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Background: Chemotherapy-induced peripheral neurotoxicity (CIPN) is a common complication of cancer treatment that produces functional disability. Increasingly, patient-reported outcome measures (PROMs) are used to assess CIPN, providing a broader symptom perspective than clinician-graded scales. Understanding when a reported change in CIPN symptoms meets the threshold for clinical significance is challenging. This study aimed to provide interpretation guidelines for validated CIPN PROMs, and thereby enable estimation of thresholds to identify clinically relevant symptoms. Methods: Patients commencing neurotoxic cancer treatments were assessed at 3 timepoints: baseline, midtreatment, and end-of-treatment. Trajectory of CIPN development was assessed by means of CIPN PROMs, EORTC Quality of Life – Chemotherapy-Induced Peripheral Neuropathy questionnaire (QLQ-CIPN20), and Functional Assessment of Cancer Therapy/Gynecologic Oncology Group – Neurotoxicity questionnaire (FACT/GOG-NTX). Thresholds were estimated for CIPN PROMs using the NCI CTCAE sensory neuropathy scale as the clinical anchor by midtreatment and end-of-treatment. Patients were assigned to a clinical change group according to CIPN development: either no development; grade 1 neuropathy (minimally important difference [MID]); or grade 2 neuropathy (clinically important difference). Distribution-based estimates (SD, 0.5) were also evaluated as supportive evidence. Results: In total, 406 patients were recruited to the study, of whom 62% (n=199/320) developed CIPN by midtreatment and 80% (n=274/343) by end-of-treatment. Anchor-based MID estimates by midtreatment were 5.06 (95% CI, 4.26–5.86) for the QLQ-CIPN20 and 3.54 (95% CI, 2.87–4.20) for the FACT/GOG-NTX. End-of-treatment MIDs were estimated to be 7.32 (95% CI, 6.23–8.40) for the QLQ-CIPN20 and 4.84 (95% CI, 3.98–5.70) for the FACT/GOG-NTX. Distribution-based MID estimations yielded lower values than anchor-based methods, at 3.73 for the QLQ-CIPN20 and 2.64 for the FACT/GOG-NTX at midtreatment and 5.52 for the QLQ-CIPN20 and 3.64 for the FACT/GOG-NTX at end-of-treatment. Conclusions: Findings from the present series aid meaningful interpretation for commonly used validated CIPN PROMs and provide thresholds that serve as guidance on how to interpret score changes, which will be useful for design and evaluation of clinical trials and clinical practice.

Background: Chemotherapy-induced peripheral neuropathy (CIPN) persists after treatment in up to 40% of cancer survivors and has been linked with increased balance deficits, disabilities, and fall occurrences. This study aimed to comprehensively assess the links between CIPN, balance deficits, and functional disability and to inform the development of clinical screening tools for patients at risk of these events. Patients and Methods: A total of 190 cancer survivors exposed to neurotoxic chemotherapies (age, 57 ± 13 years; average time from completion of neurotoxic therapy, 12 ± 11 months) attended a neurology research clinic for a single cross-sectional assessment of patient-reported and objective CIPN, standing balance in 4 conditions of increasing difficulty, and functional disability. Results: Most patients (68%) reported CIPN symptoms at assessment. Symptomatic patients displayed increased functional disability (F=39.4; P<.001) and balance deficits (F=34.5; P<.001), with degree of balance impairments consistent with a healthy elderly population (age ≥65 years) reporting multiple falls over the subsequent year. Increasing CIPN severity correlated with increasing functional disability (clinically assessed R²=0.46; patient-reported R²=0.49; P<.001) and balance deficits (clinically assessed R²=0.41; patient-reported R²=0.30; P<.001). A 5-factor model of key independent correlates—patient-reported numbness/tingling, weakness, and balance deficit; age; and vibration perception—was strongly linked to balance deficits (R²=0.46; P<.001) and functional disability (R²=0.56; P<.001). Conclusions: This study confirms links between increasing CIPN severity and increasing balance deficits and functional disability using comprehensive CIPN assessment methodology. The extent of balance deficits in patients with CIPN underscores the functional consequences of neurotoxicity. A 5-factor model provides a foundation for clinical screening tools to assess balance deficits and functional disability in patients exposed to neurotoxic chemotherapies.