Estimating time toxicity of maintenance rituximab in indolent lymphomas.

361 Background: Time toxicity (TT) refers to the total time a patient (pt) spends receiving cancer care. This measure is particularly relevant when treatment is unlikely to improve overall survival (OS). Maintenance rituximab (MR) for indolent lymphomas following chemotherapy induction is often considered standard of care, but its value is debated. MR may prolong progression-free survival (PFS) and reduce transformation risk, but its impact on OS is uncertain, and it may increase toxicity and cost (Zhang, 2017). TT can further inform decisions about MR use, but estimates are lacking. Methods: We applied the TT framework by Gupta et al. (2022), which quantifies planned and unplanned TT in days, to pts receiving MR. We reviewed phase III trials (PRIMA 2011, GALLIUM 2018, MabCute 2021) that included MR arms and reported adverse events (AEs). Planned TT was based on MR protocols (12 infusions over 2 years). Unplanned TT was estimated using reported rates of AEs, with care time informed by prior TT studies in other cancers. Results: Planned TT was estimated at 18–24 days over 2 years. No trials reported average number of AEs experienced during maintenance per pt (i.e., frequency of repeat events or multiple events); for modeling purposes a range of 1-2 events was assumed. Unplanned TT from AEs contributed an additional 2–6 days. In 6–20% of pts IVIG infusions for hypogammaglobulinemia are required, and would add up to 24 more days of unplanned TT. On average, pts receiving MR can expect 20–30 days of TT, with a maximum of 54 days for those needing IVIG. Conclusions: We estimate MR for indolent lymphoma is associated with a mean of 25 days of TT, with a range of 20-54 days. Significant data gaps exist and validation is needed, either through prospective TT analyses in future MR trials or claims review. Pending validation, TT estimates may support shared decision-making in lymphoma care for pts considering MR. TT Bucket Encounter Type # Cycles / Events Days per Event % of Patients Est. TT in Days Planned Lab Visit 6-12 1 100% 6 - 12 Infusion + Clinic Visit 12 1 100% 12 Subtotal 18 - 24 Unplanned Grade 1-2 AEs 1-2 2 33-46% 0.7 - 1.9 Grade 3-4 AEs 1-2 6 24-34% 1.4 - 4.0 IVIG 12-24 1 6-20% (0 - 24) Subtotal 2 - 6 (+0 - 24) TOTAL 20 - 30 (+0 - 24)