OBJECTIVES:  In relapsed/refractory multiple myeloma (RRMM), treatments that prolong the treatment-free interval (TFI) are expected to improve patients’ quality of life and to generate economic benefits. Therefore, TFI is an important outcome to consider when assessing the value of new treatments. The aim of this study was to assess the impact of TFI on the clinical and economic outcomes of the association panobinostat, bortezomib and dexamethasone (PAN+BTZ+DEX) vs.BTZ+DEX. METHODS:  A discrete-time Markov-type model was developed to represent RRMM evolution. Adopting the Portuguese healthcare payer perspective, the time horizon defined was two years. BTZ+DEX was set as comparator based on therapeutic guidelines. Efficacy data was extracted from PANORAMA-I trial. Costs were retrieved from public sources. A 5%/year discount rate for costs and effectiveness was adopted. Clinical results were expressed in life time and quality adjusted life time. The economic value was disaggregated in total cost of treatment per month of progression-free survival (PFS) and TFI. RESULTS:  According to model estimates, the treatment with PAN+BTZ+DEX might avoid 5% of progressions and 13% of deaths. The treatment with PAN+BTZ+DEX is associated with an additional 5 months of PFS vs. BTZ+DEX, 4 of which correspond to TFI. Furthermore, TFI is responsible for additional 3 quality adjusted life months (QALM). Despite the increased medication costs of PAN+BTZ+DEX regimen – due to the addition of one more agent – the overall treatment costs are lower. The longer TFI is associated with reduced non-pharmacological costs and with delayed progression to subsequent therapeutic lines. The cost per month of PFS and TFI is lower for PAN+BTZ+DEX vs. BTZ+DEX (4,343€/PFS vs.vs.CONCLUSIONS:  PAN+BTZ+DEX demonstrated to be a more efficient regimen than BTZ+DEX, mainly due to a longer TFI, resulting in additional QALM at a lower cost per month of PFS and TFI.