Amide proton transfer MRI detects early changes in nasopharyngeal carcinoma: providing a potential imaging marker for treatment response.

PURPOSE: To determine if treatment of nasopharyngeal carcinoma (NPC) induces early changes in amide proton transfer-weighted (APTw) magnetic resonance imaging (MRI), and to perform a preliminary evaluation of APTw imaging in response assessment. METHODS: Sixteen patients with NPC planned for treatment with radiotherapy and/or chemotherapy underwent APTw imaging of the primary tumour pre-treatment and 2-week intra-treatment. Difference in pre- and intra-treatment APT mean (APT(mean)) was compared using the Wilcoxon signed rank test. Differences in APT(mean) and percentage change (%Delta) in APT(mean) were compared between responders and non-responders based on the outcome at 6 months, using the Mann-Whitney U test. RESULTS: APT(mean) decreased in 9/16 (56.3%) and increased in 7/16 (43.7%) with no significant difference between the pre- and intra-treatment APT values for the whole group (p > 0.05). NPC showed response in 11/16 (68.8%) and non-response in 5/11 (31.2%). There were significant differences between the %Delta of responders and non-responders for APT(mean) (p = 0.01). Responders showed %Delta decrease in APT(mean) of - 23.12% while non-responders showed a %Delta increase in APT(mean) of + 102.28%. CONCLUSION: APT value changes can be detected in early intra-treatment. Intra-treatment %Delta APT(mean) shows potential in predicting short-term outcome.