Selected study-related factors that may bias the estimated risk of second malignancies after multiple myeloma
| Short-term follow-up |
| Small sample sizes |
| Combinations and interactions between multiple drugs |
| Inadequate control group |
| Retrospective data collection |
| Under-reporting by clinicians |
| Survival difference (person-years) between experimental and surveillance arms |
| Short-term follow-up |
| Small sample sizes |
| Combinations and interactions between multiple drugs |
| Inadequate control group |
| Retrospective data collection |
| Under-reporting by clinicians |
| Survival difference (person-years) between experimental and surveillance arms |