Symptom Burden of Busulfan and Melphalan Versus Melphalan Alone for Multiple Myeloma

Background: High-dose melphalan 200 mg/m² (Mel) is the standard for autologous hematopoietic stem cell transplantation (autoHSCT) for multiple myeloma. Retrospective analyses suggested that a combination of busulfan and melphalan (Bu-Mel) may be associated with a longer progression-free survival (PFS). A secondary aim of a randomized, phase III trial that compared the safety and efficacy of Bu-Mel vs Mel was to compare the symptom burden of the two regimens. Symptom burden is the combined impact of disease- and therapy-related symptoms on patient functional ability.

Methods: Patients were randomized to Bu-Mel (Bu 130 mg/m² daily for 4 days, either as a fixed dose or to target an average daily area under the curve of 5000 μmol-min, followed by 2 daily doses of Mel 70 mg/m)²or Mel (Mel 100 mg/m² daily for 2 days). A subset of patients completed the 20 symptom severity and 6 interference items of MD Anderson Symptom Inventory for Multiple Myeloma (MDASI-MM) prior to the start of the treatment regimen and weekly for 4 weeks post autoHSCT. Symptoms and interference are rated on 0-10 scales (0 = none or no interference, 10 = worst imaginable or complete interference). Differences in individual symptom severity and interference between the two arms were assessed by t-tests and mixed modeling.

Results: As previously reported, 204 (Bu-Mel: 104, Mel: 100) were enrolled between October 2011 and March 2017. At last evaluation, 52 (51%) and 49 (49%) patients achieved a CR (p=0.88), and 69 (68%) and 67 (67%) patients achieved a CR+nCR (p=0.88) in Bu-Mel and Mel arms, respectively. Median PFS was 64.7 months and 34.4 months (p=0.013) in Bu-Mel and Mel arms, respectively. There was no difference in OS between the two arms. One hundred sixty-five of the patients (Bu-Mel: 81, Mel: 84) completed at least one MDASI-MM assessment. Median ages at autoHSCT were 57.2 and 57.0 years in Bu-Mel and Mel groups, respectively (p=0.86). At baseline, t-tests showed significantly higher mean severity of constipation (1.80, standard deviation [SD] = 2.87 vs 0.98, SD = 1.94; p=0.036), muscle weakness (2.38, SD=2.49 vs 1.44, SD=1.87; p=0.034), diarrhea (1.45, SD=2.43 vs 0.60, SD=1.10; p=0.005), and global symptom interference (2.96, SD=2.81 vs 1.77, SD=2.00; p=0.003) in the Bu-Mel arm than the Mel arm. The Bu-Mel patients had a significantly higher mean severity of pain (5.67, SD=2.65 vs 3.17, SD=3.07; p=0.0043) and mouth sores (7.35, SD=2.41 vs 1.25, SD=2.22; p <0.0001) than the Mel patients 7 days post autoHSCT. Longitudinal analysis using mixed modeling showed that the Bu-Mel arm had a significantly higher mean severity of pain (ED = 1.102, p=0.003), drowsiness (ED = 0.674, p=0.040), dry mouth (ED = 0.904, p=0.009), constipation (ED = 0.695, p=0.006), muscle weakness (ED = 0.815, p=0.006), mouth sores (ED = 1.683, p <0.0001), rash (ED = 0.362, p=0.019), and interference with physical functions (general activity: ED = 1.015, p=0.010; working: ED=1.229, p=0.006; walking: ED=0.920, p=0.009) than the Mel arm during the 4 weeks following autoHSCT.

Conclusions: Patients receiving Bu-Mel vs Mel prior to autoHSCT report some differences in symptom severity, with Bu-Mel patients experiencing more severe sore mouth, pain, and symptom interference with daily functioning. The greater intensity of the double-alkylating agent conditioning regimen of Bu-Mel likely led to these differences. The increased severity of drowsiness, dry mouth, constipation, and muscle weakness may be due to an increased need for opioids to control severe pain and mouth sores. The effect of significant differences in symptom severity and interference at baseline between these two groups, despite randomization, is not clear. However, the longer time to progression of myeloma with the Bu-Mel regimen may offset the greater symptom burden early post autoHSCT. Systematic measurement of symptom burden during clinical trials can provide useful information for clinicians and patients in evaluating the full impact of different treatment regimens and enhance treatment decision making and discussion between clinicians and patients.