The use of MR imaging to detect residual versus recurrent nasopharyngeal carcinoma following treatment with radiation therapy

Objective Residual tumor and fibrosis are commonly observed with magnetic resonance (MR) imaging following radiotherapy for nasopharyngeal carcinoma (NPC). Therefore, MR images of NPC following treatment with radiotherapy were retrospectively analyzed to evaluate whether post-radiation changes associated with residual tumors, recurrent tumors, and fibrosis could be distinguished 1 month and 3–6 months after treatment. Methods MR images were analyzed for 108 patients who completed radiotherapy for NPC and underwent 5-years of follow-up. The presence and incidence of residual tumor versus fibrosis was evaluated and compared with 5-year tumor recurrence rates. Results Residual tumors were detected in 54/108 (50.0%) patients 1 month after radiotherapy, and in 18/108 (16.7%) patients 3–6 months after radiotherapy. Fibrosis was only detected in 59/108 (54.6%) patients 3–6 months after radiotherapy. After 5 years, tumor recurrence occurred in 13/108 (12%) patients, with the average interval between tumor recurrence and the completion of radiotherapy being 29.15 months. In addition, the 1-, 2-, 3-, 4-, and 5-year relapse rates were 1.9%, 5.6%, 9.3%, 11.1%, and 12.0%, respectively. Based on the images analyzed, significant differences in tumor recurrence and residual tumor rate (P = 0.038), and between tumor recurrence and fibrosis (P = 0.021), were observed 1 month and 3–6 months after radiotherapy, respectively. Conclusions In this cohort, tumor recurrence was detected 2–3 year after irradiation and a strong correlation between 5-year recurrence rate and detection of residual tumor or fibrosis by MRI up to six months after radiotherapy was observed.