Thallium-201 SPECT predicts response to intensity-modulated radiation therapy for recurrent oral squamous cell carcinoma

Abstract

SummaryThe aim of this study was designed to investigate the usefulness of thallium-201 single photon emission computed tomography (SPECT) in predicting response of intensitymodulated radiation therapy (IMRT) for recurrent oral squamous cell carcinoma (OSCC). Patients, methods: Thirty-one patients with histologically proven recurrent OSCC were recruited. Before IMRT, all patients underwent SPECT at 15 min and 120 min after intravenous injection 111 MBq of thallous chloride (201Tl). Tumour uptake was measured with the semiquantitative early ratio (ER), delayed ratio (DR), and retention index (RI). The patients were classified into responder (complete response and partial response) and non-responder (stable disease and progressive disease) groups according to the tumour response evaluated by the Response Evaluation Criteria in Solid Tumors guidelines. Results: As comparing DR and RI between the two groups, both parameters were significantly higher in the responder group. When a DR of 1.75 was used as a cutoff value for the responders, the receiver operating characteristic (ROC) analyses revealed sensitivity and specificity of 79% and 75%, respectively. At a cutoff value for the responders of a RI of 78.5%, the ROC analyses showed sensitivity and specificity of 95% and 83%, respectively. Conclusion: Our results suggest that 201Tl-SPECT, as measured by the DR or RI has clinical potential in predicting response of IMRT for patients with recurrent OSCC. The ROC curve analyses further suggest that RI may be superior to DR in distinguishing responders from non-responders.