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Duration of treatment in oncology clinical trials: does the duration change when the same drug moves from the experimental arm to the control arm?



When a new drug comes to the market, the incentive for the sponsoring company is to maximize the treatment duration in order for the patient to reap the full therapeutic benefit of the product and achieve a positive trial result. We sought to enumerate instances when an already-approved oncology drug was used as a comparator for a newer drug seeking approval and compare the duration of treatment when it is used in the intervention arm to when it is used as a comparator.

Patients and methods

In a cross-sectional analysis, we searched drug approval announcements for advanced, metastatic, or unresectable cancers between 2009 and 2020. We included studies reporting on an approved drug and studies reporting on when the same drug was used as a comparator for other drugs seeking Food and Drug Administration (FDA) approval. We examined median progression-free survival and duration of treatment for when the drug was initially approved and for when the drug was used as a comparator for other drugs that were seeking approval.


Of the 23 instances when an approved drug was later used as a comparator against a newer drug seeking FDA approval, we found 11 instances (47.8%) where the drug, when used as a comparator arm, had a shorter duration of treatment than when it was used in the intervention arm. The median duration of treatment in the study initially testing the drug was 6.0 months (range: 2.2-12.7 months), whereas the median duration of treatment when the same drug was used as a comparator was 4.9 months (range: 1.7-12.0 months).


These results suggest that there is bias in how long a patient receives a given therapy, and this bias favors the newer therapy. Clinical trialists should seek to utilize methodology that reduces bias so that the relative efficacy of newer drugs can be objectively assessed.

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