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The combination of panobinostat, bortezomib and dexamethasone (PanBorDex) is available as a treatment option for relapsed refractory multiple myeloma (RRMM) based on the PANORAMA-1 trial which investigated this triplet in early relapse. In routine clinical care, PanBorDex is used primarily in later relapses and is commonly administered in attenuated dosing schedules to mitigate the treatment-related toxicity. We set out to evaluate efficacy and safety outcomes with PanBorDex later in the disease course and evaluate the role of attenuated dosing schedules. This was a retrospective evaluation of patients treated in routine clinical practice between 2016-2019 across seven heamatology centres in the UK; patients who received at least one dose of PanBorDex were eligible for inclusion. The dosing schedule of panobinostat (10mg, 15mg or 20mg, twice or three times a week) and bortezomib (0.7mg/m2, 1mg/m2 or 1.3mg/m2 once or twice weekly) was as per treating physician choice. Patients received treatment until disease progression or unacceptable toxicity. The primary outcome is response rates according to IMWG criteria. Key secondary endpoints include progression-free survival (PFS) and overall survival (OS). Other secondary endpoints include rates of adverse events according to CTCAE criteria. In total, 61 patients were eligible for inclusion and received PanBorDex primarily as ≥5th line of treatment. One third of patients received PanBorDex at full dose, for the remaining two thirds, treatment was given in reduced dose intensities. The overall response rate was 44.2%, including 14.7% very good partial response (VGPR) rates; 68.8% of patients derived clinical benefit with stable disease or better. The median PFS was 3.4 months; non-refractory patients and those who achieved VGPR benefited from prolonged PFS of 11.4 months and 17.7 months, respectively. The median OS was 9.5 months. The triplet was associated with 45% and 18% incidence of grade 3-4 thrombocytopenia and diarrhea, respectively., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: N. Maouche: Takeda UK; honorarium, consultancy fees, speaker fees, conference attendance, grant, Celgene; speaker fees, Novartis; speaker fees, Janssen; conference fees, Abbvie; conference fees. B. Kishore: Celgene; consultancy, Takeda UK; conference attendance, BMS; conference attendance, Janssen; conference attendance, Shire; advisory board. Z. Bhatti: None Declared. B. Supratik: None Declared. F. Karim: None Declared. S. Sundararaman: None Declared. F. Collings: Celgene; Speaker fees, Takeda; Speaker fees. B. Tseu: None Declared. H. Leary: None Declared. N. Ryman: None Declared. U. Reddy: None Declared. G. Vallance: Jazz Pharmaceuticals; grant, Takeda UK; grant. J. Kothari: None Declared. K. Ramasamy: Janssen; grant, speaker fees, advisory board, Novartis; advisory board. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Bortezomib, a first generation proteasome inhibitor, is used in both newly diagnosed and relapsed myeloma settings. Considerable differences exist in the usage of bortezomib therapy in the clinical practice setting in comparison to clinical trial setting as well manufacturer's recommendations. These differences include route of administration (intravenous (iv) vs. subcutaneous (sc)), frequency from twice to once weekly, choice of alkylating agent used in combination with bortezomib (melphalan or cyclophosphamide), and choice of glucocorticoids (dexamethasone or prednisolone). We reviewed data from 272 consecutive bortezomib-treated myeloma patients, who received therapy within the regional Thames Valley Cancer Network for both newly diagnosed myeloma (NDMM, n = 120) and relapsed MM (RMM, n = 152). We investigated the influence of age, sex, transplant, bortezomib combinations (doublet vs. triplet), cumulative bortezomib dose per treatment line (<50mg vs. ≥50mg), and route of administration (iv vs. sc) on time to next treatment (TTNT) and on overall survival (OS). Route of bortezomib administration (iv vs. sc) influenced neither OS (41 vs 35 months, p = 0.5), nor TTNT (14 vs. 19 months, p = 0.052). Our study showed a statistically significant improvement in median OS in patients receiving a cumulative dose ≥50mg compared to <50mg (42 vs. 33months, p = 0.003), although presence of confounders need to be taken into account, such as disease stage, performance status, genetic changes and prior therapies. Median OS was longer using triplet therapies compared to a doublet in the RMM cohort (37 vs. 29 months, p = 0.06), although this did not reach statistical significance. Multivariate Cox Regression analysis showed that cumulative bortezomib dose ≥50mg (p = 0.002, HR = 1.83, 95% CI 1.25-2.67) and autologous transplant (p = 0.002, HR = 2.6, 95% CI 1.41-3.98) were both significant factors associated with improved OS. Our data argues in favour of continuing bortezomib for the recommended duration as per Summary of Product Characteristics (SPC), subject to good tolerability, in order to deepen response or extend the duration of best response., Competing Interests: The authors have declared that no competing interests exist.

Double relapsed and/or refractory multiple myeloma (DRMM), MM that is relapsed and/or refractory to bortezomib and lenalidomide, carries a poor prognosis. The healthcare costs of DRMM have not previously been reported. We analyzed detailed medical resource utilization (MRU) costs, drug costs and outcomes for 39 UK patients receiving standard DRMM therapy. Median OS in this cohort was 5.6 months. The mean cost of DRMM treatment plus MRU until death was £23,472 [range: £1,411-£90,262], split between drug costs £11,191 and other resource use costs £12,281. The cost per assumed quality-adjusted life year (QALY) during DRMM was £66,983. These data provide a standard of care comparison when evaluating the cost-effectiveness of new drugs in DRMM.