Letters to Blood To the editor: A pharmacogenetic analysis of the Canadian Cancer Trials Group MY.10 clinical trial of maintenance therapy for multiple myeloma Ming Han, 1 Alli Murugesan, 1 Nizar J. Bahlis, 2 Kevin Song, 3 Darrell White, 4 Christine Chen, 5 Matthew D. Seftel, 5 Kang Howsen-Jan, 6 Donna Reece, 7 Keith Stewart, 8 Yagang Xie, 9 Annette E. Hay, 10 Lois Shepherd, 11 Marina Djurfeldt, 11 Liting Zhu, 11 Ralph M. Meyer, 12 Bingshu E. Chen, 11 and Tony Reiman 1,13 1 Biology, University of New Brunswick, Saint John, NB, Canada; 2 Southern Alberta Cancer Research Institute, University of Calgary, Calgary, AB, Canada; 3 Hematology, Vancouver General Hospital, Vancouver, BC, Canada; 4 Queen Elizabeth II Health Sciences Center, Dalhousie University, Halifax, NS, Canada; 5 Oncology, Princess Margaret Hospital, Toronto, ON, Canada; 6 Oncology, London Health Sciences Centre, London, ON, Canada; 7 Cancer Clinical Research Unit, Princess Margaret Cancer Centre, Toronto, ON, Canada; 8 Centre for Individualized Medicine, Mayo Clinic Arizona, Scottsdale, AZ; 9 Laboratory Medicine, Saint John Regional Hospital, Saint John, NB, Canada; 10 Department of Internal Medicine, Queen’s University, Kingston, ON, Canada; 11 Canadian Cancer Trials Group, Queen’s University, Kingston, ON, Canada; 12 Juravinski Hospital and Cancer Centre and McMaster University, Hamilton ON, Canada; and 13 Department of Oncology, Saint John Regional Hospital, Dalhousie University and University of New Brunswick, Saint John, NB, Canada Multiple myeloma is often treated with high-dose melphalan chemotherapy followed by maintenance therapy with immunomodu- latory agents aimed to delay disease progression and prolong survival. Although it is routinely offered to many patients, randomized trials of maintenance therapy using thalidomide or lenalidomide only dem- onstrated improvement in progression-free survival (PFS), with inconsistent overall survival (OS) benefit. 1-4 Genetic biomarkers predictive of the efficacy and toxicity of immunomodulatory drug maintenance therapy, as well as prognosis following front-line high- dose melphalan therapy, are of potential value in identifying patients best suited for maintenance therapy. Cibeira et al found that single- nucleotide polymorphisms (SNPs) in DNA repair genes were as- sociated with thalidomide response and survival outcome. 5 Johnson et al found several SNP associations with risk of venous thrombosis 6 and thalidomide-related peripheral neuropathy, 7 respectively. Dumontet et al found that SNPs in drug metabolism and DNA repair genes were associated with response to high-dose melphalan and survival. 8 Fern´ andez de Larrea et al found that SNPs in FAM179B and MIR196A were associated with survival after lenalidomide salvage therapy. 9 Well-designed replication studies with independent patient cohorts are crucial in pharmacogenetics to facilitate clinical uptake of predictive biomarkers. In addition, randomized trial design is required for rigorous evaluation of predictive markers associated with benefit or harm from therapy, where the interaction between treatment assignment and outcome can be examined; otherwise, a prognostic marker can be mistakenly identified as predictive. 10 In our study, 44 validation SNPs were selected from previous studies with significant associations with myeloma prognosis and/or thalidomide and melphalan treatment efficacy and toxicity 5-9,11 for validation in the Canadian Cancer Trials Group (formerly named the National Cancer Institute of Canada Clinical Trials Group [NCIC CTG]) MY.10 randomized trial. Fourteen exploratory SNPs in genes shown to be involved in myeloma disease pathways as well as the CRBN-IKZF1/IKZF3-IRF4 pathway, 12-19 which is now known to be central to the mechanism of action of immunomodulatory drugs, were also investigated (the full list of candidate SNPs can be found in supplemental Table 1, see supplemental Data available at the Blood Web site). Exploratory SNPs were chosen due to known functional significance or had clinically significant impact in other disease settings. The MY.10 randomized trial compared thalidomide-prednisone maintenance therapy with observation post high-dose melphalan chemotherapy and autologous stem cell transplant (ASCT). 20 Bone marrow aspirates (n 5 86 treatment arm; n 5 101 observation arm) were obtained (for patient demographic details, see supplemental Table 2). Genomic DNA were extracted and SNP genotypes were assessed by allelic discrimination using TaqMan assays on the ViiA7 platform. To rule out potential discrepancies in SNP genotype be- tween tumor and germ line DNA in our candidate SNPs, concordance assays between tumor and germ line DNA extracted from paired bone marrow and blood samples, respectively, from 9 patients in a separate cohort were conducted and found to be completely concordant for all 58 SNPs. Cox regression models were performed using SAS (version 9.3) for prognostic impact of a single SNP on PFS and OS, with and without adjusted covariates (age, stage, performance status, and re- sponse to ASCT). In treatment benefit analysis, PFS and OS were modeled with genotype, treatment assignment, and their interaction Table 1. SNPs with significant prognostic impact for PFS and OS SNP (rs#) Gene Location Base change Genotype and distribution Association HR 95% CI P rs1672753 CRBN 59UTR A.G GG/GA/AA (4/44/137) PFS 0.59 0.40-0.86 .006 rs1672753 CRBN 59UTR A.G GG/GA/AA (4/44/137) OS 0.55 0.33-0.92 .023 rs2440 XRCC5 39UTR G.A AA/AG/GG (32/79/76) OS 1.70 1.11-2.61 .015 rs4646903 CYP1A1 39UTR A.G GG/GA/AA (1/49/137) OS 1.59 1.04-2.43 .033 rs363717 ABCA1 39UTR T.C CC/CT/TT (7/49/131) PFS 1.44 1.03-2.02 .033 rs361525 TNF-a 59UTR G.A AA/AG/GG (0/18/169) PFS 1.70 1.03-2.81 .037 rs1056836 CYP1B1 Exon G.C CC/CG/GG (42/77/68) PFS 0.72 0.52-0.99 .043 HR represents hazard of patients with at least 1 minor allele vs patients with 2 major alleles. CI, confidence interval. 732 BLOOD, 4 AUGUST 2016 x VOLUME 128, NUMBER 5 For personal use only. on July 23, 2018. by guest www.bloodjournal.org From