Consent Form Heterogeneity in Cancer Trials: The Cooperative Group and Institutional Review Board Gap

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Cooperative group (CG) provided consent forms (CGP-CFs) undergo re-review and revision by local institutional review boards (IRB) before institutional approval. We compared the relative readability and length of IRB-approved consent forms (IRB-CFs) used at seven academic institutions with their corresponding CGP-CFs. We also assessed the variability of these metrics across our institutions.


This study included 197 consent forms (CFs) from 56 CG trials that were open in at least two of the participating institutions. The Flesch Reading Ease Score (FRES), the Flesch–Kincaid Grade Level (FKGL), and document length were collected on all CFs. Unpaired t test was used to compare length and readability of CGP-CF with the IRB-CF. Analysis of variance and Bonferroni-Dunn tests were used to assess interinstitutional variability in readability for all IRB-CFs. All statistical tests were two-sided.


IRB-CFs were statistically significantly longer than CGP-CFs (mean number of pages = 17 vs 13; P < .001). Mean FKGLs were higher (10.3 vs 9.4; P < .0001) and the mean FRESs were lower (53.1 vs 57.1; P < .0001) for IRB-CFs compared with CGP-CFs. Readability varied statistically significantly between institutions for all sections of the IRB-CF (P < .0001). Finalized IRB-CFs for identical clinical trials at different institutions demonstrated substantial heterogeneity of readability and length.


As CFs progress from National Cancer Institute (NCI)–sponsored CGs to local IRBs, they seem to become longer and less readable. Interinstitutional heterogeneity in CF readability is substantial and widespread. More consistent adherence to CGP-CFs based on the newly revised NCI CF template with minimal modification by local IRBs should help simplify and standardize CFs used in cancer clinical trials.

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