Dosimetry and efficacy of high intensity focused ultrasound in the treatment of pancreatic cancer

Abstract

Objective To study the efficacy and the safe dosage of high intensity focused ultrasound (HIFU) ablation in pancreatic cancer.Methods From November 2010 to May 2013,21 patients with advanced pancreatic cancer were treated by HIFU at the First Affiliated Hospital of Zhengzhou University.These patients who were randomly divided into two groups (10 and 11 patients respectively),were given a low-power (100～249 W) treatment and a high power (250 ～350 W) treatment.These two groups of 21 patients received a total of 25 times of HIFU treatment (3 patients received twice of low-power treatment,while 1 patient received twice of high-power treatment).The two groups were compared by analyzing the treatment parameters (average power,total treatment time,treatment total energy,treatment volume,etc.) and volume of tumour response as shown on postoperative imaging (CT or MRI) examinations.Also,the complications,degree of pain relief and survival were compared.The energy efficiency factor (EEF) and the ablation ratio were calculated.A preliminary study was conducted on the relationship of the ultrasound dose and the ablation effect of HIFU treatment for pancreatic cancer.Results (1) The EEF of the high-power group (≥250 W) and the low-power group (＜ 250 W) were (10.39 ± 5.71) J/mm3 and (21.62 ± 9.81) J/mm3,the former group was significantly lower than the latter group (P ＜0.05) ; the ablation ratio of the high-power group was higher than the low-power group,(91.52 ± 4.18)％ versus (51.59 ± 7.66)％ respectively,the difference was statistically significant (P ＜ 0.001).(2) The efficiency factor and the ablation volume for the HIFU treatment showed a linear trend,and both were negatively correlated (Pearson correlation coefficient r =-0.485,P ＜ 0.05).(3) There was no serious complication after the HIFU treatment.In the low-power group,six of ten patients were alleviated of his pain (60％) ; the CA19-9 decreased in four of ten patients after HIFU treatment (40％).In the high-power group,nine of eleven patients were significantly relieved of pain after treatment (82％),the CA19-9 decreased in five of nine patients after HIFU treatment (56％).(4) On Kaplan-Meier survival analysis,HIFU treatment of patients with pancreatic cancer,the median survival was 8 months and 9 months in the low-power group and high power group,respectively (Log-rank test x2 =0.05,P =0.944).Conclusion During HIFU treatment of patients with pancreatic cancer,if the ultrasound power was between 250 W and 350 W,there was a higher proportion of tumor ablation,but with no serious complications.Thus,this dose was safe. Key words: Pancreatic cancer; Ultrasound, high-intensity focused, transrectal; Dosimetry