Immunotherapy access disruptions in Mexico: Real-world delivery irregularities at a public cancer referral center.

1511 Background: Immunotherapy improves outcomes in selected cancers, but access in middle-income countries may be limited by cost and supply instability. We quantified eligibility, initiation, and delivery disruptions attributable to drug unavailability at a public cancer referral center in Mexico. Methods: Retrospective cohort of adults with a first oncology consultation at Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (Mexico City) between January 2023 and March 2025. Records were reviewed to identify standard indications for immunotherapy per NCCN/ESMO/ASCO guidelines current at evaluation. Among eligible patients, we assessed initiation and delivery fidelity. Deviations were defined as delay to initiation >30 days, regimen modification, or temporary/permanent suspension due to drug shortages. Results: Among 1,201 first-time consultations, 228 (18.9%) had an immunotherapy indication; 114/228 (50.0%) initiated immunotherapy. Among eligible patients who did not initiate (n=114), medication unavailability was the most frequent reason (48, 42.1%). Among treated patients (n=114), delivery disruptions were common: 42 (36.8%) had treatment suspensions due to shortages, 9 (7.9%) received regimens deviating from approved protocols, and 8 (7.0%) started with >30-day delay. Overall, only 55/228 (24.1%) immunotherapy-eligible patients received treatment as recommended by international guidelines. Conclusions: In this public Mexican referral center, only half of immunotherapy-eligible patients initiated treatment, and over half of treated patients experienced delivery disruptions linked to drug unavailability. These findings support urgent procurement and supply-chain strategies to ensure timely, uninterrupted access to high-impact cancer therapies in publicly funded systems. Extent of immunotherapy eligibility, initiation, and delivery disruptions attributable to drug unavailability. Measure Value First-time oncology consultations 1201 Immunotherapy indication 228 (18.9%) Initiated immunotherapy 114/228 (50.0%) Non-initiation due to medication unavailability 48/114 (42.1%) Any delivery irregularity among treated patients 59/114 (51.8%) Suspension due to drug shortages 42/114 (36.8%) Regimen deviation due to unavailability 9/114 (7.9%) Initiation delay >30 days 8/114 (7.0%) Guideline-concordant immunotherapy among eligible patients 55/228 (24.1%) Values are n (%) unless otherwise indicated. Delivery irregularities include initiation delay >30 days, regimen modification, or temporary/permanent treatment suspension due to drug shortages. Percentages are calculated using the denominators specified in each row.