Measuring chronic myeloid leukaemia TKI-related toxic effects in the real world: a systematic review and critical assessment of content validity of patient-reported outcome measures

Insight into real-world treatment-related toxic effects reported by patients has the potential to improve care, benchmark trials, and fill knowledge gaps, especially in patients with chronic myeloid leukaemia, which is treated in the majority of patients continually with tyrosine-kinase inhibitors (TKIs). The aim of our systematic review was to investigate the content validity of instruments that elicit TKI-related toxic effects reported by patients with chronic myeloid leukaemia in the real world. We searched PubMed and Embase from Jan 1, 2017 to Oct 21, 2022. Studies on instruments used in or developed for patients with chronic myeloid leukaemia that assess a patient's symptoms were eligible. Content validity was assessed according to the Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN): none of the six identified instruments were rated as sufficient. Five instruments (European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire for chronic myeloid leukaemia with 24 items [EORTC QLQ-CML24], EORTC symptom set, Functional Assessment of Cancer Therapy-Leukaemia [FACT-LEU], haematological malignancies patient-reported outcomes [HM-PRO], and MD Anderson Symptom Inventory for chronic myeloid leukaemia [MDASI-CML]) were rated as inconsistent due to not being evaluated by professionals post-development, having very few patients with chronic myeloid leukaemia involved, or missing key symptoms. Moderate-quality to very low-quality evidence underpinned these ratings. The two EORTC instruments were the only ones not to miss key toxic effects (eg, muscle cramps). However, their relevance was rated as inconsistent: the QLQ-CML24 includes questions on health-related quality-of-life, whereas the symptom set includes items sourced from solid cancer treatments. This Review shows the need for an instrument with sufficient content validity to measure toxic effects from TKI treatment in patients with chronic myeloid leukaemia. Until then, stakeholders can make an informed choice from currently used instruments with our assessment.