CT perfusion in predicting treatment response of nasopharyngeal carcinoma

Abstract

Background: Direct nasopharyngoscope with biopsy is the gold standard for assessing tumor response of nasopharyngeal carcinoma (NPC). It is invasive with risk of hemorrhage or infection. Objective: Explore the usefulness of pre-treatment CT perfusion (CTP) and clarify the parameters in predicting the treatment response. Material and Method: Twelve patients with histologically proven NPC who underwent pretreatment contrast enhanced CT (CECT) and CTP with parameters (blood flow (BF), blood volume (BV) and permeability), followed by CECT at three months after complete concurrent chemo-radiotherapy or radiotherapy were included in this prospective, cross-sectional study. Pre- and post-treatment primary tumor volumes based on free hand drawn region encompassing the entire primary tumor were measured and compared. The response to therapy was also assessed by RECIST guideline version 1.1, based on sum of the diameters of longest diameter for primary tumor and minimal transverse diameter for nodal lesions for all target lesions on the pre- and post-treatment imaging, and classified into "Non-response" group and "Complete response" group. Statistical analysis was performed using Pearson's correlation coefficients and Mann-Whitney U test. Results: Ten and two patients (83.3%, 16.7%) belonged to "Complete response" and "Non-response" groups respectively. Elevated permeability, BF and BV had a following trend of positive correlation with degree of primary tumor volume reduction without statistical significance. The values of permeability, BF, and BV had a trend to be higher in "Complete response" group compared with "Non-response" group (p = 0.053, 0.390 and 0.519 respectively). The permeability had the highest predictive value with an area under the ROC curve of 0.95 and cutoff value of 45 ml/100 g/min (sensitivity, 100%; specificity, 90%). Conclusion: Pre-treatment CTP can be useful non-invasive tool in predicting treatment response of NPC. Permeability is the excellent parameter used to differentiate between complete and non-response groups.