IMPACT OF USING RELATIVE DOSE INTENSITY VERSUS INDIVIDUAL PATIENT DOSING: A CASE STUDY USING BELANTAMAB MAFODOTIN DATA FROM THE DREAMM-7 STUDY IN RELAPSED/REFRACTORY MULTIPLE MYELOMA
Author(s)
Yevgeniy SAMYSHKIN, MSc1, Molly Purser, MBA, PhD2, Alex Bates, PhD1, Natalie Boytsov, PhD2, Simon McNamara, BSc, MSc, PhD3, Gbenga Kazeem, BSc, MPhil, DPhil3, Ewa Dlotko, MS4, Dawn Lee, MMATH5;
1GSK, London, United Kingdom, 2GSK, Upper Providence, PA, USA, 3GSK, Stevenage, United Kingdom, 4FIECON, London, United Kingdom, 5PenTAG, University of Exeter, Exeter, United Kingdom
1GSK, London, United Kingdom, 2GSK, Upper Providence, PA, USA, 3GSK, Stevenage, United Kingdom, 4FIECON, London, United Kingdom, 5PenTAG, University of Exeter, Exeter, United Kingdom
OBJECTIVES: Cost-effectiveness models (CEM) commonly use a drug’s overall median relative dose intensity (mRDI) to account for deviations from trial protocol dosing; however, overall mRDI may be inappropriate for estimating drug/administration costs for treatments that have dose modifications leading to varying dose intervals over time, such as belantamab mafodotin (belamaf). Data from intent-to-treat population of the phase 3 DREAMM-7 trial of belamaf plus bortezomib/dexamethasone (BVd) versus daratumumab plus bortezomib/dexamethasone (DVd) in relapsed/refractory multiple myeloma were used to evaluate alternative methods for calculating lifetime drug and administration costs in a CEM when dosing intervals are expected to increase over time.
METHODS: United Kingdom drug acquisition and administration costs were estimated and discounted at 3.5%/year. In DREAMM-7, intravenous belamaf dosing intervals were defined as once every 3 weeks, but increased to a median of once every 8 weeks by month 9, with high interpatient variability. For patients remaining on treatment belamaf mRDI declined over time (≤6 months: 77%; >6-12 months: 68%; >12 months: 28%), while daratumumab mRDI remained stable (95-100%). Three costing approaches were assessed: 1) individual patient-level dosing (IPD) data aggregated weekly that accounts for missed doses/actual dose received; 2) overall mRDI; 3) 12-week mRDI (BVd only). mRDI was assessed for patients remaining on treatment.
RESULTS: Compared to IPD, estimated lifetime BVd drug and administration costs were 41% higher using overall mRDI and 21% higher using 12-week mRDI. Lifetime DVd costs using overall mRDI were 9% higher than costs using IPD.
CONCLUSIONS: When doses and dosing intervals vary over time, applying an overall mRDI can inaccurately estimate long-term drug and administration costs compared to IPD weekly data. Accurate methods that reflect observed dosing and treatment patterns are critical for payers and health technology assessment bodies to ensure robust cost-effectiveness evaluations.
FUNDING: GSK (study 300091).
METHODS: United Kingdom drug acquisition and administration costs were estimated and discounted at 3.5%/year. In DREAMM-7, intravenous belamaf dosing intervals were defined as once every 3 weeks, but increased to a median of once every 8 weeks by month 9, with high interpatient variability. For patients remaining on treatment belamaf mRDI declined over time (≤6 months: 77%; >6-12 months: 68%; >12 months: 28%), while daratumumab mRDI remained stable (95-100%). Three costing approaches were assessed: 1) individual patient-level dosing (IPD) data aggregated weekly that accounts for missed doses/actual dose received; 2) overall mRDI; 3) 12-week mRDI (BVd only). mRDI was assessed for patients remaining on treatment.
RESULTS: Compared to IPD, estimated lifetime BVd drug and administration costs were 41% higher using overall mRDI and 21% higher using 12-week mRDI. Lifetime DVd costs using overall mRDI were 9% higher than costs using IPD.
CONCLUSIONS: When doses and dosing intervals vary over time, applying an overall mRDI can inaccurately estimate long-term drug and administration costs compared to IPD weekly data. Accurate methods that reflect observed dosing and treatment patterns are critical for payers and health technology assessment bodies to ensure robust cost-effectiveness evaluations.
FUNDING: GSK (study 300091).
Conference/Value in Health Info
2026-05, ISPOR 2026, Philadelphia, PA, USA
Value in Health, Volume 29, Issue S6
Code
EE154
Topic
Economic Evaluation
Disease
SDC: Oncology