Multiple myeloma: why does the disease escape from plateau phase?

Multiple myeloma and persistence of drug resistance in the age of novel drugs (Review)

Multiple myeloma (MM) is a mature B cell neoplasm that results in multi-organ failure. The median age of onset, diverse clinical manifestations, heterogeneous survival rate, clonal evolution, intrinsic and acquired drug resistance have impact on the therapeutic management of the disease. Specifically, the emergence of multidrug resistance (MDR) during the course of treatment contributes significantly to treatment failure. The introduction of the immunomodulatory agents and proteasome inhibitors has seen an increase in overall patient survival, however, for the majority of patients, relapse remains inevitable with evidence that these agents, like the conventional chemotherapeutics are also subject to the development of MDR. Clinical management of patients with MM is currently compromised by lack of a suitable procedure to monitor the development of clinical drug resistance in individual patients. The current MM prognostic measures fail to pick the clonotypic tumor cells overexpressing drug efflux pumps, and invasive biopsy is insufficient in detecting sporadic tumors in the skeletal system. This review summarizes the challenges associated with treating the complex disease spectrum of myeloma, with an emphasis on the role of deleterious multidrug resistant clones orchestrating relapse.

Long-term survival in multiple myeloma is associated with a distinct immunological profile, which includes proliferative cytotoxic T-cell clones and a favourable Treg/Th17 balance

Despite improved outcomes in multiple myeloma (MM), a cure remains elusive. However, even before the current therapeutic era, 5% of patients survived >10 years and we propose that immune factors contribute to this longer survival. We identified patients attending our clinic, who had survived >10 years (n=20) and analysed their blood for the presence of T-cell clones, T-regulatory cells (Tregs) and T helper 17 (Th17) cells. These results were compared with MM patients with shorter follow-up and age-matched healthy control donors. The frequency of cytotoxic T-cell clonal expansions in patients with <10 years follow-up (MM patients) was 54% (n=144), whereas it was 100% (n=19/19) in the long-survivors (LTS-MM). T-cell clones from MM patients proliferated poorly in vitro, whereas those from LTS-MM patients proliferated readily (median proliferations 6.1% and 61.5%, respectively (P<0.0001)). In addition, we found significantly higher Th17 cells and lower Tregs in the LTS-MM group when compared with the MM group. These results indicate that long-term survival in MM is associated with a distinct immunological profile, which is consistent with decreased immune suppression.

Management of renal dysfunction in multiple myeloma

Multiple myeloma is frequently associated with renal dysfunction. In addition, it has been shown that the presence of renal failure indicates a higher tumor burden and consequently more aggressive disease. Patients who are diagnosed with renal insufficiency should be aggressively treated because reversal of renal insufficiency results in survival outcomes similar to patients who have normal renal function at diagnosis. However, the presence of renal impairment could add significantly to the morbidity of these patients and make it difficult to tolerate aggressive treatment regimens. Therefore, the treatment approach to this group of patients should include a thorough understanding of the feasibility and outcomes of the various antimyeloma treatments that are available, including newer options such as thalidomide. We recommend the following sequence of treatment in newly diagnosed patients with multiple myeloma with renal insufficiency (creatinine > 2 mg/dL): correction of hypercalcemia with full-dose bisphosphonates in patients with hypercalcemia, induction therapy that may be initiated before correction of hypercalcemia with bolus VAD (vincristine 2 mg, doxorubicin 40 mg/m(2), dexamethasone 40 mg on days 1-4, 9-12, and 17-20), and stem cell collection (cyclophosphamide 2.5-3 g/m(2)) with high-dose melphalan (140-150 mg/m(2)) with autologous stem cell transplant. Dialysis support should be considered whenever necessary for all newly diagnosed patients if renal function does not improve with aggressive initial therapy. For patients who develop renal insufficiency later in the course of the disease, therapeutic options need to be tailored to the patient's treatment history, disease status, and performance status.

Relapsed multiple myeloma

The treatment of relapsed multiple myeloma remains a challenge for clinicians. Most salvage therapies result in transient responses, with median survival from relapse ranging from 6 to 18 months. No randomized trials comparing salvage therapies have been performed. In the absence of a "gold standard" salvage therapy, relapsed patients should be considered for clinical trials. In light of the recent observation that thalidomide alone brings about a 30% to 35% response rate with manageable toxicities, this is the most promising single agent available to treat relapsed disease. The maximum effective dose appears to be 400 mg/d; virtually all responses are evident within 2 months of starting therapy. Combination therapy of thalidomide with pulse dexamethasone or other chemotherapeutic agents has shown promise in pilot trials. Even with thalidomide-responsive disease, the response duration is brief, ranging from 3 to 6 months. Therefore, the authors recommend that patients under the age of 78 years who have acceptable physiologic organ function, chemotherapy-sensitive disease, third-party financial coverage, and adequate hematopoietic stem cells be considered for high-dose therapy with autologous hematopoietic stem cell transplant. High-dose therapy with hematopoietic stem cell transplant provides the highest response rate, response duration, and survival compared with historical controls treated with conventional therapy. Patients under the age of 70 years who have human leukocyte antigen-compatible donors should be considered for immune-based therapy using nonmyeloablative preparative regimens with allogeneic hematopoietic stem cell transplant.

Viewpoint on the impact of interferon in the treatment of multiple myeloma: benefit for a small proportion of patients?

Interferon-alpha (IFN-alpha) generally inhibits myeloma cell growth. However, a growth stimulatory effect for myeloma cells has also been reported. In patients with untreated multiple myeloma (MM) IFN-alpha, used as a single agent, produced an objective response rate ranging from 10 to 25%. In previously untreated patients: (1) the time to response is short, (2) the median duration of response is similar to the duration of response observed in patients given chemotherapy, and (3) the patients who are more likely to benefit are those with IgA myeloma type. Concerning the results of IFN-alpha given as a single agent in relapsing and resistant MM, they are poor, with a response rate ranging between 10-20%. The combination of high-dose glucocorticoids and IFN-alpha for relapsing/resistant patients produced controversial results. Some studies showed an increased response rate and/or longer survival with chemotherapy plus IFN-alpha versus chemotherapy alone in previously untreated patients. In contrast, most reports did not show a significant increase in response rate or survival benefit by adding IFN-alpha to the initial chemotherapy. Perhaps the most encouraging role for IFN in MM is as maintenance therapy in patients responding to first line treatment (ie conventional chemotherapy followed or not by high-dose intensification/autotransplantation). In spite of that, several reports failed to show longer response duration. The majority of studies have shown a modest but significant prolongation in response duration in favour of the IFN arm. However, most of these studies have failed to show a significant survival advantage with IFN maintenance. A meta-analysis, by the Myeloma Trialists' Collaborative Group in Oxford, based on the individual data from 4012 patients included in 24 randomized trials (induction and/or maintenance) has shown that IFN produced a moderate improvement in relapse-free survival and a minor improvement in overall survival. In summary, the only role of IFN in MM is as maintenance treatment after a response is achieved. However, looking at the published data, it seems that the vast majority of patients do not benefit from IFN maintenance, while a small proportion of them, in the range of 5-10%, obtain a significant prolongation in event-free survival and overall survival. Unfortunately, there are no predictive factors that can identify the patients who are likely to benefit from IFN maintenance.

Monocyte dysfunction in patients with multiple myeloma and lymphoplasmacytic disorders is related to serum paraprotein levels

We have investigated monocyte function in 30 patients with lymphoplasmacytic disorders and in 21 age and sex matched normal controls. Marked abnormalities of all facets of monocyte function were demonstrated in six patients with multiple myeloma (MM) and a single patient with Waldenström's macroglobulinaemia (WM) plus significant paraproteinaemia. Serious infection occurred in three of these patients. An inverse relationship between the level of the serum paraprotein and impairment of monocyte phagocytosis plus killing of Candida albicans was observed. Crossover studies suggested that these abnormal findings were constitutive and not reversed by removal of the serum paraprotein. The data suggest that monocyte function is constitutively abnormal in patients with MM and can be further, but reversibly, inhibited by high paraprotein levels. Further research is required to confirm these findings, ascertain whether monocyte function can be normalized using chemotherapy or growth factors, and if so, whether their tumouricidal functions could be harnessed in the treatment of this currently incurable condition.

T-helper phenotypes in the blood of myeloma patients on ECOG phase III trials E9486/E3A93

T-helper blood populations are frequently altered in multiple myeloma (MM). We measured the numbers of naive and activated cell subsets in the blood of a cohort of both previously untreated and treated MM patients. Two-colour flow cytometry to detect total CD4+, CD4+, CD4 5RA+ (naive) and CD4+, CD45RO+ (activated) subsets was then used to quantify the T-cell subsets in controls and MM patients. Previously treated MM patients either on or off treatment (n = 105) had significantly reduced (P< 0.0001) total CD4 and naive/activated cells than controls. Previously treated MM patients sampled for naive/activated cells while currently off therapy (n = 45) had no difference in the levels of CD4 and naive/activated cells compared to the currently treated patients (n = 60). However, newly diagnosed patients (n = 58) had a significantly reduced total CD4 (P = 0.023) and activated CD4 (P = 0.004), but not naive CD4 subsets, compared to controls. CD19+ cell levels above 125/microl were positively associated with higher T-helper cell levels. There was a strong positive association for better overall survival for patients with >395 CD4 cells/microl (P = 0.0001). These data indicate that MM patients at diagnosis have altered T-helper subsets, with a selective reduction in activated but not naive cells. Subsequent chemotherapy or the disease process contributes to a further reduction in CD4 cells. Importantly, the association of higher CD19+ cell levels with higher T helper cells indicates that certain myeloma patients can be identified with a more quantitatively intact immune system.

Prognostic value of serum M-protein doubling time at escape from plateau of multiple myeloma. The Finnish Leukaemia Group

A long plateau phase is one of the strongest signs predicting long survival in multiple myeloma. The kinetics of escape from the plateau is, however, poorly known, and so is its influence on subsequent survival. During a 9-yr follow-up of 432 myeloma patients the serum M-protein doubling time at first relapse was measured from serial observations in 137 cases. Univariate and multivariate analyses of pretreatment characteristics and of characteristics associated with chemotherapy were used to identify the predictors influencing on M-protein doubling time. In 65 patients the M-protein doubling time was 6 months or less and in 72 longer, with median remaining survival times of 17 and 45 months, respectively; 50% of the former group had any response to salvage chemotherapy, compared to 75% of the latter group. In univariate analysis stage and Hb were significant predictors for the M-protein doubling time. An at least 75% response was associated with short doubling time. However, the multivariate analysis left only a long preceding plateau and use of several drug combinations during primary chemotherapy as significant predictors for a long M-protein doubling time. A M-protein doubling time of 6 months or less is associated with frequent resistance to salvage chemotherapy and short remaining survival. A short doubling of the M-protein is preceded by a short plateau. The use of several drug combinations during primary chemotherapy does not jeopardize the later course of the disease. A short M-protein doubling time seems not be a chemotherapy induced phenomenon.