Table 4. Reasons and strategies for trial redesign.
| Characteristics of trials with major redesign (n = 27) | Frequency of redesigned trial characteristic by accrual status at trial closure | |
|---|---|---|
|
| ||
| Sufficient | Insufficient | |
| Primary reason for redesign | ||
| Slow accrual | 3 | 4 |
| Fast accrual | 3 | 0 |
| New data | 6 | 1 |
| Lower than predicted event rate | 3 | 1 |
| Interim analysis results | 1 | 0 |
| Different than anticipated trial coursea | 4 | 0 |
| Unknown | 0 | 1 |
| Accrual status at time of redesign | ||
| Slower than projected | 5 | 7 |
| On projected target | 10 | 0 |
| Faster than projected | 5 | 0 |
| Primary redesign strategyb | ||
| Decrease sample size | 2 | 1 |
| Increase sample size | 13 | 0 |
| Alter endpoint | 1 | 0 |
| Recalculate type 1 error from two- to one-sided | 1 | 0 |
| Modify eligibility criteria | 0 | 2 |
| Add/delete treatment arm | 3 | 1 |
| Modify treatment arm | 0 | 1 |
| Change randomization to 2:1 | 0 | 1 |
a
Includes different than anticipated treatment effects, treatment compliance, patient eligibility, or cooperative group participation.
b
One trial not included here closed and reopened as a different trial as a response to poor accrual.