Patient preferences and predicted relative uptake for targeted therapies in metastatic colorectal cancer: a discrete choice experiment

Objective Ras wild-type metastatic colorectal cancers (mCRC) may be treated with anti-vascular endothelial growth factor (VEGF) or anti-epidermal growth factor receptor (EGFR) agents. We aim to estimate patients' preferences for mCRC treatment and relative importance of cost, efficacy improvement, avoidance of side effects and therapy convenience, and relative uptake between profiles that resemble Bevacizumab (anti-VEGF) and Cetuximab (anti-EGFR), two commonly prescribed mCRC targeted therapies. Methods Discrete choice experiment (DCE) was administered to English- or Chinese-speaking Stage 2 or 3 colon cancer patients at the National Cancer Centre Singapore. DCE attributes comprise progression-free survival (PFS), severity of acne-like skin rashes, severity of bleeding, out-of-pocket cost per month and frequency of drug administration. Mixed logit model was used to calculate preference weights for all attribute levels. Subgroup analyses were conducted by interacting attribute levels with selected respondent characteristics. Relative uptake rates for various medication scenarios were studied. Results 169 respondents aged 61.5 +/- 10.5 years completed the survey. They placed the greatest weight on cost, followed by bleeding and skin rashes, then PFS and finally frequency of drug administration. This was similarly observed in the subgroup analyses. A scenario with shorter PFS but less severe side effects has a slightly higher relative uptake at 55%. One quarter of respondents reported that they would not take the treatment they preferred in the choice task. Conclusion Patients were willing to trade off some degree of efficacy to avoid certain severity of side effects. It is therefore crucial for patients and physicians to discuss patients' preferences and circumstances to understand which attributes are more important, as well as patients' views on the trade-offs between treatment benefits and risks.