Sample size calculations for different predicted PTM rates
| Control group As needed radiotherapy | ||||||
|---|---|---|---|---|---|---|
| Intervention group Prophylactic radiotherapy | 90% power (α 0.05, 3% loss to FU) | 80% power (α 0.05, 3% loss to FU) | ||||
| Incidence of PTM at 12 months (%) | 12 | 15 | 18 | 12 | 15 | 18 |
| 1 | 203 | 150 | 118 | 153 | 112 | 88 |
| 2 | 269 | 185 | 140 | 201 | 140 | 105 |
| 3 | 357 | 234 | 169 | 266 | 174 | 125 |
| 4 | 482 | 294 | 203 | 360 | 220 | 152 |
| 5 | 670 | 375 | 248 | 500 | 281 | 184 |
All rates include a projected 3% loss to follow-up. The figures in the shaded cells are those which are achievable within the proposed sample size.
FU, follow up; PTM, procedure tract metastasis.