myeloma prognosisasymptomatic myeloma prognosismalignant myeloma prognosissmouldering myeloma prognosissmoldering myeloma prognosisstage 2 myeloma prognosisplasma myeloma prognosismetastatic multiple myeloma prognosisaggressive multiple myeloma prognosissmoldering multiple myeloma prognosisstage 4 multiple myeloma prognosisplasma cell myeloma prognosis