trials bias oncology expectation bias

What is the weight of expectation bias in oncology trials?

by Cinzia Dello Russo, Pierluigi Navarra

Feb 11^th 2023
3 mins
BJCP: Volume 89, Issue 4 April 2023, Pages 1279-1281

Share This Article

Summary

Expectation bias, also known as the Rosenthal effect, can distort experiment results due to the expectations of investigators or patients.
Blinding or masking treatments is a classical method to reduce expectation bias in biomedical research.
Expectation bias is considered an important confound in oncology studies, necessitating a blinded independent review for accurate interpretation of outcomes.
FDA and EMA guidelines recommend independent blinded reviews for several endpoints in cancer trials, though the FDA allows for case-by-case decisions regarding some endpoints.
Studies show no significant difference between local assessments (LAs) and blinded independent central reviews (BICRs) of progression-free survival (PFS) in phase-3 trials, suggesting investigator expectation does not influence PFS results.
However, in phase-2 trials, local investigators tend to overestimate the overall response rate (ORR) compared to BICR, indicating expectation bias can affect ORR assessments in uncontrolled trials.
Methodological differences, such as the number of assessments and time-to-response, might account for discrepancies between ORR and PFS measurements.
In conclusion:
- Expectation bias does not influence PFS results in phase-2 or phase-3 studies.
- No significant differences in ORR assessments between LAs and BICRs are found in controlled trials.
- Significant concern exists for ORR assessment in single-group nonrandomized phase-2 trials due to notable discrepancies between LAs and BICRs.

In biomedical research, expectation bias, also referred to as Rosenthal effect, is the distorting effect on the results of an experiment caused by the expectation that the investigator, or the patient, has about the results themselves. The classical way to reduce the influence of this bias on the interpretation of results is through the blinding, or masking, of treatments, both terms referring to keeping the patients, the investigators, or the assessors unaware of the assigned treatment...

Click for Source Download PDF version

trials, bias, oncology, expectation bias