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Keywords:

  • relapsed/refractory multiple myeloma;
  • pegylated liposomal doxorubicin;
  • bortezomib;
  • monoclonal (M) protein;
  • response rapidity

Abstract

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONFLICT OF INTERESTS DISCLOSURES
  7. REFERENCES

BACKGROUND:

A rapid and early monoclonal (M) protein response during initial therapy in patients with multiple myeloma had been identified as a predictor of superior long-term outcome in some—but not all—studies.

METHODS:

To determine if the parameter of M protein reduction was of value in the relapsed and/or refractory setting, retrospective landmark analyses were performed at the end of cycles 2 and 4 of a phase 3 study, which randomized such patients to receive bortezomib alone or pegylated liposomal doxorubicin (PLD) with bortezomib.

RESULTS:

Compared with a <25% reduction in M protein at the landmark time point, patients with a 50% to <75% reduction after cycle 2 had a significantly lower hazard ratio (HR) for time to progression (HR = 0.41; 95% confidence interval [CI], 0.26-0.64; P <.001), as did those with a ≥75% reduction (HR = 0.26; 95% CI, 0.15-0.45; P < .001). In all of these groups, PLD + bortezomib provided superior outcomes to bortezomib alone, and did so without an increase in the risk of adverse events overall and with a predictable toxicity profile.

CONCLUSIONS:

These analyses supported the possibility that a robust early M protein response is a good prognostic factor for long-term outcome of myeloma patients with relapsed and/or refractory disease receiving bortezomib or PLD + bortezomib. Cancer 2011;. © 2011 American Cancer Society.

Approximately 20,180 new cases of multiple myeloma will be diagnosed in the United States during 2010, and approximately 10,650 people will die of the disease during the same period.1 In part due to the availability of new therapies for multiple myeloma, 5-year survival rates and median survival have increased substantially over the past several decades. The latter, for example, has improved from approximately 2 to 3 years from the time of diagnosis in 1985 through 1998, to approximately 5 to 7 years for patients diagnosed in 2005.2, 3 Although multiple myeloma remains incurable, novel and rationally designed regimens such as pegylated liposomal doxorubicin (PLD; DOXIL®) and the proteasome inhibitor bortezomib (VELCADE®) appear to be improving outcomes in patients with relapsed and/or refractory disease as well. Indeed, in a phase 3 randomized trial comparing PLD + bortezomib with bortezomib alone in this patient population, PLD + bortezomib improved time to progression (TTP) from 6.5 months with bortezomib alone, to 9.3 months in patients treated with the combination.4 Moreover, therapy with PLD + bortezomib improved the complete plus very good partial response rate, the response duration, the progression-free survival, and the overall survival compared with single agent bortezomib.

Prognostic factors, such as advanced age, low serum albumin, greater number of prior therapies, and increased β2-microglobulin (β2M) levels have been recognized to unfavorably affect treatment outcomes in both front-line and relapsed settings and impact subsequent treatment choices.5 Other factors may also influence the choice of salvage therapy in relapsed/refractory multiple myeloma, including various disease characteristics such as the monoclonal (M) protein burden. Several studies have suggested that there is a positive relationship between rapidity of response, as measured by the reduction in M protein, and outcomes in patients with newly diagnosed multiple myeloma. For example, Ross et al noted that those patients who achieved at least a partial response after 1 cycle of infusional vincristine and doxorubicin with oral dexamethasone (VAD) had a superior event-free survival compared with those with lesser quality responses.6 Similarly, Schaar et al reported that at least a 30% reduction in the M protein, and especially a 40% reduction after 1 cycle of melphalan and prednisone (MP), predicted for superior survival.7 Thus, an early response to induction therapy in multiple myeloma may benefit long-term outcome measures and may result in an improvement in symptom burden. To investigate the possibility that a relationship between rapid response and outcomes is also present in the relapsed and/or refractory setting, we retrospectively evaluated the impact of an early reduction in the M protein in the phase 3 trial of PLD + bortezomib versus bortezomib alone in patients with relapsed and/or refractory multiple myeloma.4

METHODS

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONFLICT OF INTERESTS DISCLOSURES
  7. REFERENCES

Study Treatment and Endpoints

Full details of the primary study design, protocol, and treatment have been previously described.4 Briefly, patients naïve to bortezomib who had measurable disease, had progressed after ≥1 line of therapy, or were refractory to initial treatment were randomized after stratification by β2M levels and response to initial therapy. The intent-to-treat (ITT) population received PLD at 30 mg/m2 as a 1-hour or longer intravenous (IV) infusion on Day 4 and bortezomib at 1.3 mg/m2 on Days 1, 4, 8, and 11 of every 21-day cycle (n = 324), or bortezomib alone at the same dose and schedule (n = 322). Treatment continued until disease progression or unacceptable toxicity occurred or for 8 cycles, although patients who were still responding after 8 cycles could continue, provided that treatment was tolerated. The primary efficacy endpoint was the TTP, and secondary endpoints included response rate and safety. Assessments of the latter included adverse event reports, changes in clinical laboratory findings, and cardiac function tests (multiple gated acquisition scan/echocardiogram/electrocardiogram).

Post-hoc Landmark Analyses of M Protein (Early Response)

The percentage decrease from baseline in M protein was evaluated post-hoc using landmark analyses at the end of cycles 2 and 4. Patients were categorized into 4 groups by reduction in M protein at the landmark time points. Patients included in the landmark analyses must have: 1) had baseline M protein ≥1.0; 2) had end of cycle 2 (or cycle 4) M protein data; 3) had dose intensity >0 for cycle 2 (or cycle 4); and 4) not progressed or been censored by study day used for M protein data at end of cycle 2 (or cycle 4). Using a Cox proportional hazard model, TTP was evaluated by treatment and by the 3 groups with ≥25% M protein reduction compared with the group with <25% M protein reduction.

RESULTS

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONFLICT OF INTERESTS DISCLOSURES
  7. REFERENCES

A total of 199 patients receiving PLD + bortezomib and 205 patients receiving bortezomib alone were included in the landmark analysis at the end of cycle 2, while 116 patients receiving PLD + bortezomib and 129 patients receiving bortezomib alone were included in the landmark analysis at the end of cycle 4. Because our interest was focused on the early responders, the results below focus on the landmark analyses at the end of cycle 2.

Efficacy

Regardless of the treatment assignment, a decrease in the risk of TTP was observed in patients with a greater reduction in M protein (Table 1). At the cycle 2 landmark analysis, the risk reduction was significant for the 50-<75% M protein reduction group (approximately a 60% risk reduction) and for the ≥75% M protein reduction group (approximately a 75% risk reduction). At the cycle 4 landmark analysis, the risk reduction was significant for the ≥75% M protein reduction group (approximately a 60% risk reduction). PLD + bortezomib continued to be significantly superior to bortezomib alone at cycle 2 and cycle 4, even after adjusting for the % decrease in M protein. TTP was longer as M protein decreased at the end of cycle 2 and was improved for PLD + bortezomib versus bortezomib (Table 2; Fig. 1). Similar results were observed at the end of the cycle 4 landmark analysis (not shown). At the end of cycle 2, larger reductions in M protein resulted in a longer duration of response as well as in increasing percentages of patients having a complete response or partial response (CR + PR). Patients in the ≥75% M protein reduction group had the highest CR + PR rates of 97.9% and 95.0% in the PLD + bortezomib and bortezomib alone treatment groups, respectively.

Table 1. Hazards Ratios* by TTP for M Protein Reduction Groups at the End of Cycle 2 and Cycle 4 Landmarks
 Cycle 2Cycle 4
 HR (95% CI)PHR (95% CI)P
  • B indicates bortezomib; CI, confidence interval; HR, hazards ratio; M protein, monoclonal protein; PLD, pegylated liposomal doxorubicin; TTP, time to progression.

  • *

    Proportional hazards model.

B vs. PLD + B1.68 (1.19-2.37).0032.38 (1.47-3.84)<.001
M Protein reduction groups
 25-<50% vs. <25%0.84 (0.55-1.30).4380.82 (0.38-1.75).602
 50-<75% vs. <25%0.41 (0.26-0.64)<.0010.68 (0.35-1.30).238
 ≥75% vs. <25%0.26 (0.15-0.45)<.0010.40 (0.22-0.73).003
Table 2. Median TTP by M Protein Reduction Groups at the End of Cycle 2 Landmark
 PLD + B (n=199)B (n=205)
  1. B indicates bortezomib; CI, confidence interval; CR+ PR, complete response or partial response; M protein, monoclonal protein; N/E, not evaluable; PLD, pegylated liposomal doxorubicin; TTP, time to progression.

<25%, n (%)58 (29.1)63 (30.7)
 Median TTP, days (95% CI)214 (141-N/E)151 (116-242)
 Duration of response, days (95% CI)N/EN/E
 CR+PR, n/evaluable (%)1/58 (1.7%)3/63 (4.8%)
25-<50%, n (%)40 (20.1)48 (23.4)
 Median TTP, days (95% CI)221 (198-275)183 (164-230)
 Duration of response, days (95% CI)165 (123-212)172 (120-274)
 CR+PR, n/evaluable (%)11/40 (27.5%)17/48 (35.4%)
50-<75%, n (%)54 (27.1)54 (26.3)
 Median TTP, days (95% CI)338 (331-N/E)217 (197-N/E)
 Duration of response, days (95% CI)311 (297-N/E)180 (169-N/E)
 CR+PR, n/evaluable (%)48/54 (88.9%)46/54 (85.2%)
≥75%, n (%)47 (23.6)40 (19.5)
 Median TTP, days (95% CI)415 (330-N/E)261 (227-N/E)
 Duration of response, days (95% CI)394 (309-394)237 (206-N/E)
 CR+PR, n/evaluable (%)46/47 (97.9%)38/40 (95.0%)
thumbnail image

Figure 1. Kaplan-Meier estimates for time to progression by M protein reduction groups at the end of cycle 2 landmark analysis.

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Safety

The safety profiles of the 2 treatment groups, PLD + bortezomib and bortezomib alone, were comparable at the cycle 2 landmark (Table 3). Of the 404 patients evaluated at the cycle 2 landmark, 17% of patients receiving PLD + bortezomib experienced a ≥grade 3 adverse event, compared with 13% of patients receiving bortezomib alone. As expected, patients receiving PLD + bortezomib experienced more hand-foot syndrome compared with patients receiving bortezomib alone and more mucositis/stomatitis, but less peripheral neuropathy both overall, and at the grade 3 and 4 levels of severity. Overall safety profiles in this analysis were similar to the overall safety profiles for the previously reported phase 3 study.4

Table 3. Adverse Events of Interest at the End of Cycle 2 Landmark
 PLD + B (n=199)B (n=205)
n (%)All≥Grade 3All≥Grade 3
  1. B indicates bortezomib; PLD, pegylated liposomal doxorubicin.

Peripheral neuropathy77 (38.7)9 (4.5)93 (45.4)21 (10.2)
Febrile neutropenia5 (2.5)5 (2.5)3 (1.5)3 (1.5)
Bleeding/hemorrhage23 (11.6)5 (2.5)15 (7.3)2 (1.0)
Mucositis/stomatitis43 (21.6)4 (2.0)9 (4.4)1 (0.5)
Hand-foot syndrome39 (19.6)11 (5.5)00
Thromboembolic events1 (0.5)02 (1.0)1 (0.5)
Alopecia1 (0.5)01 (0.5)0

DISCUSSION

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONFLICT OF INTERESTS DISCLOSURES
  7. REFERENCES

Analyses of modern therapeutic approaches to multiple myeloma with regimens incorporating novel agents have generally supported the hypothesis that response quality predicts long-term outcomes, with deeper responses being associated with longer TTP and overall survival.2 However, there is some controversy about whether the early response rapidity is similarly predictive. Schaar and colleagues conducted a study that prospectively evaluated the relationship between survival and the rate of M protein decrement during the first cycles of therapy in 262 patients with newly diagnosed multiple myeloma who were included in a phase 3 trial (HOVON-16).7 In this study, the median M protein decrease after the first cycle of MP was 21% for IgG and 27% for IgA, and declined to <5% after 4 cycles. A survival advantage was seen for patients who had an M protein decrease of at least 30% after the first MP cycle, which became significant when an M protein decrease of 40% or more was reached. They also found that established prognostic parameters, including Salmon and Durie stage, serum creatinine, and hemoglobin, remained significant, leading to the conclusion that early response to MP treatment predicted for survival in multiple myeloma. However, in 2 retrospective studies by Shimizu et al, also in the front-line setting, the post-treatment nadir in M protein level was prognostic for survival outcome, but the percentage fall in M protein was not prognostic.8, 9 Moreover, van Rhee et al have reported that a rapid reduction in myeloma burden, as measured by a top-tertile reduction in the serum-free light chain levels before cycle 2, predicted for an inferior progression-free and 2-year overall survival after their induction therapy and tandem transplantation approach.10

In that these previous studies have focused predominantly on patients with newly-diagnosed disease, we sought to determine the possible impact of rapid early disease response in the relapsed and/or refractory setting. In a follow-up to the SUMMIT and CREST clinical trials, patients with relapsed and/or refractory multiple myeloma who had progressive or stable disease after single-agent bortezomib therapy were eligible to receive dexamethasone as add-on therapy. Patients with an improved response to the combination experienced a median reduction of 36.7% in M protein level, compared with a median reduction of 15.4% in responders on bortezomib alone.11 Our analyses showed that, compared with the group of patients with a less than 25% reduction, a 50% or greater, and especially a 75% or greater reduction in M protein levels at cycle 2 resulted in a significant risk reduction for time to progression. Indeed, for both the PLD + bortezomib and bortezomib alone cohorts, patients with a ≥75% M protein reduction had a TTP that was nearly double that of the group with a <25% reduction. In addition, over 90% of patients with a ≥75% M protein reduction had CR + PR, compared with less than 5% in the <25% reduction group. For all of the response categories studied, PLD + bortezomib retained its superiority to bortezomib alone in the primary study endpoint, TTP. Moreover, these benefits were not associated with a significantly higher risk for patients to develop grade 3 or higher adverse events and were associated with a predictable toxicity profile.

Limitations of the current study include: 1) this was a post-hoc analysis of a phase 3 clinical trial; 2) comparisons between M protein-reduction groups at later landmark time points may be less meaningful due to diminishing sample sizes on subsequent cycles of therapy; and 3) as the comparators in the trial were PLD + bortezomib and bortezomib alone, standard agents, such as dexamethasone,12 were not included.

Taken together, our data support the possibility that an early disease response, as defined by an at least 50% M protein reduction after cycle 2 to bortezomib alone and especially to PLD + bortezomib, identifies a group of patients with superior long-term outcomes. Moreover, these data also provide a rationale for individualization of therapy based on such early outcomes, in which those patients with at least a 50% M protein response after cycle 2, and a 75% response after cycle 4, would continue on bortezomib or PLD + bortezomib. Furthermore, this analysis provides a pathway for additional study, including the investigation of the effects of adding other agents to the combination therapy of PLD + bortezomib or to bortezomib alone when patients experience a less than adequate M protein response (<25% reduction) in early therapy.

In summary, our results suggest that the combination of PLD + bortezomib had significant benefit over bortezomib alone in extending TTP of early responders in cycle 2 and 4 landmark analyses similar to the overall study. An early response of a >50% reduction in M protein at cycle 2 resulted in a significant risk reduction for progression. These data suggest that early reductions in M protein may provide better outcomes with PLD + bortezomib combination therapy. More research is needed to investigate the effect of early responses and M protein reduction on outcomes in multiple myeloma.

CONFLICT OF INTERESTS DISCLOSURES

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONFLICT OF INTERESTS DISCLOSURES
  7. REFERENCES

The study was supported by Centocor Ortho Biotech Services, LLC, Horsham, Pennsylvania. Dr. Bladé is a consultant to Janssen-Cilag and Celgene. Dr. Sonneveld is a consultant to Johnson & Johnson. Dr. Londhe is an employee of Centocor Ortho Biotech Services, LLC. Dr. Lowery and Mr. Lantz are former employees of Centocor Ortho Biotech Services, LLC.

REFERENCES

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONFLICT OF INTERESTS DISCLOSURES
  7. REFERENCES