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Type of economic evaluation
| Cost-utility analysis Partitioned survival model (PSM) |
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Target population
| Adult patients with mycosis fungoides or Sézary syndrome who have previously received ≥ 1 systemic therapy |
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Treatment
| Mogamulizumab (Cycle 1: 1 mg/kg on days 1, 8, 15, and 22; Cycle 2+: 1 mg/kg on days 1 and 15) |
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Submitted price
| Mogamulizumab, 20 mg, IV infusion: $2,203.60 |
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Treatment cost
| Cycle 1: $35,258; cycle 2+: $17,629 |
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Comparator
| ECM; consisting of methotrexate, bexarotene, interferon alpha-2a, gemcitabine, CHOP, liposomal doxorubicin, etoposide, prednisolone, vorinostat, PUVA, extracorporeal phototherapy, total skin electron beam therapy, chlorambucil, purine analogues, pralatrexate, romidepsin, and alemtuzumab) |
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Perspective
| Canadian publicly funded health care payer |
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Outcomes
| QALYs, Lys |
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Time horizon
| Lifetime (30 years) |
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Key data source
| MAVORIC |
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Key limitations
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The comparative impact of mogamulizumab on OS is highly uncertain due to lack of head-to-head evidence for mogamulizumab compared to ECM and the high degree of uncertainty in the sponsor’s MAIC. The sponsor assumed that the effectiveness of ECM would be equivalent to that observed for vorinostat in the MAVORIC trial, which may not be appropriate and adds additional uncertainty to estimates of incremental survival. OS data from MAVORIC are confounded by cross over between treatment arms. The sponsor employed multiple statistical techniques to attempt to address this issue, and the predicted OS varied considerably according to the method chosen. The choice of a PSM to evaluate the cost-effectiveness of mogamulizumab is inappropriate given the high level of uncertainty associated with the OS data from the MAVORIC trial. The sponsor’s model predicts that the majority of gains in LYs and QALYs with mogamulizumab are obtained after disease progression by patients who are receiving subsequent treatment, which lacks face validity. The long-term extrapolation of the clinical effects of mogamulizumab are highly uncertain. Clinical experts consulted by CADTH indicated that the OS predicted by the sponsor’s model for mogamulizumab is likely overestimated. The ECM basket of therapies does not reflect clinical practice in Canada. The composition of the ECM basket and the frequency of use of each included therapy was assumed by the sponsor to be the same regardless of whether patients had mycosis fungoides or Sézary syndrome, which lacks face validity according to clinical experts consulted by CADTH. Incremental costs are therefore unknown. The sponsor employed poor modelling practices in their pharmacoeconomic model, preventing CADTH from fully validating the model and its findings.
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CADTH reanalysis results
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Due to the identified limitations (including structural limitations of the model, immature and confounded OS data, the lack of comparative evidence for mogamulizumab relative to ECM, and an estimate of ECM cost that does not reflect current clinical practice), the cost-effectiveness of mogamulizumab could not be estimated from the sponsor’s submitted evidence, and the cost-effectiveness of mogamulizumab is unknown. Consequently, a price reduction analysis could not be conducted. CADTH undertook an exploratory analysis of the sponsor’s base case to explore the impact of alternative assumptions related to OS. Results of this analysis suggest that the ICER is highly sensitive to uncertainty in the OS data and the method used to reflect the effect of crossover in the MAVORIC trial. Using the sponsor’s base case (which is subject to the limitations detailed above), a 51% price reduction would be required for mogamulizumab to be considered cost-effective at a willingness-to-pay threshold of $50,000 per QALY. This estimate is based on estimates of incremental OS that are likely not representative of the true incremental effect of mogamulizumab. Consequently, the true price reduction that would be needed for mogamulizumab to be cost-effective is unknown but is likely greater than 51%.
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