Background
Updating prognostic models for multiple myeloma is important in the context of changing treatment options. Previously we have described the value of the prognostic marker SKY92, which identifies high-risk multiple myeloma patients, as well as the value of the combined SKY92-ISS marker. With the introduction of revised ISS, it is of interest to evaluate the value of the updated combination of SKY92 with R-ISS. Within the HOVON87/NMSG18 trial, stratification into 3 groups was described: high-risk: 11% SKY92 high-risk (HR) + R-ISS II-III, low-risk: 15% SKY92 standard risk (SR) + R-ISS I and intermediate risk (74%, other). The 3-year PFS rates were 54% (95%CI: 38-77%), 27% (95%CI: 21-37%) and 7% (95%CI: 1-46%) for SKY-RISS I, II and III, respectively (p < 0.001). The 3-yr OS rates for SKY-RISS I to III were 88%, 66% and 26% (p=6×10-7). Here we describe the validation of SKY92-RISS in the CoMMpass dataset.
Methods
SKY92 was determined using RNA-seq data available from the CoMMpass dataset. Briefly, the SKY92 score was obtained as a weighted summation of the expression given by the available Ensembl gene IDs, corresponding to the probe sets of the SKY92 classifier. Renormalization of the original SKY92 discovery data (HOVON65/GMMG-HD4) allowing a direct remodeling between the Affymetrix probe-set expressions (i.e. SKY92) and RNAseq Ensembl gene IDs. Only Ensembl gene IDs with an average log2 expression >8 were used. Revised ISS status was determined as described. For optimal comparison to the discovery cohort of the HOVON87/NMSG18 trial, the analysis was limited to 93 patients older than 65 years in the CoMMpass data set, that did not receive transplant, and for whom RNA-Seq at diagnosis, R-ISS and follow-up data were available.
Results
The median follow-up is 41 months. SKY92 identified 24 high-risk patients (24/93: 26%). The 3-yr PFS and OS rates of standard-risk patients were 49% and 80% respectively, compared to 23% and 44% for high-risk, resulting in a significant log rank test (p < 0.005). The R-ISS classified patients into the low-risk R-ISS I (24% of patients), intermediate-risk R-ISS II (63%) and high-risk R-ISS III (13%). The 3-yr PFS rates were 76% (RISS I), 33% (RISS II) and 33% (RISS III); for OS: 100% (RISS I), 68% (RISS II) and 33% (RISS III; PFS, p = 0.07; OS, p < 0.001). SKY92 and R-ISS were independent prognostic factors in terms of OS and PFS. The SKY-RISS classification resulted in 20% low-, 61% intermediate- and 18% high-risk patients (Figure 1). The 3-yr PFS rates were 81% (95%CI: 64-100%), 42% (95%CI: 30-59%) and 12% (95%CI: 3-44%; p < 0.001) and 3-yr OS rates were 100% (95%CI: 100-100%), 77% (95%CI: 66-89%) and 32% (95%CI: 16-61%; p <0.001).
Out of 69 patients classed as standard risk using the SKY92 classifier (80% 3-yr OS rate), 17 and 52 were classified as SKY-RISS I and II, respectively, resulting in a 3-yr survival rate of 100% and 74%, respectively. In contrast, out of 24 SKY92 HR patients (44% 3 yr OS rate), 5 were classified as SKY-RISS II (100% alive at 3 years) with the remainder true high-risk patients (32% alive at 3 years). Out of 12 RISS III patients (3-yr OS, 33%), 5 were classified as SKY-RISS II (3-yr OS: 60%) and 7 as SKY-RISS III (3-yr OS: 14%).
Conclusion
This study demonstrates the value of gene expression profiling - SKY92 - alongside revised ISS. They form a solid combination, improving on either marker separately. Both models combined clearly identified more high-risk patients correctly, whilst also placing low risk patients into a more appropriate risk category. This was shown in the discovery set and was subsequently applied to an independent set, confirming the validity and usability of the SKY-RISS.
Kuiper:SkylineDx: Current Employment, Current equity holder in private company. Van Vliet:SkylineDx: Current Employment, Current equity holder in private company. Van Beers:SkylineDx: Ended employment in the past 24 months. Zweegman:Celgene: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding. Broijl:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Sonneveld:Sanofi: Consultancy; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Skyline Dx: Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding.
