Does a drug do better when it is new?

Background: When assessing a new, promising therapeutic approach, a clinician's perception of a drug's effectiveness may be shaped by different kinds of phenomena, and among them, a favorable attitude towards new treatments, and as a result a tendency to overestimate their efficacy (wish bias). Materials and methods: A retrospective study of published randomized clinical trials of doxorubicin-based chemotherapy for advanced breast cancer was carried out. Global (complete plus partial) response rate over time with allowance for type of drug regimen (mono- or polychemotherapy) and prior adjuvant therapies was assessed in the doxorubicin-containing arm using multivariate logistic regression analysis. Results: Twenty-nine studies published from 1975 to 1999 were retrieved for a total of 2234 women with advanced breast cancer enrolled in the doxorubicin-containing arms. There was a significant decrease in response rate to doxorubicin as first-line treatment over time that resisted adjustment for important differences in therapeutic management [odds ratio for global response = 0.89, 95% confidence interval (CI) 0.81 to 0.99]. Conclusions: Although only one drug (doxorubicin) in one clinical context (advanced breast cancer) has been analyzed, our findings support the use of double blind methodology whenever possible when assessing subjective endpoints and encourage further studies aimed at defining the clinical relevance of a wish bias in medicine.