The contribution of baseline values of involved HLC (iHLC) and uninvolved HLC (uHLC) to the risk of progression was also studied [36]. When IgG and IgA patients were grouped together and categorised by tertiles of iHLC or uHLC concentrations, patients who had iHLC concentrations in the top tertile had significantly shorter PFS (HR 1.4, p=0.039; Figure 20.10A). However, suppressed concentrations of uHLC concentrations were even more significantly associated with shorter PFS (HR 1.8, p=0.002; Figure 20.10B). No significant association was observed between PFS and concentrations of the non-tumour immunoglobulin isotypes (i.e. classical immunoparesis).

The current international staging system (ISS) for MM relies upon serum β_{2}M and albumin measurements (Section 20.1) [429]. The correlation between these measurements and PFS is shown in Figure 20.10C (p=0.017) [36]. In univariate analysis, extreme HLC ratios had a greater prognostic significance (p=0.017) than albumin (p=0.153) on PFS. Concordant with this, in multivariate analysis, elevated β_{2}M (>3.5 mg/L) and extreme HLC ratios (<0.01 or >200) were the only independent variables to identify patients with reduced PFS, whereas other variables (albumin <35 g/L; κ/λ sFLC ratios, and cytogenetic abnormalities [Del:13, t4:14, Del:17p]) did not reach significance. A risk-stratification model was developed in which patients were grouped into three categories: low risk (β_{2}M <3.5 mg/L and HLC ratio 0.01 - 200), intermediate risk (either β_{2}M >3.5 mg/L or HLC ratio <0.01 or >200), or high risk (both β_{2}M >3.5 mg/L and HLC ratio <0.01 or >200) (Figure 20.10D). In this model, the high risk group was more significantly associated with shorter PFS than ISS stage III disease (p=0.000002).

The prognostic value of HLC-pair suppression was also studied by Ludwig et al. [903] in a study of 156 newly diagnosed MM patients. Three categories of HLC-pair suppression were defined: no suppression; moderate suppression (below the lower normal limit and up to 50% suppression), and severe suppression (a >50% reduction below the lower normal limit). Patients with severe HLC-pair suppression had significantly shorter OS compared with patients in both other groups combined (median 45.4 vs. 71.9 months, HR: 1.616, p=0.019). On multivariate analysis, severe HLC-pair suppression remained independently associated with survival when all patients were considered (HR: 2.553, p=0.013), and when IgG patients were studied separately (median 46.4 vs. 105.1 months, HR: 1.839, p=0.017).