Figure 6

Abdominal FLASH irradiation has similar tumor control efficacy as CONV irradiation and spares intestinal function in a preclinical syngeneic ovarian cancer mouse model. (a) Relative body weight (%) of ID8 tumor-bearing mice over time after 14 Gy CONV or FLASH TAI. Bold lines show the average for each cohort. The dotted lines indicate days at which the difference between CONV and FLASH is significant. n = 16 per group. (b) Representative images of stool pellets (left) and quantification of the number of stool pellets (right) excreted over 24 h at 15 days after tumor cell injection, or 5 days after 14 Gy abdominal irradiation (n = 16 mice per group), showing increased stools after FLASH vs. CONV irradiation, consistent with the observation in non-tumor bearing mice. (c) Representative images displaying metastatic tumor burden in mice that were intraperitoneally injected with ID8 ovarian tumor cells and (d,e) quantification of the number of solid tumor nodules (d) and total tumor weights (e) in control mice and mice irradiated with 14 Gy CONV or FLASH irradiation, demonstrating similar tumor control efficacy with both FLASH and CONV irradiation. n = 8 mice per group; ns no significant difference, *p < 0.05, **p < 0.01; Comparisons by one-way ANOVA followed by Tukey’s multiple comparisons test. Error bars represent standard deviation of the mean. (f) Representative γ-H2AX (red), TROMA-1 (green, a marker if ovarian cancer cells) and DAPI (blue) stained images of tumors from ID8 ovarian tumor bearing mice at the indicated time points after sham or sublethal 14 Gy abdominal irradiation. (g) Quantification of the average number of γ-H2AX + foci per TROMA-1 positive ID8 cancer cell 4 h, 12 h and 24 h after 14 Gy abdominal irradiation. n = 4 mice per group. An average of 15 TROMA-1 positive cancer cells per mouse were quantified for γ-H2AX foci. At 4 and 12 h after irradiation, γ-H2AX foci in CBCs were similar after FLASH and CONV irradiation and resolved to baseline levels in both groups by 24 h. ns no significant difference, *p < 0.05, **p < 0.01, ***p < 0.001; Unirradiated control versus CONV or FLASH compared by one-way ANOVA followed by Tukey’s multiple comparisons test. Error bars represent standard deviation of the mean.