Treating Lupus Nephritis: Does Ethnicity Play a Role?
- Current therapies for lupus nephritis in an ethnically heterogeneous cohort
Journal of Rheumatology, Volume 36, Issue 2, February 2009, pp. 298–305
What is the topic?
This is another study looking at the immunosuppressive drugs cyclophosphamide (CY) and mycophenolate mofetil (MMF) for treatment of lupus nephritis (LN). (See Mycophenolate mofetil versus cyclophosphamide for induction treatment of lupus nephritis, Journal of American Society of Nephrology, Volume 20, Issue 5, May 2009, pp. 1103–1112).
What did the researchers hope to learn?
The researchers wanted to compare outcomes of patients treated with MMF or CY for lupus nephritis, for both induction and maintenance therapy.
Who was studied?
A group of 99 patients who were treated for lupus nephritis (LN) between January 2000 and February 2007 were followed for this study. The patients were either treated at New York University Medical Center (NYUMC) or had their records sent by their doctors for review by the lupus team at NYUMC. All of the patients had been followed at least six months after they had a kidney biopsy -- a procedure in which a small amount of tissue is removed from the kidney through a fine needle and examined under a microscope to see whether lupus is active in the renal system, what type of kidney inflammation might be present, and the degree of kidney damage that has occurred. Eighty-five of the patients were women (86%), and most were from ethnic minority groups -- 22 (24%) African American, 31 (34%) Hispanic, and 26 (28%) Asian. Forty-eight had been treated with MMF and forty-five received CY as induction therapy for their LN.
How was the study conducted?
This was a retrospective study, which means the researchers went back and looked at the records of patients who had been treated in the past. These were “real-life” treatment situations, where the patients’ doctors chose the medicine they felt would work best for their patients. The researchers compared the treatments and the outcomes for the 48 patients who had been treated with MMF for induction therapy for LN with those of the 45 who received CY. Among the factors they looked at were whether or not the patient had private insurance, and the classification of LN of each patient. (The different classifications are determined in part by the type and amount of tissue damage and whether there is scarring.)
What did the researchers find?
The researchers found differences between the patients who had received MMF and those who had received CY. If patients had a particularly serious kind of nephritis (CLASS IV LN), more were treated with CY (79%) than MMF (55%). A higher percentage of patients treated with MMF had private health insurance (79%) than the CY patients (49%).
The researchers also saw a higher rate of response for patients who had MMF as induction therapy (34 of 48 patients, 71%) than those who received CY (18 of 45, 40%). Even after factoring in the degree of LN disease and other clinical differences among the patients, the researchers saw that overall there was more improvement with MMF treatment than with CY treatment.
There were significant differences in response to treatment, based on ethnicity or race. All 11 of the Asian patients with proliferative nephritis responded to MMF; in contrast, fewer than half of the Hispanic patients (5 of 11, 45%) responded. For CY induction therapy, six of the 10 Asian patients with proliferative nephritis (60%) responded versus only one of 11 (9%) of the Hispanic patients. Hispanic patients made up 60% of all of the patients who did not respond to MMF. However, apparently they still did better on MMF than on CY.
Of the 52 patients who responded to induction therapy, the researchers followed 47 during their maintenance period (the other five had only just completed induction therapy when the study ended). Most of the patients stayed on the same immunosuppressive medicine during the maintenance period that they had received for induction therapy—31 on MMF and 16 on CY. The researchers found no significant difference in the response during maintenance treatment between the patients who stayed on MMF and those who stayed on CY; 14 of the 31 MMF patients (38.7%) experienced at least one new kidney flare compared to six of the 16 CY patients (37.5%). As with the induction therapies, a higher percentage of the patients receiving MMF had private insurance.
What were the limitations of the study?
In a retrospective study (looking back at patients’ charts), the way that the information is collected is not as likely to provide all the information that might be important as when information is obtained going forward in time, using a protocol that makes sure all the information has been collected at the same time points. It is also easier in a prospective study to question patients each month about how many times they might have forgotten to take their pills (in the case of MMF) or even to count the number of pills that are left at the end of a month.
What do the results mean for you?
This is another study that supports the use of MMF to treat lupus nephritis, and the researchers found it might be even more likely that patients would improve with MMF than with CY. Because long-term use of CY can have serious side effects, it is good that MMF is available as an alternative.
The study also points out that there are patients who may not respond to either of these treatments, with Hispanic patients in particular at risk of poorer outcomes. This reinforces the importance of tailoring treatment specifically for each individual lupus patient and monitoring their responses closely, perhaps even using the therapeutic drug monitoring tests described elsewhere (See: Mycophenolate mofetil in patients with systemic lupus erythematosus: a prospective pharmacokinetic study, Lupus, Volume 18, Number 4, May 2009, pp. 441– 447)