P-144: Oral Symptom Assessment using Patient Reported Outcomes (PRO) for Relapsed Multiple Myeloma Patients treated with Talquetamab

Introduction: Talquetamab (Tal), a GPRC5D bispecific antibody has significant clinical efficacy in relapsed refractory multiple myeloma (RRMM). However patients commonly report oral symptoms which may impact quality of life. These are not well characterised using standard CTCAE criteria or myeloma specific questionnaires. We therefore used validated oral health-specific questionnaires to better define symptoms.

Methods: Triple class exposed RRMM patients received Tal 0.8mg/kg Q2W after a step-up phase. Oral health-specific questionnaires: NCI Patient Reported Outcomes version of the Common Terminology Criteria for Adverse Event (NCI-PRO-CTCAE) (Q1-9), Xerostomia inventory and Scale of Subjective Total Taste Acuity (STTA) and EORTC-QLQ-C30 were performed at baseline, weekly for the step-up phase, every cycle through 1-5, every 3 cycles until end of treatment and at 1, 3, and 6 months post end of treatment. Supportive treatments included: saliva substitutes, dexamethasone mouthwash & nutritional supplements.

Results: 11 patients (4 female, 7 male; median 60 y (range 51-71)), with a median of 5 prior lines (range 4-10) completed 107 questionnaires over a median follow-up of 9.1 months. Compliance for questionnaires was 91%. 9 of 11 (82%) patients responded (≥PR) and 3 are ongoing.

At baseline, 7 patients reported dry mouth (median: occasional frequency/mild severity) and 3 reported up to moderate taste changes.

At week 2, there were significant increases (p=< 0.05) in dry mouth frequency (median: frequent) & severity (median: moderate). Taste significantly worsened (p=< 0.05) by: severity (median:moderate), impact on daily life (median:sometimes). The STTA score deteriorated to 2 (moderate taste loss, sometimes inconvenient) and significant reductions (p< 0.05) occurred in appetite (median:moderate). The EORTC QLQ-C30 global health status score reduced by a median of 16.7 (p=0.031) and role functioning reduced by 33.3 (change by 10 = significant). All other scores remained stable.

At week 3 there were further significant increases in difficulty swallowing (median:moderate, p=0.047), worsening of taste impact to frequent (range:not at all to always), difficulty eating dry foods (median:frequently). The median STTA score worsened to severe taste loss, frequently inconvenient. Additionally, there were further reductions in global health status (median 20.8) and role functioning (median 33.3). PROs detected taste changes earlier than clinician assessment (PRO:day 7, clinician:day 10)

However by cycle 3, an improvement in global health status was observed and maintained. Oral symptoms persisted with individual variations. Patients stopping treatment showed improvements in taste, appetite loss and dry mouth at 3 months after last dose.

Conclusions: Oral specific PROs demonstrated a significant worsening of oral symptoms, global health status with Tal by week 2 followed by an improvement in global health status. Oral symptoms improved by 3 months in those stopping.