The Application Of The Low-dose Volume Perfusion CT Follow-up Mode In Advanced Lung Adenocarcinoma Patients With EGFR-TKI Treatment Follow-up

Objective:Explore the application value of the low-dose volume perfusion CT (volume perfusion computer tomography, VPCT) follow-up mode to reduce the CT radiation dose of followed-up patients with advanced lung adenocarcinoma after gefitinib therapy.Methods:Collected20patients of advanced lung adenocarcinoma with epidermal growth factor receptor (Epidermal growth factor receptor, EGFR) mutation from April2010to January2012in Xiangya Hospital Central South University, and all patients underwent VPCT (80kV,100mAs, the TST42s, ISD1sX30+3SX4total number of scans of34) before gefitinib treatment as the basic scan, according to different total scan time (total scan time, TST) and delayed inter-scan time (Inter-scan delay, ISD) to design various post-processing modes in order to observe the blood flow (blood flow, BF) changes of lung lesions, and select appropriate TST and ISD to decrease the total scan frequency of VPCT every time in the follow-up, thereby reducing the radiation dose.20patients with gefitinib treatment every2cycles (6weeks) were followed up according to the designed low dose VPCT model, and observed the changes in tumor BF value.The rise of tumor BF value in gefitinib treatment process was regarded as standard for the judgment of pathological process, compared to Response Evaluation Criteria in Solid tumors(RECIST), use progress free survival(PFS) as the indicator for the mid-term outcome evaluation, and observe the effects of low dose VPCT follow-up mode for the efficacy of gefitinib treatment.Result:(1) Identify the low dose VPCT follow-up mode:a) When scan time was constant, the effect of delaying and prolonging scan interval time on tumor BF value:TST was42s, ISD every3seconds longer, BF increased8%; b) When delayed interval scan time was constant, the effect of reducing the total scan time on tumor BF value:ISD was3s,shorten TST to30seconds, BF value had no significant change; c) When the total scanning time was shortened to30s, ISD extended from3s to4s, BF had no significant change; d) Synthesize the results from a to c to set the low dose VPCT follow-up mode, and the dose of low dose VPCT follow-up mode (80KV,100mAs, TST30s, One second+ISD4sX7, the total number of scans was8) was23.5%(8/34) of the normal mode (80KV,100mAs, TST42s, ISD1sX30+3sX4, the total number of scans was34).(2) Evaluation of the efficacy of gefitinib by the low dose VPCT follow-up mode:the PFS measured by low dose VPCT follow-up mode (VPCT-PFS) compared with that measured by RECIST criteria (RECIST-PFS) was positively correlated (r=0.761, p=0.004), VPCT-PFS was shorter than RECIST-PFS (median PFS was12weeks vs.30weeks), the median leading time was18weeks. Low-dose VPCT follow-up mode predicted the recurrence of sensitivity, specificity, accuracy, positive predictive value and negative predictive value were92.3%,60.0%,83.3%,85.7%and75.0%, respectively.Conclusion:The low-dose VPCT follow-up mode can effectively reduce the radiation dose of advanced lung adenocarcinoma patients with EGFR-TKI treatment in the follow-up, and accurately determine the efficacy.