Impact of Etiological Cytogenetic Abnormalities on Immunoparesis and Progression-Free and Overall Survival in Newly Diagnosed Multiple Myeloma

Introduction: Immunoparesis, or suppression of polyclonal immunoglobulins, is a common issue in multiple myeloma (MM). Prior studies have shown that the degree of IgM immunoparesis is prognostic for survival, as patients with the most severe IgM immunoparesis at diagnosis have the poorest survival outcomes. Little is known regarding the cause of this immunoparesis, with many assuming it is due to tumor bulk alone. More recent data has suggested that MM can be divided into subgroups with distinct biologies and outcomes based on etiological cytogenetic abnormalities. These include hyperdiploidy and translocation t(11;14), t(4;14), t(14;16), or t(14;20), with the latter three groups being associated with high-risk disease. We hypothesized that the different etiological cytogenetic abnormalities drive bone marrow microenvironmental changes, resulting in different degrees of immunoparesis and subgroup-dependent effects on clinical outcomes.

Methods: We performed a retrospective review of newly diagnosed MM patients enrolled in the MRC Myeloma IX and Cancer Research UK Myeloma XI trials. Patients with hyperdiploidy, t(11;14), t(4;14), t(14;16), or t(14;20) were included in the analysis. Polyclonal IgG, IgA, and IgM levels were measured at diagnosis, and the normal range was established by the 5th - 95th percentiles of adults over age 45 years in the UK: IgG 6 - 16 g/L, IgA 0.8 - 4 g/L, and IgM 0.5 - 2 g/L. Cytogenetic abnormalities were determined by FISH, multiplex ligation-dependent probe amplification (MLPA), or next generation sequencing (NGS). Overall survival (OS) was defined as time from date of trial entry to date of death, or censored at date last known to be alive. Progression-free survival (PFS) was defined as time from date of trial entry to progression or death, or censored at date last known to be alive and progression-free.

Results: The study included 985 patients, of whom 47% were at least age 65 years and 61.1% were male. The most common MM subtype was IgG (63.4%), followed by IgA (24.5%), light chain only (8.4%), IgD (1.9%), oligosecretory (1.0%), IgM (0.5%), and non-secretory (0.3%). Hyperdiploidy represented 58.9% of cases, with t(11;14) seen in 18.2%, and t(4;14), t(14;16), or t(14;20) seen in 22.9%. The MM subtype was not distributed evenly amongst the different etiological cytogenetic abnormalities with IgG overrepresented in the hyperdiploid subgroup (69.4%), compared to 11% in t(11;14) and 19.5% in high-risk cases. IgA was overrepresented in high-risk cases (45.2%), compared to 41.1% in hyperdiploidy and 13.7% in t(11;14).

The high-risk subgroup had more immunoparesis compared to the hyperdiploid and t(11;14) subgroups (median polyclonal IgG 3.0 vs. 3.8 vs. 3.9 g/L, IgA 0.2 vs. 0.4 vs. 0.2 g/L, IgM 0.1 vs. 0.2 vs. 0.2 g/L, respectively). There were also significantly more patients in the high-risk subgroup with polyclonal immunoglobulin levels below the normal range compared to the hyperdiploid and t(11;14) subgroups (IgG 96.9% vs. 86.0% vs. 88.2%, p = 0.0045; IgA 89.9% vs. 77.1% vs. 92.4%, p < 0.0001; IgM 94.0% vs. 88.9% vs. 92.7%, p < 0.0001).

With median follow up of 77 months, the overall median PFS and OS were 19 months and 53 months, respectively. As expected, patients in the high-risk subgroup had significantly lower PFS and OS (14 and 35 months, respectively, p < 0.001), compared to the hyperdiploid (21 and 60 months) and t(11;14) subgroups (22 and 53 months). The effect of the degree of immunoparesis on PFS depended on the cytogenetic subgroup. Using polyclonal IgM as a continuous variable, Cox regression analysis demonstrated a significant effect on PFS in patients with hyperdiploidy (HR 0.482, 95% CI 0.325 - 0.717, p = 0.0003). No difference was seen in the t(11;14) (HR 0.610, 95% CI 0.262 - 1.418, p = 0.2507) or high-risk subgroups (HR 1.087, 95% CI 0.505 - 2.341, p = 0.8304).

Conclusions: Our study demonstrates that the etiological cytogenetic subgroup influences the degree and clinical impact of immunoparesis in newly diagnosed MM patients. A significant proportion of patients with t(4;14), t(14;16), or t(14;20) have IgG, IgA, and IgM levels below the normal range compared to patients with hyperdiploidy and t(11;14). This suggests that the underlying genetic abnormality (i.e., NSD2, C-MAF, and MAF-B, respectively) drives changes in the bone marrow microenvironment remodeling the plasma cell niche, resulting in suppression of normal plasma cell function and immunoglobulin levels.