Predictors of Overall Survival for Multiple Myeloma Patients Depending on Transplant Status According to a Retrospective, Non-Interventional Study in Norway

Introduction

Multiple myeloma (MM) is the second most common hematological malignancy in Europe and the US. The median survival after diagnosis is approximately 4-5 years (Röllig et al The Lancet 2015), with recent improvement observed in younger (Kyle et al Expert Rev Hematol 2014) and older patients (Kumar et al Leukemia 2013). The improvement in outcomes of MM patients is largely due to the introduction of autologous stem cell transplant (ASCT) and novel treatments including proteasome inhibitors and immunomodulators. Norwegian guidelines state that the preferred frontline treatment for MM patients under 65-70 years old is ASCT, but this option may be limited by comorbidity. Here, we report results from a retrospective, non-interventional study using data collected at the MM registry at Oslo University Hospital (OUS), Norway. The aim was to describe patient and disease characteristics, overall survival (OS), and potential predictors of death for the study population in Norway.

Methods

The study period was from 1 Jan 2008 to 31 Dec 2015. Patients (n=169) aged 18 years or older at MM diagnosis and who were treated at OUS (ASCT or not) or in 1 of 5 regional hospitals (ASCT only, with ASCT received at OUS and other treatments received locally), during the study period, were included. Study entry was defined as date of MM diagnosis and follow-up started from study entry. End of follow-up occurred at the first of: end of study period, loss to follow-up, or death. Variables used were part of routine practice. Descriptive analysis was done at diagnosis for the overall population, for patients who received ASCT (n=100), and for those who did not receive ASCT at any time during the study period (n=69). At treatment line 1, Cox models were used to identify potential predictors for OS.

Results

In the study, 55.6% of patients were diagnosed with MM at OUS and 25 of those patients (14.8% of total population) received ASCT. Patients who did not receive ASCT were older and included a larger percentage of women than in the transplant cohort (mean age non-ASCT 73.1±11.2 with 55.1% women and for ASCT 55.5±6.7 years with 45.0% women).

More MM patients were diagnosed with Bence Jones (BJ) (21.9% of patients) or IgG type myeloma (54.4% of patients) than IgA type (20.1% of patients) (Table 1). Of transplant patients, more were of International Staging System (ISS) stage I or stage II than stage III MM, though 35.0% of patients were of unknown stage. Most non-transplant patients had unknown ISS stage, followed by stages II and III and the least number of patients were of stage I.

Of the CRAB symptoms at diagnosis, most ASCT patients showed no hypercalcemia (80.0%), no renal impairment (90.0%), or no anemia (68.0%), and 34.0% presented with skeletal destruction (Table 1). Similarly, most non-transplant patients had no hypercalcemia (87.0%) and no renal impairment (79.7%) at diagnosis. Anemia and skeletal destruction were not measured in 24.6% of non-transplant patients. Of those with recorded results, more non-transplant patients had skeletal destruction than not and approximately the same number of non-transplant patients presented with anemia than not. High-risk cytogenic abnormalities, a criterion of the revised (R)-ISS, was unknown for most patients (80.5%).

Median OS from start of treatment line 1 was 75.93 (90% confidence interval (CI): 68.23 to not reached) months for transplant patients and 34.20 (90% CI: 25.57-42.16) months for non-transplant patients. Variables including age group, sex, CRAB symptoms at diagnosis, type of first therapy, and type of MM at diagnosis were included in the Cox models per cohort, if they had a missingness of <20%. Hypercalcemia at diagnosis was a significant predictor for OS for the transplant cohort, while anemia at diagnosis gave a decreased risk of death. Hypercalcemia as well belonging to the older age groups (e.g., 61-70 years and 71-80 years) were significant predictors of death for the non-transplant patients (Table 2).

Conclusions

For MM patients in Norway, overall survival was much greater for patients receiving transplant in the first line. Hypercalcemia at diagnosis predicted death for both transplant and non-transplant cohorts and anemia at diagnosis was identified as a decreased risk of death for transplant patients, but not well-recorded for non-transplant patients. Belonging to an older age group (>71 or 80 years old) also was a significant predictor of death, but only for non-transplant patients.