Effect of Crossover in Oncology Clinical Trials on Evidence Levels in Early Benefit Assessment in Germany

BACKGROUND

In oncology clinical trials, crossover is used frequently but may lead to uncertainties regarding treatment effects.

OBJECTIVE

To investigate the handling of evidence from crossover trials by the European Medicines Agency (EMA) and the German Federal Joint Committee (G-BA).

METHODS

For oncology medicines with early benefit assessments before January 2015, presence of crossover, clinical data, EMA requests for additional data, and G-BA benefit ratings/evidence levels were analyzed from manufacturers' dossiers, G-BA appraisals, European Public Assessment Reports, and original publications.

RESULTS

Eleven of 21 benefit assessments included crossover trials. Significant intergroup differences (P < 0.05) in overall survival (OS) were noted in 7 of 11 trials with and 7 of 10 without crossover. For 6 of 11 medicines with crossover, these were demonstrated before crossover. Treatment effects generally worsened with increasing proportions of crossover. The EMA requested additional data more frequently if crossover was performed, particularly if no OS data were available before crossover. The G-BA granted a considerable benefit to 73% of medicines with crossover and 40% of those without. Evidence levels were intermediate for 50% and 75%, respectively. None of the medicines received the highest evidence level.

CONCLUSIONS

In G-BA appraisals, oncology medicines with crossover received better additional benefit ratings, but were assigned lower evidence levels, than those without. The five medicines with crossover after progression were assigned lower evidence levels than the six medicines with crossover after demonstration of superior OS, indicating that the way in which crossover is implemented may be one factor influencing the assignment of evidence levels by the G-BA.

Randomised controlled trials in oncology closed early for benefit: trends in methodology, results, and interpretation

PURPOSE

To assess methodology, results and interpretation of oncology randomised controlled trials closed early for benefit (RCTCEB).

METHODS

Structured literature search (1950-2008) to identify all published oncology RCTCEB. We then searched for related follow-up articles and conference abstracts to evaluate whether study results and conclusions changed with longer follow-up. A standardised data abstraction process captured information related to statistical methodology, details of interim analyses, results and conclusions. Original articles and follow-up reports were compared for results of primary end-point and author conclusions.

RESULTS

We identified 71 RCTCEB. In 16 articles (23%) the study primary end-point was not explicitly stated. Most trials were open to accrual (47/71, 66%) at the time of closure. Formal interim analysis was performed in 65 (92%) trials of which 72% (47/65) was reported as planned; 82% (53/65) reported stopping rules. Trials on average accrued 75% of the planned sample size. Amongst the 23 (32%) RCTCEB with follow-up reports, in only one case did the study results or conclusions change substantially.

CONCLUSIONS

While the majority of oncology RCTCEB follows rigourous methodological principles, an important percentage includes limitations in design and/or analysis. Amongst the 23 studies with subsequent follow-up reports, initial results were confirmed in 22 (96%).