Outcomes on peritoneal dialysis in patients with primary kidney disease related to multiple myeloma: A cohort study with data from the French Language Peritoneal Dialysis Registry

Welcome to AudioScholar. Today we're covering Outcomes on peritoneal dialysis in patients with primary kidney disease related to multiple myeloma: A cohort study with data from the French Language Peritoneal Dialysis Registry, by Jolec L and colleagues, published in Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis.

Kidney impairment is a common and serious complication of multiple myeloma, with a significant number of patients progressing to end-stage kidney disease requiring dialysis. While hemodialysis is often the default, peritoneal dialysis, or PD, offers potential quality-of-life advantages by allowing for home-based therapy and greater autonomy. However, there's a scarcity of data on how patients with chronic kidney disease from multiple myeloma actually fare on peritoneal dialysis, especially in the modern era of more effective anti-myeloma treatments. Clinicians are often left wondering if PD is a truly equivalent and safe option for this specific, and often sicker, patient population. This study aims to address that evidence gap by comparing the outcomes of patients on PD due to multiple myeloma with those on PD for other reasons.

To do this, the researchers conducted a retrospective cohort study using data from the French Language Peritoneal Dialysis Registry. They identified all adult patients who initiated peritoneal dialysis in France between 2010 and 2020. From this large pool, they focused on a small subgroup of 96 patients whose kidney failure was attributed to multiple myeloma. To create a comparison group, they performed a 4-to-1 random sampling of patients from the same registry who were on PD for other causes of chronic kidney disease, such as diabetic or vascular nephropathy. This resulted in a control group of 384 patients. The researchers then followed both groups to track three main outcomes: death, transfer to hemodialysis, and kidney transplantation. They used adjusted Cox regression models to compare these outcomes between the multiple myeloma group and the control group, accounting for differences in baseline characteristics like age, comorbidities, and the year dialysis was started.

First, looking at the patient characteristics at the start of dialysis, there were some notable differences. The patients with kidney disease from multiple myeloma were, on average, older and had a higher burden of comorbidities as measured by the Charlson Comorbidity Index. Interestingly, despite being a sicker group overall, they had a much lower prevalence of diabetes—only about 8 percent, compared to 34 percent in the control group. Patients with myeloma were also more likely to have been on hemodialysis before starting peritoneal dialysis, and critically, they were far less likely to be on the waiting list for a kidney transplant. Only 7 percent of the myeloma group was listed for transplant, compared to 33 percent of the control group.

Now for the main results. The central finding of the study was that, after adjusting for confounding factors, patients with kidney disease from multiple myeloma did not have a higher risk of death or technique failure compared to the control group. The cause-specific hazard ratio for death was 1.18, with a 95 percent confidence interval that crossed one, from 0.83 to 1.67, indicating no statistically significant difference in mortality. Similarly, the risk of transferring to hemodialysis was also not significantly different, with a hazard ratio of 0.73. This suggests that from the perspective of patient survival and the durability of the dialysis modality, peritoneal dialysis appears to be just as effective for patients with multiple myeloma as it is for other patients. The median time on PD was about 16 months for the myeloma group and 15 months for the control group, which is quite comparable.

However, the story was very different for kidney transplantation. Patients with multiple myeloma had a dramatically lower chance of receiving a transplant. The adjusted hazard ratio was 0.22, with a confidence interval from 0.08 to 0.59. In plain language, this means their likelihood of getting a transplant was reduced by about 78 percent compared to other patients on peritoneal dialysis. This is a stark difference and aligns with the baseline finding that fewer of these patients were on the transplant waitlist to begin with.

The study also reported an interesting secondary outcome related to peritonitis. Counterintuitively, the multiple myeloma group had a significantly *lower* risk of experiencing a first episode of peritonitis. Their adjusted hazard ratio was 0.50, meaning their risk was roughly halved compared to the control group. The authors suggest this might be partly explained by the much higher rate of diabetes in the control group, as diabetes is a well-known risk factor for peritonitis.

In assessing this study, a major strength is its use of a large, national registry, which provides real-world data on a large number of patients over a decade. This timeframe is particularly relevant as it covers the period when new, more effective anti-myeloma therapies became available, which may have improved patient outcomes. However, the study has several limitations inherent to its retrospective, observational design. The cause of kidney disease was based on clinician reporting to the registry, not on biopsy confirmation, which could lead to misclassification. The number of patients with multiple myeloma was relatively small, at just 96, which limits the statistical power to detect smaller differences or to analyze subgroups, such as causes of death. The authors noted that death related to malignancy was more common in the myeloma group, but they couldn't draw firm conclusions. Finally, as with any registry study, there is a risk of residual confounding from unmeasured variables, such as specific myeloma treatments, residual kidney function, or patient education levels, which are all known to influence dialysis outcomes.

So, what is the clinical bottom line? This study provides reassuring evidence that peritoneal dialysis is a viable and safe modality for patients with end-stage kidney disease secondary to multiple myeloma. Clinicians can be more confident that these patients are not at an inherently higher risk of death or transfer to hemodialysis simply because of their underlying diagnosis. This supports offering PD as a first-line choice, allowing patients to benefit from a home-based therapy.

The study's most striking finding, however, is the profound disparity in access to kidney transplantation. This highlights a critical area for improvement. It underscores the need for close collaboration between nephrologists and hematologists. For patients with multiple myeloma who achieve a good hematologic response to treatment, early referral and workup for kidney transplantation should be a priority. The low rates of transplantation suggest that many eligible patients may be missed. This study serves as a call to action to re-evaluate our practice patterns and ensure that patients with myeloma-related kidney disease have equitable access to this life-changing therapy.

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