Posttreatment M‐Protein Nadir Level Is a Significant Prognostic Factor Associated with Survival in Multiple Myeloma

In the present study 142 patients with myeloma (102 with IgG M‐protein and 40 with IgA) treated with either VMCP (65 patients) or MMCP (77 patients) as remission induction therapy were retrospectively analyzed. Response to treatment was evaluated in terms of a more‐than‐50% fall of pretreatment M‐protein and the posttreatment M‐protein nadir. Though significantly more patients treated with MMCP achieved partial response (PR) as compared with those treated with VMCP (P=0.019) and though patients achieving PR showed a significantly longer survival than those with less responsiveness (P=0.0091), the difference in survival curves between the two treatment groups was not significant (P=0.1871). The difference in response between the treatment groups evaluated in terms of posttreatment nadir was not significant (P=0.507). Multivariate analysis identified posttreatment M‐protein nadir as a significant prognostic factor associated with survival, along with 3 other factors: sex, performance status, and hemoglobin. The lack of difference between the survival curves for patients treated with the 2 regimens despite the significantly different response rates evaluated in terms of percent fall of pretreatment M‐protein levels was considered to be due to the lack of a difference in the ability to induce a deep posttreatment nadir between the regimens. Posttreatment M‐protein nadir is an important prognostic factor associated with survival and should be included in the evaluation of the efficacy of chemotherapy.