PET/MR Imaging in Evaluating Treatment Failure of Head and Neck Malignancies: A Neck Imaging Reporting and Data System-Based Study

Abstract

Background and purpose: PET/MR imaging is a relatively new hybrid technology that holds great promise for the evaluation of head and neck cancer. The aim of this study was to assess the performance of simultaneous PET/MR imaging versus MR imaging in the evaluation of posttreatment head and neck malignancies, as determined by its ability to predict locoregional recurrence or progression after imaging.

Materials and methods: The electronic medical records of patients who had posttreatment PET/MR imaging studies were reviewed, and after applying the exclusion criteria, we retrospectively included 46 studies. PET/MR imaging studies were independently reviewed by 2 neuroradiologists, who recorded scores based on the Neck Imaging Reporting and Data System (using CT/PET-CT criteria) for the diagnostic MR imaging sequences alone and the combined PET/MR imaging. Treatment failure was determined with either biopsy pathology or initiation of new treatment. Statistical analyses including univariate association, interobserver agreement, and receiver operating characteristic analysis were performed.

Results: There was substantial interreader agreement among PET/MR imaging scores (κ = 0.634; 95% CI, 0.605-0.663). PET/MR imaging scores showed a strong association with treatment failure by univariate association analysis, with P < .001 for the primary site, neck lymph nodes, and combined sites. Receiver operating characteristic curves of PET/MR imaging scores versus treatment failure indicated statistically significant diagnostic accuracy (area under curve range, 0.864-0.987; P < .001).

Conclusions: Simultaneous PET/MR imaging has excellent discriminatory performance for treatment outcomes of head and neck malignancy when the Neck Imaging Reporting and Data System is applied. PET/MR imaging could play an important role in surveillance imaging for head and neck cancer.

FIG 1.

ROC curves for the performance of PET/MR imaging–based NI-RADS for discriminating treatment failure or no treatment failure. Blue curves reflect the performance of PET/MR imaging for the primary site, neck lymph nodes, and all sites combined. Inflection points in the curves are discrimination points between NI-RADS 1 and 2 and 2 and 3. The red diagonal curve is a reference. The AUC is reported for each curve, with values >0.500 signifying good performance of the test to discriminate treatment failure.

FIG 2.

Conspicuity of disease recurrence with PET/MR imaging. Coronal T1WI post gadolinium (A) shows subtle enhancement along the right soft palate (arrow) in a patient with history of treated SCC. Fused coronal PET/MR imaging (B) demonstrates avid FDG uptake at the area of enhancement (arrow), which was recurrent SCC on biopsy and subsequently treated with wide local excision. Postresection axial T1WI postgadolinium sequence (C) shows ill-defined enhancement in the right oropharynx (arrow) with corresponding avid FDG uptake (D), which was biopsy-proved as SCC.

FIG 3.

PET/MR imaging to evaluate perineural spread of adenoid cystic carcinoma. Coronal T1WI postgadolinium (A) and coronal fused PET/MR imaging (B) of a patient with a history of left maxillary sinus adenoid cystic carcinoma status post resection and radiation. On this initial posttreatment PET/MR imaging, the enhancing tissue along the thickened extraocular muscles (arrow) and infraorbital foramen (dashed arrow) of the left orbit corresponds to areas of increased FDG uptake and increased metabolic activity. The site was scored as NI-RADS 3 at consensus. The patient underwent orbital exenteration, with surgical pathology positive for perineural spread of tumor.

FIG 4.

Interreader variability in the interpretation of PET/MR imaging–based NI-RADS. Axial T1WI postgadolinium sequence (A) and axial fused PET/MR imaging (B) in a patient with a history of maxillary sinus SCC status post subtotal maxillectomy and radiation. On the initial posttreatment PET/MR imaging, enhancing tissue in the pterygopalatine fossa (arrow) does not have corresponding FDG uptake. This primary site finding was scored a 2 by 1 reader (for discordant PET and MR imaging findings) and as a 1 by the other reader (for expected treatment related change). The patient has no evidence of recurrence on follow-up imaging nor clinical evidence of recurrence. In these scenarios, although agreement may not be perfect, the linked NI-RADS management decision of “short interval follow-up” allows these patients to be correctly risk-stratified.