To explore the effect of diagnostic ultrasound combined with microbubbles on tumor growth, metastasis rate, and animal survival in rabbits bearing VX2 tumors undergoing chemotherapy.

Forty-one male rabbits bearing subcutaneous VX2 tumors from Laboratory Animal Center, Xinqiao Hospital, The Army Medical University were randomized into three groups: A (n=14), B (n=14), and C (n=13). All animals were given an intravenous administration of doxorubicin at 1 mg/kg. Animals in group A were additionally treated by high mechanical index (0.7-0.8) ultrasound combined with microbubbles (HUSM), group B was treated by low mechanical index (0.2-0.3) ultrasound combined with microbubbles (LUSM), and group C was treated by sham ultrasound. All the groups were treated every other day for a total of three times. The longest diameter and shortest diameter of the tumor were measured at 1 d, 3 d, 5 d, 8 d, 11 d, 14 d, 17 d, 20 d, 23 d, 26 d, 29 d, and 32 d to calculate tumor volume and plot tumor growth curve, which was compared by repeated measures analysis variance. At the end of the study, the multi-organ metastasis rate and survival time of rabbits were observed and compared by χ² test and one-way ANOVA, respectively.

After treatment, the tumor growth trend in group B was significantly lower than that of group C (P=0.031), but there was no statistically significant difference between groups A and C and between groups A and B (P＞0.05). The mean survival time of rabbits in groups A, B, and C was (100.00±29.61) days, (94.92±36.92) days, and (118.92±48.41) days, respectively; there was no significant difference among them (F=1.146, P=0.255). Six (42.90%), four (28.60%), and six (46.20%) rabbits developed multi-organ metastasis in groups A, B, and C, respectively; the effect of different treatments on distant metastasis rate had no significant difference (χ²=1.007, P=0.604).

LUSM can enhance chemotherapy effects and inhibit tumor growth while not promoting multi-organ metastasis or shortening the survival of rabbits.