Correlation of Erythropoietin Stimulating Agents (ESAs) with the Post-Therapy Micro-Vessel Density (MVD) in Newly Diagnosed Myeloma Patients: a Possible Mechanism of ESAs Association with Reduced Survival Rates.

Abstract 4873

Angiogenesis plays a significant role in the biology of multiple myeloma (MM). Erythropoiesis stimulating agents (ESAs) have been recently associated with reduced survival in a subset of cancer patients who receive ESAs, including MM but the etiology for this correlation has not been sufficiently explored. It is known that the endothelial cells produce angiogenic factors, promote the growth and survival of MM cells and carry erythropoietin receptors which in hypoxic conditions they transport the signal for their own proliferation and expansion under the influence of the endogenous erythropoietin. The aim of this study was to investigate the possible impact of ESAs administration on post-therapy angiogenesis. We studied 84 newly diagnosed MM patients (47M/37F; median age: 65 years, range: 39-82 years) who underwent conventional anti-myeloma therapy: 62 patients received VAD (53 of whom within the context of the randomized study VAD vs. TVAD, conducted by the Greek Myeloma Study Group) and 22 patients received MP. Fifty-two patients received ESAs for at least 8 weeks (ESA group), while 32 did not receive ESA (non-ESA group). MVD was assessed in bone marrow biopsies at baseline and at the time of best response by using monoclonal antibodies targeting CD34. The number of microvessels expressing the CD34 antibody was counted by two experienced pathologists through a grid at a magnification of 400x and was finally divided to the number of the high power fields used for screening the whole marrow surface. The counts were finally expressed as number of vessels per mm² area of the involved marrow. Fifteen individuals with normal findings in the bone marrow were used as controls. Furthermore, the following cytokines that are involved in the angiogenesis process in MM were measured in the serum of both patients and controls on the day of the trephine biopsy performance: VEGF, bFGF, TGF-b, IL-6, soluble IL-6R (sIL-6R), IL-1b and TNF-α, using an ELISA methodology (R&D, Minneapolis, MN, USA). Patients characteristics between the ESA and non-ESA groups at baseline were well balanced except of Hb which was, as expected, significantly lower in the ESA-group (p<0.001). The median follow-up was 84 months (range 5-154). The median number of baseline MVD in the ESA group was 18.5/mm² (range: 1-29.3) and in the non-ESA group 17.7/mm² (range: 2-28.5; p=NS) and was higher compared to controls (median 1.2/mm², range: 0-9; p<0.001 for both comparisons). The post-therapy MVD in the two groups were 16/mm² (range: 1.8-26) for ESA and 12.8/mm² (range: 2-29) for non-ESA group, respectively (p=0.03); the % reduction between baseline and post-therapy value was significantly greater in the non-ESA group (non-ESA group: 24.9%, range -36% to +76.6%, ESA group: 14.5%, range -410% to +85.6%, p=0.04). Myeloma patients before treatment had increased serum levels of VEGF (p=0.029), bFGF (p=0.012), IL-6 (p=0.007) and sIL-6R (p=0.047) compared to controls and showed no differences between ESA and non-ESA groups and no alterations post-therapy. Post-therapy, MVD positively correlated with the baseline MVD and baseline β2-microglobulin and negatively correlated with baseline Hb, response to treatment and PFS (p<0.05). In the ESA group but not in the non-ESA group, post-therapy MVD was negatively correlated with response to treatment (p<0.05). In the multivariate analysis, age and post-therapy MVD were the only independent predictors for OS (p=0.04 and p=0.005, respectively; Hz ratio for post-therapy MVD: 1.2, 95% CI: 1.04-1.28). In the ESA group, the multivariate analysis showed that post-therapy MVD >14/mm² was the only independent predictor for survival (p=0.04; Hz ratio 0.136, 95% CI: 0.02-0.9) whereas in the non-ESA group, post-therapy MVD did not show any significant prognostic value, either used as a continuous or a dichotomous variable. The median PFS for patients with post-therapy MVD >14/mm², was 13 months (95% CI: 8.5-17.5) and for patients with MVD <14/mm² was 33 months (95% CI: 25-41; p=0.001). The median OS in patients with MVD >14/mm² was 37 months (95% CI: 29-45) and for those with MVD <14/mm² was 63 months (95% CI: 50-75; p=0.04). These results suggest that ESAs may negatively influence the post-therapy MVD. In the ESA group MVD negatively correlated with disease response and MVD >14/mm² was the only independent predictor for OS. These findings could partially explain the possible association of ESAs with reduced survival rates in newly diagnosed MM patients. Prospective studies are required in order to fully investigate this current issue.