Retrospective Evaluation of NI-RADS for Detecting Postsurgical Recurrence of Oral Squamous Cell Carcinoma on Surveillance CT or MRI

BACKGROUND. Imaging surveillance is important for the early diagnosis of recurrence after definitive treatment of oral squamous cell carcinoma (OSCC). The Neck Imaging Reporting and Data System (NI-RADS) includes a standardized template for surveillance imaging and categorizes probability of recurrence at the primary site and in the neck (cervical lymph nodes) by assigning categories of 1 (no evidence of recurrence), 2 (low suspicion, subdivided into 2a and 2b for the primary site), 3 (high suspicion), and 4 (definite recurrence). OBJECTIVE. The aim of this study was to determine the rate of locoregional and nodal OSCC recurrence stratified by NI-RADS category among patients undergoing surveillance CT or MRI. METHODS. This retrospective study included 158 patients enrolled in an institutional surveillance program after resection of OSCC with curative intent. A total of 503 contrast-enhanced CT or MRI examinations performed during surveillance were evaluated. Each examination was randomly assigned to one of four radiologists with expertise in head and neck imaging, who provided NI-RADS categories for the primary site and the neck (1006 assigned NI-RADS categories). NI-RADS performance in identifying recurrence was assessed by ROC curve analysis. All four readers evaluated 50 randomly assigned cases to determine interreader agreement by use of the Kendall W statistic. RESULTS. Cancer recurrence was confirmed in 7.6% (38/503) of cases for the primary site and in 6.2% (31/503) for the neck. For the primary site, recurrence rates were 1.0% in NI-RADS category 1, 7.1% in category 2a, 5.6% in category 2b, 66.7% in category 3, and 100.0% in category 4. For the neck, recurrence rates were 0.5% in category 1, 7.0% in category 2, 80.0% in category 3, and 100.0% in category 4. NI-RADS had AUC values of 0.934 for the primary site and 0.959 for the neck. Interreader agreement was 0.67 for the primary site and 0.81 for the neck. CONCLUSION. NI-RADS offers excellent discriminatory power in detection of OSCC recurrence, both for the primary site and the neck. CLINICAL IMPACT. Radiologists and maxillofacial surgeons should implement NI-RADS in surveillance regimens for postoperative OSCC to help detect recurrences in an effective and standardized manner using imaging.