Peripheral Neuropathy Symptoms, Pain and Functioning in Relapsed or Refractory Multiple Myeloma Patients Treated with Selinexor, Bortezomib, and Dexamethasone

Introduction: The BOSTON study is a Phase 3 trial comparing the novel triplet regimen of once weekly oral selinexor with once weekly bortezomib and dexamethasone (SVd) versus standard twice weekly Vd in patients with multiple myeloma (MM) after 1-3 prior therapies. The SVd regimen conferred a 47% increase in median progression-free survival (PFS) and time to next therapy (TTNT), higher overall response rates (ORR) and deeper responses compared to Vd. Furthermore, this is the first trial of a bortezomib-based triplet therapy (i.e., SVd) that showed lower rates of overall and Grade ≥2 peripheral neuropathy (PN) compared with doublet Vd while conferring a longer PFS, and the regimen requires ~35% fewer clinic visits than standard twice weekly Vd. This abstract reports analyses of the patient reported outcomes (PROs) in BOSTON to evaluate patterns in therapy-induced PN symptoms, pain and function.

Methods: PROs were assessed at baseline and day 1 of each cycle using the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 and EORTC QLQ‑CIPN20 questionnaires. The QLQ-CIPN20 assesses patients’ experience of symptoms and functional limitations related to chemotherapy induced PN (CIPN) and has 3 subscales: sensory, motor, and autonomic. The QLQ-C30 includes several functional and symptom scales and focuses on physical functioning, role functioning, and pain subscales as pre-specified domains of interest. Mixed effects repeated measures models were fit to the longitudinal data to estimate differences over time. Meaningful change thresholds derived using anchor- and distribution-based methods or estimated from the literature were used to identify patients who had experienced a meaningful worsening of symptoms or deterioration in functioning. Time to definitive deterioration was defined as the time from randomization to the first occurrence of meaningful deterioration that was not followed by subsequent improvement. Cox proportional hazard models compared the hazard rates between arms adjusted for baseline questionnaire score, randomization stratification factors (prior PI therapy, number of prior anti-MM regimens, R-ISS stage at MM) and prior bortezomib exposure.

Results: A total of 402 patients were enrolled in the trial; 388 completed a baseline QLQ-CIPN20 assessment and are included in these analyses. Based on the mixed model repeated measures analysis (Table 1), a benefit was demonstrated for SVd in change from baseline to Day 106 for sensory (-5.3 points difference, p=0.0006) and pain (-6.6, p=0.007) scores. Patients in the SVd arm had a greater increase in autonomic symptom scores (+5.0, p=0.022).

The number of patients with definitive deterioration in QLQ-CIPN20 sensory symptoms was greater in the Vd arm (86 patients, 45.7%) compared to 52 (27.7%) patients in the SVd arm (Table 2). The median time to deterioration was 20.7 months (95% confidence interval [CI]: 15.4, not estimable [NE]) in the SVd arm compared to 12.5 months (95% CI: 7.8, 19.9) in the Vd arm. The adjusted hazard ratio (HR) comparing time to deterioration in sensory scores between SVd and Vd arms was 0.53 (95% CI: 0.38, 0.75; p = 0.0004). Worsening of motor symptoms also trended in favor of SVd with a HR = 0.72 (p=0.052). Roughly half of the patients in each treatment arm experienced worsening autonomic symptoms (54.6% and 48.4%, SVd and Vd respectively) with no significant difference between arms (HR=1.14, p=0.37). While not statistically significant, fewer SVd patients had definitive deteriorations in pain and physical function compared to Vd patients, with similar or extended time to deterioration (Table 2).

Conclusions: In the setting of a significant increase in PFS and TTNT, patients with MM after at least one prior therapy who received weekly SVd reported lower sensory symptom and pain scores but higher autonomic symptom scores. Further, patients treated with twice weekly Vd experienced a more rapid rate of sensory symptom worsening and a trend to more rapid worsening of motor symptoms, compared to patients treated with SVd. The improved pain scores in patients treated with SVd may be related to superior disease control. The reduction in PN-related pain and sensory symptoms observed with SVd in the setting of increased PFS and TTNT supports a potentially improved patient experience and decreased health care burden and long term morbidity.