C) primary tumor and (D) lymph node. PET measures (y‐axes) and MRI measures (x‐axes). Line of best fit (blue) with 95% confidence intervals shown overlaid (grey)

FIGURE 3

Pretreatment MRI and FDG PET/CT study in a 64‐year‐old male patient with T2N2b left oropharynx tumor. T2W, b = 800 DWI and ADC map (b = 100‐800) MRI images (A and C) and CT, PET, PET/CT fused images (B and D) indicating the left glosso‐tonsillar sulcus tumor (arrows in A and B) and left level 2 lymph node (arrows in C and D). The ROIs on the MRI study include areas of increased DWI signal corresponding to intermediate T2w signal in the cores of the primary and nodal tumor as indicated (ovals in A and C). The 6 mm VOI on the PET‐CT study is seen within the central portion of the primary and nodal tumor (circles in B and D)

FIGURE 4

12‐week post‐chemo‐radiotherapy MRI and PET/CT study in the same patient. T2w, b = 800 DWI and ADC map (b = 100‐800) MRI images (A and C) and CT, PET, PET/CT fused image (B and D) indicating the site of the previous left glosso‐tonsillar sulcus tumor, which is now nonmeasurable and left level 2 lymph node, which has markedly reduced in size (arrows in C and D). The 6 mm ROIs on the MRI study are placed at the site of the previous primary tumor (circle in A) and at the residual nodal tumor as indicated (circle in B). The corresponding 6 mm VOI on the PET‐CT study is seen within the central portion of the primary and nodal tumor (circles in B and D)