Role of perfusion CT in the evaluation of functional primary tumour response after radiochemotherapy in head and neck cancer: Preliminary findings

Objective: To report the initial results of a prospective study aimed at evaluating the CT perfusion parameter changes (ΔPCTp) of the primary tumour after radiochemotherapy (RCT) in head and neck cancer (HNC) and to correlate with positron emission tomography (PET)/CT response. Methods: Eligibility criteria included HNC (Stage III-IV) candidates for RCT. Patients underwent perfusion CT (PCT) at baseline and at 3 weeks and 3 months after treatment. Blood volume, blood flow, mean transit time (MTT) and permeability surface (PS) product were computed. Moreover, PET/CT was performed at baseline and 3 months after treatment. The ΔPCTp were evaluated between baseline and 3-week/3-month evaluations, whereas PET/CT response was based on the maximum standardized uptake value changes according to the European Organization for Research and Treatment of Cancer criteria. Results: Between July 2012 and July 2015, 25 patients were enrolled. A significant reduction of all CT tumour perfusion parameters (PCTp) was observed from the baseline to after RCT (p<0.001). Specifically, a significant reduction was shown at 3 weeks for all PCTp except MTT (from 6.18 to 5.14s; p=0.722). Differently, a significant reduction of all PCTp (p<0.001) including MTT (from 6.18 to 2.24s; p=0.001) was shown at 3 months. Moreover, the reduction of PS resulted in a significant prediction of PET/CT response at 3 months (p=0.037) with the trend also at 3 weeks (p=0.099) at the multivariate analysis. Conclusion: Our preliminary findings seem to show that almost all PCTp are significantly reduced after RCT, whereas PS seems to come out as the strongest factor in predicting the PET/CT response. Advances in knowledge: This article provides information on the potential useful role of PCT in evaluating tumour response after both early and late RCT.