The invention relates to a foamable ethylene polymer composition comprising at least one antioxidant, at least one process aid and at least 80 wt % of a peroxide-treated ethylene polymer composition. The foamable ethylene polymer composition has melt strength of at least 2 cN, a density of 940 to 970 kg/m3, and dissipation factor measured at 1.9 GHz of 50-80−10−6. The invention further relates to a process for making such a foamable ethylene polymer composition, and use of the foamable ethylene polymer composition in a foamed cable insulation.