Table 1.
Summary of dose escalation studies.
| Dose level | Number of fractions | Dose per fraction (Gy) | Total Dose (Gy) | BED α/β = 3 | BED α/β = 10 | Elapsed days | Days of treatment | Field size | Strain | Incidence of severe toxicity/death | Death post SART (weeks) | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Male | Female | |||||||||||
| DL1 | 1 | 15 | 15 | 90 | 38 | N/A | 1 | 2 cm | C57Bl/6 | 0 of 3 | ||
| 2 | 10.2 | 20.4 | 90 | 41 | 8 | 1,8 | 2 cm | C57Bl/6 | 0 of 3 | |||
| 3 | 8.1 | 24.3 | 90 | 44 | 9 | 1,5,9 | 2 cm | C57Bl/6 | 0 of 3 | |||
| 5 | 6 | 30 | 90 | 48 | 9 | 1,3,5,7,9 | 2 cm | C57Bl/6 | 0 of 3 | 0 of 3 | ||
| DL2 | 1 | 18.3 | 18.3 | 130 | 52 | N/A | 1 | 2 cm | C57Bl/6 | 0 of 3 | ||
| 2 | 12.6 | 25.2 | 131 | 57 | 8 | 1,8 | 2 cm | C57Bl/6 | 0 of 3 | |||
| 3 | 10 | 30 | 130 | 60 | 9 | 1,5,9 | 2 cm | C57Bl/6 | 0 of 3 | |||
| 5 | 7.5 | 37.5 | 131 | 66 | 9 | 1,3,5,7,9 | 2 cm | C57Bl/6 | 0 of 3 | 1 of 3 | 16 | |
| 5 | 7.5 | 37.5 | 131 | 66 | 5 | 1,2,3,4,5 | 2 cm | C57Bl/6 | 1 of 5 | 3 of 5 | 12–16 | |
| 5 | 7.5 | 37.5 | 131 | 66 | 9 | 1,3,5,7,9 | 2 cm | CD-1 | 0 of 6 | |||
| 5 | 7.5 | 37.5 | 131 | 66 | 9 | 1,3,5,7,9 | 1 cm (pelvis) | CD-1 | 0 of 6 | |||
| 5 | 7.5 | 37.5 | 131 | 66 | 9 | 1,3,5,7,9 | 1 cm (low abd) | C57Bl/6 | 1 of 4 | 14 | ||
| DL3 | 1 | 21.8 | 21.8 | 180 | 69 | N/A | 1 | 2 cm | C57Bl/6 | 0 of 2 | ||
| 2 | 15 | 30 | 180 | 75 | 8 | 1,8 | 2 cm | C57Bl/6 | 0 of 3 | |||
| 3 | 12 | 36 | 180 | 79 | 9 | 1,5,9 | 2 cm | C57Bl/6 | 0 of 3 | |||
| 5 | 9 | 45 | 180 | 86 | 9 | 1,3,5,7,9 | 2 cm | C57Bl/6 | 1 of 3 | 2 of 3 | 7–12 | |
| 5 | 9 | 45 | 180 | 86 | 9 | 1,3,5,7,9 | 1 cm (pelvis) | C57Bl/6 | 0 of 4 | |||
| 5 | 9 | 45 | 180 | 86 | 9 | 1,3,5,7,9 | 1 cm (low abd) | C57Bl/6 | 2 of 4 | 9–10 | ||
| DL4 | 2 | 18 | 36 | 252 | 101 | 8 | 1,8 | 2 cm | C57Bl/6 | 0 of 3 | ||
| 3 | 14.4 | 43.2 | 251 | 105 | 9 | 1,5,9 | 2 cm | C57Bl/6 | 3 of 3 | 14–17 | ||
| 5 | 10.9 | 54.5 | 253 | 114 | 9 | 1,3,5,7,9 | 2 cm | C57Bl/6 | 3 of 3 | 5 | ||
Dose levels and fractionation schemes evaluated in the pelvic stereotactic ablative radiotherapy (SART) dose escalation studies are shown, including number of fractions, dose per fraction, cumulative nominal dose, BED, days on which radiation was delivered, diameter of the circular radiation field, mouse strain, and incidence/timing of severe toxicity or death occurring within 6 months of treatment. Some cohorts were monitored longer than 6 months. No treatment-related deaths occurred in these cohorts. Elapsed days is the total number of days over which radiation was delivered, including the first and last day. Radiation fractions were equally distributed across the elapsed days. The single fraction regimen at DL4 was not evaluated because the length of time in the restrainer would have exceeded the maximum time approved under our animal protocol. The 2 cm radiation field was centered in the pelvis over the prostate and/or bladder (see “Methods” for details). The 1 cm radiation field covered either the lower half (pelvis) or upper half (low abdomen) of the 2 cm field. BED and α/β are further described in the “Methods”.
DL dose level, α/β alpha-beta ratio, BED biologic effective dose, N/A not applicable.