Influence of First-Line Regimens on the Outcomes of High-Dose Chemotherapy with Autologous Hematopoietic Stem-Cell Transplantation for Patients with Newly Diagnosed Multiple Myeloma.

Randomized trials that incorporated high-dose chemotherapy (HDC) plus autologous hematopoietic stem-cell transplantation (Au-HSCT) into the early treatment of patients with newly diagnosed multiple myeloma demonstrated superior overall and event-free survival (EFS) in patients 65 years of age or younger, who received Au-HSCT, as compared with patients who received conventional chemotherapy. Based on these encouraging results, Au-HSCT is recommended for patients with myeloma as part of their initial treatment, and today, myeloma is the most common indication for HSCT in the world. All patients in these trials received four to six months of conventional chemotherapy prior to HDC and Au-HSCT. In practice, however, both in the community as well as in academic hospitals, patients are undergoing Au-HSCT after being treated with various first-line regimens, including chemotherapeutics, high-dose dexamethasone (HDex), immunomodulatory drugs such as thalidomide and recently, proteasome inhibitors. In this retrospective study, we examined the impact of first-line therapy on the outcomes following Au-HSCT. Our objective was to compare two treatment groups - chemotherapy versus non-chemotherapy, prior to Au-HSCT - with respect to survival after Au-HSCT. Between 1997 and 2004, 37 previously untreated evaluable patients with myeloma, received either chemotherapy (group 1, n=25; vincristine, adriamycin and dexamethasone (VAD), n=24; melphalan and prednisone (MP), n=1) or non-chemotherapy regimens (group 2, n=12; HDex, n=9; thalidomide plus HDex, n=3), then received HDC followed by cyclophosphamide plus granulocyte colony stimulating factor-mobilized HSCT. The median age of patients in group 1 was 58 (range, 44–73) years and in group 2 was 55 (range, 41–67) years; 22 patients in group 1 (88%) and 10 patients in group 2 (83%) had stage III disease; the median times from diagnosis to HSCT were 6 (range, 5–16) and 8 (range, 5–25) months, respectively, in groups 1 and 2. The rates of complete and near-complete response were 44% in group 1 and 42% in group 2; the rates of partial responses were also similar: 48% and 42% respectively. The median duration of EFS was 31 (range, 7–89) months, and the median overall survival (OS) was 55 (range, 12–98) months in group 1, as compared with group 2 where EFS and OS were 21 (range, 12–40) and 31 (range, 16–76) months, respectively. The EFS at 3 years was 44% in group 1 and 25% in group 2, and OS at 5 years was 32% in group 1 and 8% in group 2 (statistically not significant). In conclusion, patients with newly diagnosed myeloma, when treated with chemotherapy prior to Au-HSCT, may have long-term overall and EFS advantages, as compared with patients who are treated with first-line non-chemotherapy regimens. The reasons for the longer duration of response in the chemotherapy group despite similar response rates in the two groups are unknown, but may be due to more effective suppression of residual disease or non-specific damage to the marrow microenvironment, which is necessary for the growth of myeloma cells. Although, the difference in survival outcomes following Au-HSCT between the two groups did not achieve statistical significance, our results raise an important question regarding the “adequacy” of different first-line regimens prior to Au-HSCT, and therefore, justify the need for prospective randomized studies to evaluate optimal pre-AuHSCT induction therapy.