Development and validation of an Emoji Sticker Scale from the Patient-Reported Outcome Common Terminology Criteria for Adverse Events for patients with breast cancer

Purpose: Emojis are commonly used for daily communication and may be useful in assessing patient-reported outcomes (PROs) in breast cancer. The purpose of this study is to develop and validate an Emoji Sticker Scale (ESS) as a new PRO measurement. Methods: : Eighteen original ESS items were developed from the PRO-CTCAE. In cohort one, the ESS validity and reliability were examined in patients with breast cancer, using a semi-structured five-question survey to investigate content validity. PROs with PRO-CTCAE and ESS were examined twice to determine criteria validity and test-retest reliability. In cohort two, the responsiveness of the scales were examined in patients treated with anthracycline, docetaxel, paclitaxel, and endocrine therapy. PROs with PRO-CTCAE and ESS were investigated two or three times, depending on the therapy. Results: : Patients were enrolled from August 2019 to October 2020. In cohort one (n=70), most patients had no difficulties with the ESS, but 16 patients indicated that it was difficult to understand severities in the ESS. For criterion validity, Spearman rank correlation coefficients (r s ) between PRO-CTCAE and ESS items were ≥0.41, except for “Decreased appetite.” For test-retest reliability, κ coefficients of the ESS were ≥0.41 for 16/18 items (88.9%). Response time was significantly shorter for the ESS than for PRO-CTCAE ( p <0.001). In cohort two (n=106), score changes between PRO-CTCAE and ESS for relevant symptoms all had correlations with r s ≥0.41. Conclusion: Parts of the original ESS developed from PRO-CTCAE require updating. However, this study provides a comprehensive confirmation of the validity, reliability, and responsiveness of the ESS.