Clinical implications of proteinuria in renal transplant recipients switching to rapamycin for chronic allograft dysfunction

Abstract

There is evidence that treatment with m-TOR inhibitors can be beneficial in cases of chronic renal allograft dysfunction. However, some authors have reported poor outcomes of renal function if the switch to m-TOR inhibitors is made in the presence proteinuria > 0.8 g/d. The present study sought to provide a retrospective analysis of the clinical outcome of 63 kidney recipients diagnosed with chronic allograft dysfunction whose therapy was converted to rapamycin including 35 subjects with renal biopsy-proven chronic allograft nephropathy. At the time of conversion, patients were divided into three groups: group I (negative proteinuria), group II (proteinuria between 0.3 and 0.8 g/d), and group III (proteinuria > 0.8 g/d). On conversion, 21 recipients had no proteinuria (group I). After a follow-up of 24.6 +/- 12.8 months, they showed a significant improvement in renal function (previous MDRD4 = 39.9 +/- 11.5 mL/m/1.73 m(2), current MDRD4 50.3 +/- 13.3 mL/m/1.73 m(2), P < .05). Fifteen patients (71.4%) developed proteinuria, which was generally mild (0.8 +/- 0.7 g/d) and controlled with angiotensin-converting enzyme inhibitors (42.8%). In group II (n = 18), renal function clearly stabilized after a follow-up of 23.2 +/- 14.4 months (previous MDRD4 = 30 +/- 8.8 mL/m/1.73 m(2), current MDRD4 = 37 +/- 12.2 mL/m/1.73 m(2), NS), although there was a progressive deterioration of previous proteinuria levels (previous proteinuria 0.4 +/- 0.15 g/d, current proteinuria 1.2 +/- 2 g/d, P < .05), which was more frequent and intense in patients whose treatment with calcineurin inhibitors (CNIs) was suspended (with CNI 0.9 +/- 1.7 g/d, without CNI 1.6 +/- 2.2 g/d, P < .05). Group III (n = 24) had a greater degree of renal insufficiency and a worse outcome after 25.9 +/- 18 months of follow-up, with a frank and progressive deterioration in renal function (previous MDRD4 = 38 +/- 17 mL/m/1.73 m(2), current MDRD4 = 32.5 +/- 19.2 mL/m/1.73 m(2), P < .05) and proteinuria (previous proteinuria = 1.5 +/- 0.7 g/d, current proteinuria = 2.5 +/- 2.2 g/d, P < .05) after conversion. Again, the deterioration in proteinuria was more intense in the patients whose previous CNIs were suspended (with CNI = 1.1 +/- 0.9 g/d, without CNI = 4.2 +/- 2.3 g/d, P < .05). In conclusion, for patients with chronic allograft dysfunction who do not present with proteinuria or whose proteinuria is less than 0.8 mg/d, switching to rapamycin is useful, since it clearly improves or stabilizes renal function, although there may be a discrete increase in proteinuria in the second case. However, among patients with proteinuria greater than 0.8 mg/d accompanied by a greater degree of renal insufficiency, conversion to rapamycin leads to deterioration of proteinuria levels and renal function. These data show that conversion to rapamycin in cases of chronic allograft dysfunction must be made early when there is no proteinuria or it is minimal, and that proteinuria is a predictor of the outcome of allograft function.