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Plasma Exchange in Multiple Myeloma
IN RESPONSE:
My coauthors and I concur that, on closer observation of our data, more questions are found than answers. We hope that most careful readers would experience this phenomenon when looking closely at data from other randomized, controlled trials. Dr. Leung raises the issue of an absence of renal biopsies and refers to an autopsy study published in 1990 (1), which indicated that 37% of patients with myeloma had light-chain or cast nephropathy and 11% had amyloidosis. Fewer than 20% of patients with myeloma have a clinical picture of acute renal failure and heavy proteinuria at diagnosis. As indicated in our Methods and Discussion sections, these are the entry criteria for patients who were enrolled in our study. Two pathologic studies (referenced in our paper) have shown that this clinical picture of progressive or acute renal failure has a 77% to 97% incidence of light-chain or myeloma cast nephropathy (2, 3). Dr. Leung asks why death was included as the primary outcome measure in our study, which was initiated in 1998. The decision to include death was based on the previously published findings of Zucchelli and associates (4). In this small randomized, controlled trial, which involved 29 patients, the plasma exchange group experienced a significant reduction in mortality attributable to the plasma exchange procedure (4). We agree with Dr. Leung that at this time plasma exchange cannot decrease the tumor burden, increase the CD4 cell count, or improve the cytogenetic factors that have been shown to be prognostic in this population.
As a nephrologist and as a physician, I concur that it is important for nephrologists and other physicians to focus on improving quality of life for patients with acute renal failure at the onset of myeloma. My coauthors and I also believe that our role in this disease is clear: to carry out, wherever possible, interventions that are more likely to benefit and less likely to harm our patients based on the best available evidence to date. We strongly encourage all of our colleagues to actively participate in randomized, controlled trials to provide clearer treatment options.
Article and Author Information
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Potential Financial Conflicts of Interest: None disclosed.
