Peripheral Neuropathy in the Cassiopeia Study

Introduction
Peripheral neuropathy (PNP) remains one of the most common adverse events during multiple myeloma (MM) treatment. The immunomodulatory agent thalidomide and proteasome inhibitor bortezomib are particularly prone to induce PNP (Dimopoulos MA et al., Leukemia., 2010). Both agents are part of standard treatment regimens for newly diagnosed transplant-eligible MM patients. PNP varies from mild symptoms to severe disability, depending on timely dose reduction or discontinuation of treatment. Currently, incidence or severity of PNP cannot be predicted. Therefore, it is of utmost importance to monitor incidence of PNP in different treatment combinations, and in order to identify risk factors for developing PNP.

Aims
To investigate the incidence of PNP in patients treated in the Cassiopeia trial, to evaluate the role of CD38 antibody (daratumumab) treatment in development of PNP, and to identify risk factors for the development of PNP.

Methods
We retrospectively analysed incidence of PNP grade 2 to 4, scored according to common terminology criteria for adverse events version 4 (CTCAE) in the Cassiopeia study, a phase III trial conducted by IFM/HOVON, investigating the efficacy of adding daratumumab to bortezomib, thalidomide and dexamethasone (VTD). 1074 newly diagnosed MM patients were randomised. Patients received 4 induction cycles and 2 post transplantation consolidation cycles of 28 days each. Cycles included subcutaneous bortezomib (1.3 mg/m² days 1,4,8,11), oral thalidomide (100 mg daily), dexamethasone (20-40 mg) and daratumumab intravenously (16 mg/kg and weekly during induction cycles 1 and 2 and once every two weeks during induction cycles 3,4 and consolidation). This trial was registered as ClinicalTrials.gov NCT02541383 and was supported by the French IFM and Dutch HOVON groups (Moreau et al., Lancet, 2019).
Multivariate analysis was performed including sex, age, arm, body mass index (BMI), cytogenetics, ISS stage, country, diabetes mellitus (DM), creatinine clearance, liver function, ECOG, baseline PNP and disease characteristics.

Results
Baseline characteristics in dara-VTD and VTD arms were similar. Overall, 380/1074 (35%) patients developed grade ≥2 PNP and 102/1074 (9%) patients developed grade ≥3 PNP. Multivariate analysis indicated that the cumulative incidence of PNP grade ≥2 was significantly lower in the dara-VTD arm (33%) when compared to the VTD arm (38%) (hazard ratio (HR)=0.73, 95% confidence interval (CI) 0.59-0.91, P=0.004). Furthermore, risk factors associated with a higher cumulative incidence of PNP grade ≥2 included older age (HR=1.03; P=0.020), grade 1 PNP at baseline (HR= 2.75; P= 0.002) and higher BMI (HR=1.46, P=0.003 for BMI 25-30 to HR=2.02, P=0.004 for BMI > 35). Progression free survival (PFS) from the end of induction was similar (86% vs 80% at 2 years, HR = 0.74, 95% CI 0.41-1.33, P=0.32) for patients developing grade ≥2 PNP during induction (179 pts, 17%). An unexpected finding was the difference in cumulative incidence between countries participating in this trial: in the Netherlands 68/141 (49%) of patients developed grade ≥2 PNP, while in France this was 280/846 (33%) and in Belgium 31/87 (36%) (p<0.001).
The protocol of the Cassiopeia trial included instructions of discontinuation and dose modification, when PNP grade ≥2 was observed. However, in a subset of patients reaching PNP grade ≥ 2 the (temporary) discontinuation or adjustment of dose as described in the treatment protocol had not been applied (respectively in 148/352 (42%) with PNP ≥ 2 and in 39/97 (40%) with PNP ≥3).

Conclusions
Despite bortezomib being administered subcutaneously and clear instructions on discontinuation and dose modification, we observed a clinically relevant incidence of grade ≥2 PNP (35%) and grade ≥3 PNP (9%) in patients treated in the Cassiopeia trial. Patients in the dara-VTD arm showed less grade ≥2 PNP, suggesting a possible positive effect of daratumumab. Risk factors for the development of grade ≥2 PNP included older age, PNP at baseline and BMI > 25. Differences in incidence between countries were observed, however no clear explanation was found. Furthermore, standard measures for grading PNP, such as CTCAE criteria, are subject to interpretation bias of both the patient and the treating physician. Continuous screening and correct grading of PNP and strict compliance with guidelines is warranted.