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

Abstract

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.

Keywords:

• Targeted therapy
• metastatic colorectal cancer
• discrete choice experiment
• patient preferences
• relative uptake

Transparency

Declaration of funding

This work was supported by the Singapore Cancer Society Cancer Research Grant titled “Health Preferences of Colorectal Patients in Singapore”, which was awarded in 2014. The study sponsor had no role in the study design, collection, analysis and interpretation of data; in the writing of the manuscript; and in the decision to submit the manuscript for publication.

Declaration of financial/other relationships

There are no relationships to be declared. Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Author contributions

XYW: study conception and design, data analysis and interpretation, manuscript drafting and revision; AQJL: data collection, analysis and interpretation; QYS: data, collection, analysis and interpretation; JWKC: study conception and design, manuscript revision; MHC: study conception and design, manuscript revision; WST: study conception and design, manuscript revision; HLW: study conception and design, data interpretation and manuscript revision. All authors gave the final approval of the version to be published and agreed to be accountable for all aspects of the work.

Acknowledgements

We thank A/Prof Lita Chew (Department of Pharmacy, National Cancer Centre Singapore [NCCS]) for providing valuable insights and direction during the study conception phase. We thank the attending physicians and clinic staff at NCCS Clinic D for their kind assistance during study recruitment. We also thank Dr Swee Sung Soon, Mr Keegan Lin and Ms Janie Lim for their contribution in research administration and Phase 1 data collection (funded by “Health Preferences of Colorectal Patients in Singapore”) and Ms Joy Yau and Ms Isy Yu for their assistance in patient screening and data collection in Phase 3. They were funded by indirect research costs (cumulative from various grants awarded to Dr Hwee-Lin Wee).