Thallium-201 single-photon emission tomography in the treatment follow-up of nasopharyngeal carcinoma.

In order to assess the usefulness of thallium-201 single-photon emission tomography (SPET) in the treatment follow-up of nasopharyngeal carcinoma (NPC), a total of 75 201T1 SPET studies were performed in 18 patients with histologically proven NPC. The findings were compared with those of magnetic resonance imaging (MRI) before and after therapy. Four patients received radiotherapy alone while the other 14 received concurrent chemo-radiotherapy. Treatment response was classified as complete (CR) or partial (PR) based on the findings of MRI and 201T1 SPET. Intense 201T1 uptake by the tumour was seen in all 18 patients before treatment. After treatment, MRI showed seven CRs and 11 PRs, whereas 201T1 SPET showed 13 CRs and five PRs. In 12 patients, the results of 201T1 SPET were in agreement with those of MRI. In six patients MRI showed PR but 201T1 showed CR. Follow-up (mean 10.6 months) MRI and 201T1 SPET studies of these six patients revealed that tumour gradually decreased and finally vanished in three patients. This preliminary study indicates that 201T1 SPET has potential in the assessment of early response to treatment of patients with NPC when compared with MRI.