Meta-analysis of adverse event rates in 15 North Central Cancer Treatment Group phase II metastatic breast cancer clinical trials for the development of adverse event stopping rules.
Authors: Tenner KS , Dueck AC , Hillman DW , Rowland KM , Palmieri FM , Suman VJ , Perez EA 
Published: December 2010

Abstract #6149

Background: Internal Review Boards and Data and Safety Monitoring Boards often require protocol-specified adverse event (AE) stopping rules for safety monitoring. However, availability of safety data for investigational agent(s) may be limited at the time of protocol development in the phase II setting. This meta-analysis was undertaken to quantify the variability of AE rates in North Central Cancer Treatment Group (NCCTG) phase II metastatic breast cancer (MBC) clinical trials and to investigate whether study factors are associated with AE rates for the development of AE stopping rules in future phase II clinical trials.&#x2028; Methods: All closed NCCTG phase II MBC clinical trials using CTC v2.0 or CTCAE v3.0 for AE monitoring were selected. Rates of G3/4 AEs (overall, hematologic [H], and non-hematologic [NH]) and of study discontinuation [SD] due to AEs were calculated for each trial. Associations between study factors [number of agents (single vs combination); line of therapy (first-line only vs other); and type of therapy (chemotherapy vs other)] and AE rates were assessed via Wilcoxon rank sum tests.&#x2028; Results: 15 trials met inclusion criteria. 7 used CTCAE v3.0; 6 investigated single agents; 5 investigated first-line therapy; and 11 investigated chemotherapy regimens. 694 pts were evaluable for AE analysis. The G3/4 AE rate across trials was 68% (16-98%) overall, 45% (0-96%) H, and 51% (16-78%) NH. The overall rate of SD due to AEs was 13% (0-40%). The overall rate of G3/4 AEs was significantly lower in single agents vs combination regimens (30% vs 86%, p=0.004). This association held for H (2% vs 66%, p&lt;0.0001) and NH (27% vs 57%, p=0.03) Aes. The rate of SD due to AEs was also significantly lower in single agents vs combination regimens (0.5% vs 15%, p=0.04). The rate of G3/4 AEs was significantly higher in first-line only trials vs other trials (overall: 90% vs 47%, p=0.04; H: 73% vs 5%, p=0.02; NH: 66% vs 41%, p=0.08). The rate of SD due to AEs was also significantly higher in first-line only trials (18% vs 4%, p=0.008). The only significant association with chemotherapy vs other therapy was G3/4 H AE rates (51% vs 2%, p=0.02).&#x2028; Discussion: High variability in G3/4 AE rates overall and in H and NH AEs was noted in these 15 trials. There is also high variability in the rates of SD due to AEs. The data suggest that clinical trials with single agent regimens have lower AE rates than combination regimens and, surprisingly, trials of first-line therapy only have higher AE rates than other trials. This may be due to more aggressive therapy being tested in the first-line setting. Although data from previous trials with the investigational agent(s) should be used for developing AE stopping rules when available, this study suggests that study factors such as number of agents and line of therapy can be useful when previous data are limited.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6149.