1 Multiorgan Transplant Unit and 2 Department of Pathology, University Hospital, Toulouse, France
Correspondence and offprint requests to: Lionel Rostaing, CHU, Multiorgan Transplant Unit, University Hospital, 1 av. Jean Pouilhès, TSA 50032, 31059 Toulouse cedex 9, France. Email: rostaing.l{at}chu-toulouse.fr
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Abstract |
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Methods. In a prospective study, we assessed long-term efficacy and safety parameters in 43 renal transplant recipients who were switched from a CNI (cyclosporin A, 65%; and tacrolimus, 35%) to sirolimus for either chronic allograft dysfunction (n = 38) or recurrent cutaneous cancers (n = 5). A kidney biopsy was done in 79% of patients prior to conversion, and showed either chronic allograft nephropathy (n = 26) or CNI nephrotoxicity (n = 7). Conversion was either abrupt or progressive, with CNI withdrawal over 3 weeks. All patients also received steroids with or without mycophenolate mofetil or azathioprin. Patient data were recorded at baseline (D0), at 1 (D30) and 6 months (D180), and at 1, 1.5 and 2 years post-conversion.
Results. After a mean post-conversion follow-up of 27±1.5 months, 58% of the patients were still on sirolimus. The survival of intent to treat patients and grafts was 95.3 and 93%, respectively. Overall, there was significant improvement in renal function, creatinine clearance increasing from 49.4±14.9 to 53±16.3 ml/min at D30 (P = 0.01), and to 54.7±20 ml/min at D180 (P = 0.01). Thereafter, creatinine clearance was not different from baseline, i.e. 54.7±21.7, 52.8±20 and 51.7±20.3 ml/min at years 1, 1.5 and 2, respectively. We divided the patients into two groups: responders (n = 29), those with an increase in creatinine clearance at 6 months post-conversion compared with D0, and non-responders (n = 14), those with a decrease in creatinine clearance at 6 months post-conversion compared with D0. In univariate analysis, factors predictive of response included proteinuria at D0 and the magnitudes of the differences between D30 and D0 for serum creatinine and lactate dehydrogenase. The conversion was associated with (i) significant decreases in serum calcium, phosphorus and uric acid, and in haemoglobin levels; (ii) significant increases in serum alkaline phosphatase, total cholesterol, parathyroid hormone, and the number of patients on statin and recombinant erythropoietin therapies; and (iii) the appearance of de novo proteinuria of >1 g/day in 28% of patients (P<0.0009), which was >2 g/day in 12% of the entire cohort. Kidney biopsies in 17 patients 2 years after conversion showed the same Banff scores as observed at baseline. We identified three independent predictive factors for a renal response to the switch: absence of proteinuria, presence of antihypertensive therapy at D0 and serum lactate dehydrogenase level at D30.
Conclusion. Conversion from CNIs to sirolimus in renal transplant patients with chronic allograft nephropathy was associated with improved renal function; however, 33% of the patients developed overt proteinuria.
Keywords: anaemia; calcineurin inhibitor; chronic allograft nephropathy; creatinine; renal function; sirolimus
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Introduction |
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Patients and methods |
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Conversion protocol
Initially, we undertook a progressive conversion of patients therapies (n = 21) from CNI-based to sirolimus-based, i.e. sirolimus was given on day 1 at a loading dose of 1215 mg, then at a dose of 35 mg/day. Sirolimus trough levels were obtained weekly. The dose was adjusted to achieve trough levels of 812 ng/ml. In parallel, the CNI dose was reduced by 50% on day 1 and another 25% on day 7, before being withdrawn on day 14. As it sometimes took up to 3 weeks in some patients to obtain the targeted sirolimus trough levels, we later decided to perform an abrupt switch. Thus, 22 patients had an abrupt conversion, whereby CNI was withdrawn on day 1 and sirolimus started on day 1 with a loading dose of 1518 mg, followed by a daily dose of 46 mg/day to achieve target trough levels of 812 ng/ml. The patients other immunosuppressive drugs remained unchanged. Pneumocytis carini prophylaxis, with sulfamethoxazoletrimethoprim (400/80 mg three times weekly), was given for the 6 months following conversion. None of the patients had acute rejection during the 3 months before conversion. During the first post-conversion month, follow-up visits were scheduled weekly; later, the patients were monitored on a monthly basis until 6 months post-conversion, and then at 3 month intervals (or at shorter intervals in cases where there were adverse events or other medical reasons). Each follow-up visit included a physical examination, with blood pressure being measured, laboratory screening for sirolimus trough levels, determination of haematological (haemoglobin, white blood cell and platelet counts) and biochemical parameters [serum creatinine, sodium, potassium, calcium, phosphate, uric acid and lactate dehydrogenase (LDH)], and tests for urinary protein and liver function [i.e. aspartate (AST) and alanine (ALT) aminotransferases, -glutamyl transpeptidase (
GT), alkaline phosphatase, cholesterol and triglycerides]. Parathyroid hormone (PTH) levels were assessed at the time of conversion and then yearly. Creatinine clearance was calculated according to the Cockcroft and Gault formula. Data are given for 1 and 6 months and 1, 1.5 and 2 years post-conversion. The renal response to sirolimus was defined at 6 months post-conversion based on the stability or improvement of creatinine clearance compared with that on the day of conversion. In order to determine the factors predictive of the response to conversion from CNI to sirolimus, we identified responders as those patients in whom the difference between the creatinine clearance (CC) at 6 months post-conversion (D180CC) minus the observed value at the time of conversion (D0CC) was positive, i.e. D180CC D0CC>0. Conversely, those patients in whom the difference was negative were defined as non-responders.
Statistical analysis
The data are presented as means, SDs, medians, and minimum and maximum for quantitative variables, and the numbers of observations and frequencies for qualitative variables. Normality was tested by the KolmogorovSmirnov test.
The follow-up data were assessed by one-way analysis of variance (ANOVA) with time-repeated measures for quantitative variables: time D0 to year 2 (within-subject factor), and for the factor response (between-subject factor). If there were significant effects over time, i.e. if a P-value of <0.05 was obtained in ANOVA analysis, then paired tests were used to analyse differences between each time point. The paired Student t-test was applied to compare the differences in means between each time point. For cases where the difference was not normally distributed, the Wilcoxon signed rank paired test was applied.
The McNemar test was used to evaluate changes in qualitative variables between each time point, i.e. day 0 after conversion, day 30, day 180, year 1, year 1.5 and year 2. Sidak's adjustment for multiple comparisons was used to determine the effects of time on qualitative variables.
Predictive factors for response groups were assessed using the 2 test for categorical data or Fisher's exact test when the values were <5. Odds ratios (ORs) are reported along with 95% confidence intervals. All tests were two sided, and P<0.05 was considered statistically significant. Statistical analysis was performed using the SAS software, version 8.2.
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Results |
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Renal function
Overall, at 1 and 6 months after conversion, there were significant decreases in serum creatinine from 164.5±44 to 152.8±39 and 153.7±45 µmol/l, respectively (P = 0.02); thereafter, serum creatinine remained stable without any significant differences from pre-conversion values: 154.2±55 µmol/l at 1 year, 160±59 µmol/l at 1.5 years and 146.7±43 µmol/l at 2 years. Creatinine clearance improved significantly at 1 and 6 months post-conversion compared with baseline: 53±16.3 and 54.7±20 vs 49.4±14.9 ml/min, respectively (P = 0.01). Thereafter, it showed no statistically significant difference from baseline: 54.7±21.7 (P = 0.09), 52.8±20 and 51.7±20.3 ml/min at 1, 1.5 and 2 years post-conversion, respectively.
At the day of conversion, 82% of patients had physiological proteinuria, <150 mg/day; 13% of patients had mild proteinuria (between 150 and 500 mg/day), but the proteinuria of 5% of patients was between 500 and 1000 mg/day. There was no significant change in the pattern of proteinuria at 1 and 6 months post-conversion. This was not the case afterwards. Overall, 12 patients (28%) develop proteinuria >1 g/day. Thus, at 1 year post-conversion, the proteinuria of 19.4% of patients (seven out of 36) was >1000 mg/day (P = 0.01), and 20.6% of patients (six out of 29) had >1000 mg/day proteinuria at 2 years (P = 0.01). In addition to these, during the study period, five patients developed nephrotic-range proteinuria with impairment of renal function. Of these, at the time of conversion to sirolimus, only one patient had no proteinuria. These five patients underwent a transplant biopsy at the time of developing this proteinuria. In all cases, we found de novo lesions of focal and segmental hyalinosis, in addition to glomerular double contourswith the latter already present in the pre-conversion biopsy specimens. We did not perform follow-up transplant biopsies in these five patients. These patients were then switched from sirolimus to tacrolimus. With a median follow-up of 9 months since withdrawal of sirolimus and conversion to tacrolimus, all but one recovered from the nephrotic-range proteinuria, though they had some degree of proteinuria persisting. In addition, renal function stabilized in all patients except the one who had persisting nephrotic syndrome.
With respect to the five patients converted to sirolimus because of recurrent cutaneous cancers, renal function improved in three of them and remained stable in two. None of these patients developed de novo proteinuria.
Renal transplant histological findings
Prior to their conversion to sirolimus, 34 patients (79%) had renal biopsies, which showed CNI-related nephrotoxicity in seven cases, CAN in six and features of both CAN and CNI-related nephrotoxicity in 21. The median chronic Banff score for these 34 renal biopsies was c.g 0; c.i 1; c.t 1; m.m 1. Repeat graft biopsies were done in 17 patients (50%) at an average of 2 years after conversion. Their median chronic Banff scores remained absolutely unchanged at c.g 0; c.i 1; c.t 1; c.v 1, m.m 1, being stable in 11 cases, improved in three and deteriorated in three. To identify the factors that might be associated with the response to the conversion to sirolimus at D180, we used univariate analysis and took into account all of the variables from D0, D30 and D180, and, for each variable, the differences between D30 and D0, and between D180 and D0, i.e. D30 D0 and D180 D0. Table 1 shows the variables for which P is <0.1. When comparing these results between non-responders and responders, the responders (67.4% of patients) had a significant improvement in serum creatinine over D0 (P = 0.038) as well as an improvement in creatinine clearance, although the difference did reach a level of significance (P = 0.08) (Table 1). In addition, the rate of proteinuria at day 0 (P = 0.018), as well as LDH levels at 1 month post-conversion (P = 0.008) were significantly lower in the responders compared with the non-responders (Table 1). In the multivariate analysis, we identified three independent factors that predicted a positive response to the conversion from CNI to sirolimus: the absence of proteinuria at day 0, the concomitant use of antihypertensive drugs at day 0 and the level of LDH at 1 month post-conversion (Table 2). The association of predicted probabilities and observed responses was 87.2%.
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Biochemical parameters
There was no significant change in serum sodium and potassium, but there were significant decreases in serum calcium, phosphate and uric acid, and significant increases in alkaline phosphatase and PTH (Table 3). With respect to haematological parameters, by 1 month after conversion there was a significant decrease in haemoglobin, which remained stable afterwards, but at the expense of a significant increase in the numbers of patients requiring de novo recombinant erythropoietin (rEpo) therapy (Table 3). At D0, only four patients (9.3%) were on rEpo therapy; by 1 and 2 years post-conversion, 39.5 and 32.1% of patients, respectively, required rEpo therapy to maintain their haemoglobin levels within the normal range (P = 0.0003). Also, after conversion, there was a statistically, but not clinically, significant decrease in white blood cell count.
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Discussion |
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There have been other reports of conversion from CNI-based immunosuppression to sirolimus in chronic renal transplant patients. Dominguez et al. [9] studied 20 patients, including 12 with CNI toxicity, over a short follow-up of 6 months. They found a significant improvement in renal function. Citterio et al. studied 19 renal transplant patients with progressive allograft dysfunction; their conversion was abrupt, and renal function stabilized or improved in 57% of them [10]. Finally, Amm et al. reported on 57 patients; after conversion from a CNI to sirolimus, a number of patients had further renal function deterioration [12].
An increase in already present proteinuria or emergence of proteinuria are a major side effect of conversion from a CNI to sirolimus. Diekmann et al. found that, after 1 year of conversion to sirolimus, proteinuria was stable in responders, whereas it almost doubled in non-responders [11]. In our study, at conversion, nearly all patients had no proteinuria, practically speaking (<150 mg/day), with only a few percent having proteinuria ranging between 0.5 and 1 g/day. At 1 and 2 years after conversion, 19.4 and 20.6% of patients had proteinuria at >1 g/day. In addition to these, five patients developed nephrotic-range proteinuria. In all these cases, the biopsy performed at the time significant proteinuria appeared showed de novo lesions of focal and segmental hyalinosis superimposed onto pre-existing double-contour glomerular lesions. These observations have already been published in a paper describing a large series of patients treated with high doses of sirolimus initiated at the time of transplantation [13]. In long-term renal transplants, it is possible that the withdrawal of CNIs leads to hyperfiltration because these drugs have constrictive effects on the renal vasculature [14]. This might explain why those who pre-conversion had no proteinuria, despite double-contour glomerular lesions, had developed nephrotic-range proteinuria after CNI withdrawal. Thus, when renal transplant patients are converted from CNIs to sirolimus, the addition of either ACEIs or ARBs might be of interest because of their vasoconstrictive properties on glomerular efferent arterioles [15]. Because we observed de novo proteinuria after converting patients from CNIs to sirolimus, we tended, in the long-term, to substitute some antihypertensive drugs for ACEIs, ARBs or both. This explains why, at 6 months post-conversion, the number of patients on either medication was statistically greater than that at D0 or D30, despite the fact that the number of patients taking antihypertensive drugs or the number of antihypertensive drugs taken per patient remained unchanged.
We found that, after switching from CNI to sirolimus, the patients developed biochemical disorders that suggested chronic tubular toxicity. It is known that sirolimus therapy is sometimes associated with hypokalaemia [16] and it might also alter the handling of other electrolytes by renal tubules. It has been shown that impaired phosphate handling by renal allografts is aggravated under sirolimus-based immunosuppression [17]. We recently have compared the glomerular and the tubular profiles of sirolimus and everolimus in de novo renal transplant patients who were also receiving cyclosporin A. We found that, in those taking sirolimus, the renal tubular handling of phosphorus and uric acid was impaired, because the renal phosphate threshold and uric acid clearance were significantly lower than those in the everolimus group, despite similar levels of PTH (personal data). In the present study, we observed that, in the long-term, i.e. 2 years after conversion from CNIs to sirolimus, there was evidence of chronic tubular lesions, which resulted in hypocalcaemia, hypophosphataemia and hypouricaemia. The incidence of hypocalcaemia might explain the secondary increase in PTH and alkaline phosphatases.
We also found that, after conversion to sirolimus, there was a significant decrease in haemoglobin by as early as 1 month post-conversion. Thereafter, haemoglobin levels stabilized, but at the expense of significantly more frequent use of rEpo therapy in almost 50% of patients. We have shown recently that amongst the most powerful independent factors predicting anaemia within the first year post-transplantation are sirolimus therapy and renal function [18]. Recently, Augustine et al. reported a prevalence of anaemia of 31% in patients on mycophenolate mofetil-based compared with 57% on sirolimus-based therapy in de novo renal transplant patients at 1 year post-transplantation. In a multivariate analysis, the factors predictive of anaemia at 1 year post-transplantation were higher recipient age, female gender, older donor age, chronic infection, decreased renal function at 12 months, and sirolimus therapy [19]. Sirolimus has been shown to block, through mTOR inhibition, S6 kinase activity, and consequently to impair cell replication in erythroid cell lines, because S6 kinase plays a role in mRNA translation in the cell. The net effect is altered erythroid cell development and the resulting anaemia [20].
In summary, conversion from CNIs to sirolimus in renal transplant patients with CAN was associated with improvement in renal function in 29 patients (67.4%); however, 28% of patients developed overt proteinuria. Sirolimus therapy is moderately tolerable; 30.2% of patients withdrew and one-third of patients developed anaemia, which required supportive therapy with darbopoetin. Finally, we were able to identify three independent factors predictive of the renal response to the switch. These were the absence of proteinuria, the presence of antihypertensive therapy at the time of conversion and serum lactate dehydrogenase level at 1 month. A prospective randomized study with kidney biopsies prior to and after the coversion is warranted in order to identify those patients with CAN who might benefit most from this conversion.
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Acknowledgments |
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Conflict of interest statement. None declared.
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References |
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