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Prepublished online as a Blood First Edition Paper on September 5, 2002; DOI 10.1182/blood-2002-06-1698.
CLINICAL OBSERVATIONS, INTERVENTIONS, AND THERAPEUTIC TRIALS
From the Division of Hematology and Internal Medicine
and the Division of Biostatistics, Mayo Clinic, Rochester, MN.
This study examined the prognostic value of circulating peripheral
blood plasma cells (PBPCs) in patients with primary systemic amyloidosis (AL). A sensitive slide-based immunofluorescence technique was used to assess 147 patients for circulating PBPCs. Circulating monoclonal plasma cells were quantified as a percentage of circulating cytoplasmic immunoglobulin-positive cells (PBPC%). The absolute circulating plasma cell count was also determined. When analyzed retrospectively, 24 (16%) of 147 patients were found to have
detectable circulating PBPCs. Overall survival for patients with high
PBPC%'s (> 1%) was poorer (median survival, 10 vs 29 months;
P = .002). Similarly, overall survival for
patients with high PBPC counts (> 0.5 × 106/L) was
significantly poorer (median, 13 vs 31 months;
P = .003). Increased percentages of bone
marrow plasma cells (BMPC%; P = .0004),
increased levels of serum Primary amyloidosis (AL) is a monoclonal plasma
cell disorder characterized by the excess production and deposition of
monoclonal immunoglobulin light chain fragments in various organs and
tissues of affected individuals. The pattern of organ involvement
varies among individuals and determines the clinical presentation of the patient. The 4 most common presentations of AL patients are nephrotic-range proteinuria with or without renal insufficiency, congestive heart failure resulting from restrictive cardiomyopathy, unexplained hepatomegaly, and idiopathic peripheral
neuropathy.1 Although the clinical course depends on the
dominant organ system involved by amyloidosis, the cause of death in
most patients is cardiac related and usually reflects the extent of
cardiac involvement by amyloidosis.1 Patients with
AL can respond to chemotherapy; however, the overall prognosis for
these patients is poor, with median survival for nonresponding patients
reported to be a year.2 Response to conventional
alkylating agent-based chemotherapy is slow (median time to response
is a year) and seen in a minority of patients (18%), but responders
have improved survival (90 months vs 12 months).2
Approximately 10% of AL occurs with concurrent multiple myeloma (MM),
that is, with anemia caused by plasma cell replacement of bone marrow
hematopoietic precursors or lytic bone lesions. Similarly, a fraction
of patients with clinical MM have associated AL. A minority of AL cases
have 30% or more plasma cells in the bone marrow in the absence of
clinical features of MM. Evolution of MM from AL is rare, occurring in
6 of 1600 patients over 20 years.3
The presence of high levels of circulating plasma cells has independent
prognostic value in MM.4 We have previously shown that
circulating monoclonal plasma cells are detected in a subset of
patients with AL.5 The purpose of this retrospective study was to determine the prognostic significance of increased levels of
circulating monoclonal plasma cells in AL.
Patients were considered to have AL if they had biopsy-proven
amyloid tissue deposits associated with a monoclonal plasma cell
population in the bone marrow or evidence of a monoclonal (M)
protein in serum or urine. Clinical MM was defined as the presence of
an M protein in serum or urine associated with lytic bone disease or
30% or more monoclonal plasma cells in the bone marrow.
Patients and data collection
Detection and quantification of circulating plasma cells
Statistical methods Patients were followed up until death or, for those still alive, until most recent follow-up. The major goal of this study was to retrospectively review the correlation of circulating PBPCs with patient overall (all-cause) survival. Patient characteristics, including age, serum albumin level, serum creatinine level, serum 2-microglobulin level, serum C-reactive protein level,
serum M protein level, PBPC count, PBPC%, PCLI, bone marrow plasma
cell percentage (BMPC%), and dominant cardiac amyloid
involvement, were examined for their ability to predict overall
survival. Cutoffs or threshold values for the various parameters were
defined on the basis of known normal ranges or previously published
results. Survival curves were generated by the Kaplan-Meier method, and differences between pairs of curves were analyzed by the log-rank test.
The interaction between each potential patient characteristic or
prognostic factor and its effect on survival was analyzed by the Cox
proportional hazards model. All analyses were performed with the
StatView software package from SAS (Cary, NC).
The 147 patients ranged in age from 37 to 86 years. Patient
characteristics are listed in Table 1.
Follow-up data were available for all patients.
In our series, 20 of 147 patients had concurrent MM. Fourteen patients had 30% or more bone marrow plasma cells (BMPC%). Six patients were classified as having MM on the basis of lytic bone disease. AL patients with concurrent MM have a worse prognosis than other AL patients (median survival of 14 months vs 32 months; P = .02), and a higher proportion had detectable circulating PBPCs (30% vs 13%). Of the subset of patients with PBPC%'s of 2% or more, 50% had clinical MM, compared with 12% of patients with PBPC%'s lower than 2% (P = .008). Survival Of the 147 patients, 109 died; the median overall (all-cause) survival of the cohort was 25 months. By univariate analysis (Table 2), overall survival was significantly poorer for patients with high PBPC counts (> 0.5 × 106/L), with median survival of 13 months vs 31 months (P = .003; Figure 1A). Similarly, patients with a high circulating PBPC% (> 1%) had poorer overall survival (median survival of 10 months vs 29 months; P = .002; Figure 1B). As a dichotomized variable (cutoff of 2.7 µg/mL), 2-microglobulin level was significant for survival
(P = .04; Figure 1C), as was dominant cardiac
amyloid involvement (P = .03; Figure 1D).
Patients with increased bone marrow monoclonal plasma cell burden
(BMPC% > 10%) also had poorer survival, with median survival of 14 vs 33 months (P = .04; Figure 1E). Age, sex,
serum C-reactive protein level, serum albumin level, serum creatinine
level, serum M protein level, and bone marrow PCLI were not significant
for survival. By multivariate analysis, high circulating PBPC count and
BMPC% were significant determinants of survival (Table
3).
Nine of the 147 patients underwent SCT. When these patients were excluded from the analysis, the study findings were unchanged. In the remaining 138 patients, overall survival was poorer in those with high circulating PBPC%'s (> 1%), with median survival of 10 months vs 31 months (P = .02). Additionally, when patients with concurrent MM were excluded from the analysis, the effect of high PBPC count on survival remained unchanged. Of 127 AL patients without MM, those with high circulating PBPC%'s (> 1%) had significantly poorer survival (10 months vs 32.5 months; P = .04). Survival analysis using various combinations of prognostic factors A combined consideration of PBPC% and BMPC% separated patients into high-, intermediate-, and low-risk groups, with median survival times of 10, 15.5, and 37.5 months, respectively (P = .0003; Table 4; Figure 2).
There is a substantial basis for the study of circulating monoclonal plasma cells in AL. The number and labeling index of circulating clonal PBPCs are markers for disease activity and have been shown to be prognostic for the clinical course of smoldering MM7 and MM.4,6,8 In MM, PBPC% and bone marrow PCLI can be used to reliably stratify patients into low-, intermediate-, and high-risk groups, with statistically significant differences in survival.4 Although the presence of a circulating clonal plasma cell population has been demonstrated previously in AL patients by several different techniques, the prognostic significance of this finding has been unclear.5,9 The cause of death in most patients with AL is cardiac related, with
clinical outcome determined by the extent of cardiac involvement with
amyloidosis.1 In a previous multivariate analysis for prognostic factors in AL, presence of symptomatic congestive heart
failure emerged as the most powerful adverse predictor for survival.10 Serum Our study is a retrospective analysis of 147 patients with AL (of 694 patients evaluated between 1991 and 1996) who underwent testing for circulating PBPCs, on a random basis, at presentation. The results indicate that, in this group of patients, high levels of circulating PBPCs are associated with poorer survival. This establishes a new prognostic factor for AL patients at diagnosis. A lower PBPC% threshold (> 1% vs > 4%) is associated with worse prognosis in AL patients than in MM patients.4 Consistent with previous reports,5,9 circulating PBPCs were detected in a significantly smaller proportion of patients with AL than had previously been reported for MM patients (16% vs 80%).4 Median absolute PBPC count (0 vs 4.4 × 106/L) and PBPC% (0% vs 6.0%) were lower in newly diagnosed AL patients than in newly diagnosed MM patients.4 These likely reflect the lower proliferative capacity of the neoplastic plasma cell clone in AL than in MM. This study confirms the prognostic value of bone marrow plasma
cell burden (BMPC%), serum Detection of circulating plasma cells in AL may facilitate treatment decisions, which are frequently difficult in these patients. Myeloablative chemotherapy with stem cell rescue has been offered to a highly select group of AL patients. Further studies are needed to establish whether, as seen in MM, monitoring of PBPCs helps determine the appropriate time to harvest peripheral blood stem cells and select candidates for stem cell rescue.13,14 Such studies will also establish whether, as in MM, the presence of circulating PBPCs predicts a shorter relapse-free survival.15 Additionally, eradication of circulating PBPCs may serve as a surrogate marker for response to therapy in a minority of AL patients. Although roughly 10% of AL patients have concurrent MM and vice versa, such a diagnosis is frequently difficult to establish. Some patients are diagnosed primarily with MM with lytic bony lesions and are incidentally found to have amyloid deposits on tissue examination, whereas the situation is reversed in the remaining patients with concurrent disease. Although AL patients with concurrent MM have a greater likelihood of having circulating PBPCs and have a worse prognosis than AL patients without concurrent MM, exclusion of this patient subset did not change the overall study conclusions. Our study indicated that the subgroup of patients with 2% or more circulating PBPCs had a higher likelihood of concurrent MM. In summary, we found that a high level of circulating clonal plasma cells was associated with a poorer prognosis in AL, as has been found for other plasma cell dyscrasias. This is likely due to a higher proliferative rate of the abnormal plasma cell clone and, consequently, a propensity to involve the peripheral blood.
Submitted June 10, 2002; accepted August 27, 2002.
Prepublished online as Blood First Edition Paper, September 5, 2002; DOI 10.1182/blood-2002-06-1698.
Supported by grants CA85818 and CA62242 from the National Cancer Institute, Bethesda, MD. S.V.R. and R.F. are supported in part by Leukemia and Lymphoma Society Translational Research Awards.
The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 U.S.C. section 1734.
Reprints: S. Vincent Rajkumar, Division of Hematology and Internal Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905; e-mail: rajks{at}mayo.edu.
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© 2003 by The American Society of Hematology.
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L. F. Porrata, M. A. Gertz, M. R. Litzow, M. Q. Lacy, A. Dispenzieri, D. J. Inwards, S. M. Ansell, I. N.M. Micallef, D. A. Gastineau, M. Elliott, et al. Early Lymphocyte Recovery Predicts Superior Survival after Autologous Hematopoietic Stem Cell Transplantation for Patients with Primary Systemic Amyloidosis Clin. Cancer Res., February 1, 2005; 11(3): 1210 - 1218. [Abstract] [Full Text] [PDF] |
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