The role of MRI for the diagnosis of recurrence of nasopharyngeal cancer.

Combined radiotherapy and chemotherapy have attained good response rates in the treatment of nasopharyngeal cancer (NPC). Despite excellent response rates to initial treatment, however, five year survival rates are reported to be poor. The reason for this poor prognosis is the high rates of local recurrence and distant metastasis. It is therefore thought to be important to detect local recurrence as early as possible. CT scan is useful in the diagnosis of NPC. Asymmetry of the nasopharyngeal cavity proven by CT suggests NPC, and CT is therefore regarded as important in evaluating the efficacy of therapy. We analyzed CT findings in 23 patients with NPC who were treated in the period from 1986 to 1991. Asymmetry on CT after chemoradiotherapy suggests residual tumor or local recurrence, but 10 patients out of 14 with asymmetry survive without recurrence. False positive rate was 71%. Therefore asymmetry seen on CT does not always mean residual tumor or recurrence. MRI is thought to be superior to CT in the diagnosis of NPC because it can discriminate soft tissue and malignant tumors. Even when fiberscopic examination shows no remarkable findings and CT fails to prove asymmetry of the nasopharyngeal cavity, a high signal area on MRI could suggest local residual tumor or local recurrence. False positive rate of MRI is 17%, which is much superior to CT. Also a low-intensity signal on MRI suggests fibrous tissue rather than tumor. Coronal sections of MRI are also useful in diagnosing the extent of recurrent tumor invading the skull base, mesopharynx, or hypopharynx.(ABSTRACT TRUNCATED AT 250 WORDS)