Abstract
Introduction
Primary membranous nephropathy (pMN) is a leading cause of nephrotic syndrome (NS) in adults. Cyclophosphamide (CYC) with glucocorticoids (GCs) is recommended for high and very high-risk patients, but the optimal treatment duration and cumulative dose remain unclear. This study aimed to compare the effectiveness and safety of short-duration (SD) versus long-duration (LD) oral CYC regimens in pMN patients with NS.
Methods
We conducted a multicenter retrospective cohort study of 54 adult patients with biopsy-proven pMN treated with oral CYC in the USA and India between 2010 and 2022. Patients received either SD-CYC (≤3 months) or LD-CYC (>3 months). The primary outcome was overall remission (complete or partial) at 12 months. Secondary outcomes included complete remission (CR) rates and adverse events. Analyses were stratified by treatment duration and cumulative CYC dose.
Results
Overall remission at 12 months was similar between SD and LD groups (73% vs. 83%, p = 0.088), with a trend toward higher CR in the LD group (47% vs. 23%, p = 0.077). The SD group had more baseline chronic kidney changes, which may have impacted outcomes. By cumulative dose, patients receiving >3 g CYC had significantly higher overall remission and CR after adjustment for baseline characteristics and cumulative GC dose. Serious adverse events occurred in 18.5% of patients, with no significant differences between groups.
Conclusion
Short-term oral CYC combined with GC may be a safe alternative to LD-CYC regimens for achieving clinical remission in pMN. Although these findings align with recent evidence supporting the efficacy of low-dose CYC in pMN, well-designed clinical trials are still needed for more robust clinical validation.
Keywords: Membranous nephropathy, Nephrotic syndrome, Clinical remission, Cyclophosphamide
Introduction
Primary membranous nephropathy (pMN) is one of the leading causes of nephrotic syndrome (NS) in adults [1]. About one-third of pMN patients with NS experience spontaneous remission, 15–30% have relapsing pMN, and 14–40% of untreated patients with NS develop end-stage kidney disease over 15 years [2–4]. KDIGO 2021 guidelines recommend immunosuppressants like rituximab or cyclical cyclophosphamide (CYC) with steroids for 6 months or calcineurin inhibitors for patients with moderate-high risk of progression [5]. It is recommended to use CYC with glucocorticoid (GC) for patients with very high risk of progression, especially in setting of deteriorating kidney function. However, published evidence regarding the optimal treatment duration and cumulative dose to achieve better clinical outcomes while maintaining an appropriate safety profile is scarce. Interestingly, a recent clinical trial showed that lower doses of cyclical CYC and GC could be reasonable therapeutic alternative to standard dosing regimens [6], so comparative analysis is warranted. In this study, we aimed to evaluate effectiveness and safety profile of two regimens based on oral CYC of shorter versus longer duration in real-world clinical practice in a cohort of biopsy-proven MN patients with NS.
Methods
This is a multicenter retrospective cohort study of adult patients (age ≥18 years) with biopsy-proven pMN who received a CYC-based regimen at the Nephrology Departments from two medical centers in the USA and one in India between 2010 and 2022. Sampling was non-systematic and by convenience (consecutive patients). Patients were divided into two subgroups: a short-duration (SD) group that received CYC for up to 3 months (n = 23) and a long-duration (LD) group that received CYC for more than 3 months (n = 31). Clinical outcomes assessed 12 months after treatment initiation were analyzed based on both the duration of CYC exposure and the cumulative CYC dose, categorized as either above or below the median, corresponding to treatment durations. The flowchart of the patients included and followed up during the study is shown in online supplementary Figure S1 (for all online suppl. material, see https://doi.org/10.1159/000551814).
Treatment Protocols
The SD group (n = 23) received either oral CYC at a dose of 1.5 mg/kg/day for 3 months, with or without low-dose prednisone, or a modified Ponticelli regimen consisting of oral CYC at 1.5–2 mg/kg/day during months 2, 4, and 6, and oral prednisone during months 1, 3, and 5. Only 4 patients within SD group did not receive GC in their treatment regimen. Five patients received intravenous methylprednisolone at the beginning of months 1, 3, and 5, at the discretion of the treating physician (3 in SD group and 2 in LD group). The LD group (n = 31) received oral CYC at 2 mg/kg/day as follows: 26 patients daily and simultaneously with prednisone for 6 months, 4 patients CYC alone for 6 months, and 1 patient received cyclical regimen for 8 months. Most patients in the SD group were treated in the USA (83% vs. 17%), whereas most patients in the LD group were treated in India (77% vs. 23%) (p value <0.0001). The duration of treatment was largely determined by local practice and the expectation of achieving a sustained response, while minimizing the risk of nonresponse and relapse, particularly in settings where access to novel therapeutic agents was limited.
Outcomes and Definitions
The primary outcome was overall remission (complete remission [CR] and partial remission [PR]) 12 months after initiating treatment with oral CYC. CR was defined as reduction of proteinuria from baseline to <300 mg/day and eGFR >90% of baseline, and PR was defined as reduction of proteinuria >50% compared to baseline and to less than 3.5 g/day with stable kidney function. Secondary outcomes were the incidence of CR at 12 months and the occurrence of serious adverse events (SAEs) according to CTCAE criteria (https://dctd.cancer.gov/research/ctep-trials/for-sites/adverse-events).
Study Variables
In all patients, clinical variables assessed at baseline and during follow-up were 24-h proteinuria (g), serum albumin (g/dL), serum creatinine (mg/dL), eGFR (mL/min per 1.73 m2), hemoglobin (g/dL), platelet count (cells/mm3), white blood cell count (cells/mm3), and serum total cholesterol (mg/dL). Serum creatinine and serum albumin were measured by colorimetric methods (Jaffe method and bromocresol green or BCG, respectively). The eGFR was calculated using the CKD-EPI equation.
Statistical Analysis
Continuous variables were reported as median with 25th and 75th percentiles (Q1–Q3) due to their asymmetrical distribution, and comparisons were analyzed using the Wilcoxon rank-sum test. Categorical variables were presented as absolute and relative frequencies, with comparisons analyzed by Pearson chi-squared test or Fisher’s exact test, as appropriate. Primary and secondary outcomes were analyzed according to treatment duration and cumulative dose of CYC (CD-CYC). Relative risks (RRs) with 95% confidence intervals (95% CIs) were estimated and reported for all outcomes. Clinical response (proteinuria remission) was assessed after adjusting for relevant clinical variables such as age, sex, baseline kidney function, baseline proteinuria, and cumulative GC dose by multivariable binomial logistic regression (online suppl. material). The results were reported as odds ratios (ORs) with a corresponding 95% CI. Differences between baseline and follow-up at months 3, 6, and 12 were analyzed using the Wilcoxon matched-pairs signed-rank test. For cases where the proteinuria was expressed as urinary protein-creatinine ratio (uPCR), we used the regression equation best describing the relationship between random uPCR and 24-h proteinuria for adults [7]: proteinuria (g/day) in adults = .
For patients with reported albuminuria instead of proteinuria, we converted albuminuria to 24-h proteinuria using the formula: proteinuria = albuminuria/0.7. In patients without any available measurements of proteinuria or albuminuria, no imputation was performed. All statistical analyses and graphical presentations were conducted using Stata 16 and Microsoft Excel. A two-tailed p value of <0.05 was considered statistically significant for all analyses. We adhered to the STROBE recommendations for reporting observational cohort studies [8]. The STROBE checklist and additional details on the statistical analyses are provided in the online supplementary material.
Results
Between 2010 and 2022, 54 of 82 potentially eligible patients were included who received treatment with oral CYC for pMN. Patient demographics and clinical parameters at baseline are shown in Table 1. Median age was 67 years, 74% males, 45% Caucasians, and 53% Asians. The LD group had higher proportion of Asians (80% vs. 17%, p < 0.0001). At baseline, patients in the SD group had significantly higher rates of diabetes (p = 0.004), cancer (p = 0.01), and higher serum creatinine (1.02 mg/dL vs. 0.85 mg/dL, p = 0.03). Baseline proteinuria and serum albumin were comparable between the groups. Based on kidney biopsy findings, patients in the SD group had significantly higher tubular atrophy (29% vs. 3%, p = 0.03) and a trend for higher rates of interstitial fibrosis (18% vs. 3% p = 0.08). The median duration of treatment with CYC was 3 months (interquartiles [Q1–Q3]: 3–3) vs. 6 months (Q1–Q3: 5.5–6) (p < 0.001), and the cumulative CYC dose was 10.5 g vs. 21 g (p < 0.001) in the SD and LD groups, respectively. The median duration of treatment with GC was 3 months (Q1–Q3: 3–6) vs. 7 months (Q1–Q3: 6–11) (p < 0.001), and the cumulative GC dose was 2.7 g vs. 6.8 g (p < 0.001) in the SD and LD groups, respectively.
Table 1.
Baseline characteristics according to duration of treatment with CYC
| Characteristic | Overall cohort (n = 54) | Duration of treatment with CYC | p value | |
|---|---|---|---|---|
| SD (n = 23) | LD (n = 31) | |||
| Demographic data | ||||
| Geographical area | ||||
| USA | 26 (48) | 19 (83) | 7 (23) | <0.0001 |
| India | 28 (52) | 4 (17) | 24 (77) | |
| Male, n (%) | 40 (74) | 18 (78) | 22 (71) | 0.545 |
| Age | 67 (58–75) | 67 (60–76) | 66 (55–75) | 0.511 |
| Race, n (%) | ||||
| Caucasian | 24 (45) | 18 (78.3) | 6 (20) | <0.0001 |
| Asian | 28 (53) | 4 (17.4) | 24 (80) | |
| Afro-American | 1 (2) | 1 (4.3) | 0 (0) | |
| Diabetes mellitus, n (%) | 6 (11) | 6 (26) | 0 (0) | 0.004 |
| Hypertension, n (%) | 25 (48) | 16 (73) | 9 (30) | 0.820 |
| Autoimmune disease, n (%) | 5 (9) | 3 (13) | 2 (7) | 0.522 |
| History of cancer, n (%) | 7 (13) | 6 (26) | 1 (3) | 0.013 |
| Hypercoagulability, n (%) | 7 (13) | 14 (17) | 3 (10) | 0.160 |
| Clinical data | ||||
| Weigh (kg) | 76 (65–84) | 81 (73–89) | 74 (64–83) | 0.084 |
| Body mass index (k/m2) | 29 (25.7–34.1) | 29.4 (26–34.1) | 27.4 (21.6–31.5) | 0.247 |
| Systolic blood pressure (mmHg) | 132 (128–143) | 131 (120–140) | 134 (130–150) | 0.167 |
| Diastolic blood pressure (mmHg) | 80 (75–82) | 80 (74–86) | 80 (80–80) | 0.628 |
| Serum creatinine (mg/dL) | 0.94 (0.8–1.3) | 1.02 (0.9–1.4) | 0.85 (0.77–1.0) | 0.034 |
| eGFR (mL/min per 1.73 m2) | 83 (59–95) | 74 (50–90) | 88 (74–96) | 0.128 |
| Serum albumin (g/dL) | 2.5 (2.0–2.9) | 2.6 (2.0–3.1) | 2.4 (2.0–2.9) | 0.744 |
| 24-h proteinuria (g/day) | 6.4 (5.1–10.8) | 7.0 (5.9–10.8) | 6.3 (4.0–12.0) | 0.693 |
| Hemoglobin (g/dL) | 12.5 (11.4–13.6) | 12.3 (11.2–12.7) | 12.9 (11.6–13.8) | 0.166 |
| Total leukocytes (×1,000 per mm3) | 7.8 (6.2–8.9) | 7.2 (5.9–8.5) | 8.4 (6.7–9.1) | 0.268 |
| Platelets (×1,000 per mm3) | 248 (219–321) | 241 (206–297) | 269 (233–349) | 0.132 |
| Total cholesterol (mg/dL) | 285 (251–346) | 283 (222–311) | 288 (259–346) | 0.372 |
| Kidney biopsy data | ||||
| Glomeruli, n | 16 (10–24) | 21 (16–28) | 12 (9–20) | 0.009 |
| Percentage of sclerosed glomeruli | 2 (0–17) | 2 (0–8) | 6 (0–20) | 0.793 |
| Tubular atrophy, n (%) | 7 (14) | 6 (29) | 1 (3) | 0.033 |
| Interstitial fibrosis >25%, n (%) | 5 (10) | 4 (18) | 1 (3) | 0.080 |
| Treatment data | ||||
| Nephroprotective therapy, n (%) | | | | |
| Only ACEi | 14 (26) | 9 (39) | 5 (16) | 0.044 |
| Only ARBs | 32 (59) | 11 (48) | 21 (68) | |
| ACEi plus ARBs | 1 (2) | 0 (0) | 1 (3) | |
| ACEi or ARBs plus MRAs | 3 (6) | 3 (13) | 0 (0) | |
| Unknown | 4 (7) | 0 (0) | 4 (13) | |
| Immunosuppressive therapy | ||||
| Duration of treatment with CYC | 4 (3–6) | 3 (3–3) | 6 (5.5–6) | <0.0001 |
| Cumulative dose of CYC (g) | 18 (10.5–24) | 10.5 (8.0–13.5) | 21 (18–27) | <0.0001 |
| Cumulative dose of GC (g) | 5.3 (2.7–7.7) | 2.7 (2.0–4.2) | 6.8 (5.3–8.8) | 0.0001 |
| Duration of treatment with GC | 6 (4–10) | 3 (3–6) | 7 (6–11) | 0.0005 |
ACEi, angiotensin-converting enzyme inhibitors; ARBs, angiotensin II receptor blockers; CYC, cyclophosphamide; MRAs, mineralocorticoid receptor antagonists; LD, long duration of treatment with CYC (>3 months); NC, not computable; SD, short duration of treatment with CYC (≤3 months).
Clinical Markers and Outcomes Based on Duration of Treatment with CYC
The 24-h urine protein was 7 g in the SD group at baseline and that significantly improved to 1.5 g after 12 months, versus 6.3 g in the LD group at baseline that showed significant improvement to 0.6 g at 12 months. There was no significant difference in the starting or ending proteinuria between SD and LD patients (online suppl. Table S1; Fig. 1a), nor in the percent reduction (78% vs. 90%, p = 0.14) at 12 months. Improvement in serum albumin was comparable between the groups. Serum creatinine was significantly better at baseline and at 12 months in the LD vs. the SD groups but was well preserved in both groups when compared to respective baselines. There was no difference in groups based on eGFR at baseline (88 mL/min/1.73 m2 in LD vs. 74 mL/min/1.73 m2 in SD), but it was significantly better in LD (94 mL/min/1.73 m2) vs. SD (76 mL/min/1.73 m2) at 12 months (p = 0.004) (online suppl. Table S1). Slope of eGFR over a period of 1 year did not show any difference between the groups (+0.6 mL/min/1.73 m2 vs. +0.1 mL/min/1.73 m2 for LD and SD, respectively, p = 0.278) (online suppl. Table S2). Overall remission rates at 12 months were 73% vs. 83% (p = 0.36), CR rates were 23% vs. 47% (p = 0.08), and PR rates were 50% vs. 37% (p = 0.34), in SD vs. LD groups, respectively (Table 2). The probability of overall remission and stable GFR were similar between the groups; however, there was trend of more CR in LD group (p value = 0.077, RR: 2.1 [95% CI: 0.9–4.9]) (Fig. 1c). However, when the effect of CYC treatment duration on CR was assessed in a multivariable model adjusted for baseline proteinuria, kidney function, and cumulative GC dose, the impact of treatment duration was not significant (OR: 1.3, 95% CI: 0.9–2.1) (online suppl. Table S3). When potentially confounding variables (diabetes, history of cancer, and the severity of tubular atrophy and interstitial fibrosis) were incorporated into the regression analysis, the results were consistent with those shown in online supplementary Table S3, and none of the variables adjusted for in the model reached statistical significance (data not shown). Additionally, in our study, 4 patients, all in the SD group, did not receive GC. Three of them achieved PR, and one showed no response.
Fig. 1.
Evolution of 24-h proteinuria and probability of clinical remission according to CYC regimen. a Proteinuria levels expressed by their median and interquartile range according to the duration of CYC treatment. b Proteinuria levels according to the cumulative dose. c, d The probability of achieving clinical outcomes according to the duration of CYC treatment and the cumulative dose, respectively. This probability is significant when the CI does not include the value 1 (the interval is to the right of the dashed vertical line). p50 indicates that the patient has received a CYC dose above (p > 50) and equal/below the median (p ≤ 50), depending on whether the patient belongs to a group with treatment >3 months or ≤3 months. LD, long duration of treatment with CYC (>3 months); SD, short duration of treatment with CYC (≤3 months); CD-CYC, cumulative dose of CYC.
Table 2.
Clinical response 1 year after treatment initiation according to treatment duration and dose of CYC
| Clinical response | Duration of CYC treatment | p value | Effect size | ||
|---|---|---|---|---|---|
| SD | LD | RoR (95% CI) | RR (95% CI) | ||
| Partial remission (PR) | 11/22 (50) | 11/30 (37) | 0.336 | −13 (−40 to +14) | 0.7 (0.4 to 1.4) |
| Complete remission (CR) | 5/22 (23) | 14/30 (47) | 0.077 | +24 (−1 to +49) | 2.1 (0.9 to 4.9) |
| Overall remission (PR + CR) | 16/22 (73) | 25/30 (83) | 0.355 | +10 (−12 to +34) | 1.2 (0.9 to 1.6) |
| Stable eGFR (≥90% of baseline value) | 17/21 (81) | 23/27 (85) | 0.715 | 4 (−17 to +26) | 1.1 (0.8 to 1.4) |
| Clinical response | CD-CYC | p value | Effect size | ||
|---|---|---|---|---|---|
| ≤p50 | >p50 | RoR (95% CI) | RR (95% CI) | ||
| Partial remission (PR) | 11/21 (52) | 9/28 (32) | 0.154 | −20 (−48 to +7) | 0.6 (0.3–1.1) |
| Complete remission (CR) | 4/21 (19) | 15/28 (54) | 0.019 | +35 (+10 to +59) | 2.8 (1.1–7.3) |
| Overall remission (PR + CR) | 15/21 (71) | 24/28 (86) | 0.291 | +14 (−9 to +38) | 1.2 (0.9–1.6) |
| Stable eGFR (≥90% of baseline value) | 18/20 (90) | 21/26 (81) | 0.446 | −9 (−29 to +11) | 0.9 (0.7–1.1) |
CD-CYC, cumulative dose of cyclophosphamide; CYC, cyclophosphamide; LD, long duration (>3 months); p50, the patient has received a CYC dose above or below the median, depending on whether the patient belongs to a group with treatment >3 months or ≤3 months; RoR, reduction of risk expressed as percentage; RR, risk ratio or relative risk; SD, short duration (≤3 months).
Clinical Markers and Outcomes Based on Cumulative Dose of Treatment with CYC
Due to its efficacy and low toxicity, the Euro-Lupus regimen (CYC with a maximum cumulative dose of 3 g) prescribed in patients with lupus nephritis [9] is increasingly being applied in real-world clinical practice to other glomerular diseases such as pMN and ANCA vasculitis. For this reason, we explored whether doses up to this threshold could have a clinically meaningful impact.
Baseline proteinuria levels decreased significantly from the third month onward and throughout the follow-up period in both patient groups (CYC >3 g vs. ≤3 g). Proteinuria levels at 1 year after treatment initiation were lower in patients who received >3 g of CYC, although this difference did not reach statistical significance (0.4 g vs. 1.2 g, p = 0.058) (online suppl. Table S4; Fig. 1b). Similar findings were observed for the magnitude of proteinuria reduction (90% vs. 76%, p = 0.086). No significant differences were found in the final values of serum creatinine, GFR, or serum albumin between groups (online suppl. Table S4). Likewise, no significant differences were observed in the GFR slope at 12 months of follow-up when comparing patients who received a CD-CYC >3 g versus ≤3 g (+0.3 mL/min/1.73 m2 vs. +0.1 mL/min/1.73 m2, p = 0.69) (online suppl. Table S2). A higher percentage of patients who received >3 g of CYC achieved overall remission, although the difference did not reach statistical significance (86% vs. 71%, p = 0.29). However, the proportion of patients who achieved CR was significantly higher in this group (54% vs. 19%, p = 0.02), corresponding to nearly a threefold increase in the probability of achieving CR (RR: 2.8 [95% CI: 1.1–7.3]) (Table 2; Fig. 1d). Notably, after adjusting for baseline proteinuria, kidney function, and cumulative GC dose, a cumulative CYC dose >3 g remained significantly associated with a higher probability of overall remission (OR: 1.2, 95% CI: 1.01–1.4, p = 0.043) and CR (OR: 1.1, 95% CI: 1.001–1.2, p = 0.047) (online suppl. Table S5). Once again, the inclusion of additional potentially confounding variables into the statistical modeling did not yield any statistically significant findings nor did it alter the results shown in online supplementary Table S5.
Adverse Events
During follow-up, ten SAEs were documented (18.5%), with a higher frequency observed in individuals in the LD group (19% vs. 17%) and higher cumulative doses of CYC (9% vs. 0%). However, the relatively small number of patients included and events observed precludes making robust statistical inferences from these results. Notably, two fatal cases occurred in the groups receiving shorter duration and lower cumulative doses of CYC (Table 3). One patient died due to stroke and respiratory arrest, while the other died from lung cancer.
Table 3.
SAEs in a cohort of MN nephrotic patients treated with CYC
| SAEs | Possible relationship | Total | Duration of CYC | CD-CYC | ||
|---|---|---|---|---|---|---|
| SD | LD | ≤p50 | >p50 | |||
| Vascular, n (%) | ||||||
| Emboli | Nephrotic syndrome | 1 (2) | 0 (0) | 1 (25) | 0 (0) | 1 (25) |
| Pulmonary embolism | Nephrotic syndrome | 2 (4) | 2 (50) | 0 (0) | 1 (25) | 1 (25) |
| Renal vein thrombosis | Nephrotic syndrome | 1 (2) | 0 (0) | 1 (25) | 0 (0) | 1 (25) |
| | Total vascular events, n (%) | 4 (7) | 2 (50) | 2 (50) | 1 (25) | 3 (75) |
| Malignancies, n (%) | ||||||
| Lung cancer | Immunosuppression | 1 (2) | 1 (33) | 0 (0) | 1 (33) | 0 (0) |
| Prostate cancer | Membranous nephropathy | 1 (2) | 0 (0) | 1 (33) | 0 (0) | 1 (33) |
| Renal cell carcinoma | Immunosuppression | 1 (2) | 1 (33) | 0 (0) | 0 (0) | 1 (33) |
| | Total malignancies, n (%) | 3 (6) | 2 (67) | 1 (33) | 1 (3) | 2 (67) |
| Infections, n (%) | ||||||
| Epididymitis | Immunosuppression | 1 (2) | 0 (0) | 1 (50) | 0 (0) | 1 (50) |
| Pneumonia | Immunosuppression | 1 (2) | 0 (0) | 1 (50) | 0 (0) | 1 (50) |
| | Total infections, n (%) | 2 (4) | 0 (0) | 2 (100) | 0 (0) | 2 (100) |
| Others, n (%) | ||||||
| Hemorrhagic cystitis | Immunosuppression | 1 (2) | 0 (0) | 1 (100) | 1 (100) | 0 (0) |
| | Total others, n (%) | 1 (2) | 0 (0) | 1 (100) | 1 (100) | 0 (0) |
| | Total of SAEs, n (%) | 10 (19) | 4 (17) | 6 (19) | 3 (14) | 7 (24) |
| | Deaths1, n (%) | 2 (4) | 2 (9) | 0 (0) | 2 (9) | 0 (0) |
Due to the relatively small number of patients and adverse events, we show only the descriptive statistics.
CD-CYC, cumulative dose of CYC; LD, long duration (>3 months); SD, short duration (≤3 months).
1One death occurred before 3 months, due to stroke and respiratory arrest, and another death occurred at 24 months from lung cancer.
Discussion
This study compared LD and SD oral CYC in patients with pMN and did not demonstrate a clear superiority of one regimen over the other. Although no significant differences were observed between the groups in terms of overall renal response (CR+PR) or PR alone, there was a trend toward a higher rate of CR and better proteinuria control in the LD group, as well as a significantly higher rate of CR among patients receiving a cumulative CYC dose exceeding 3 g. Importantly, patients in the SD group exhibited greater tubule-interstitial injury compared to those in the LD group. This likely accounts for the lower baseline eGFR observed in the SD group. The presence of more chronic damage may also have reduced the likelihood of achieving CR in the SD group, particularly given the stringent proteinuria threshold required for this outcome. Possible explanations for these differences include a delay in diagnosis and treatment and, importantly, the caution of the treating nephrologist in administering higher doses of CYC for longer periods in patients with tubulointerstitial damage or a history of cancer. Beyond these findings, the clinical remission rates observed in both groups of patients in this cohort are consistent with those reported in pioneering clinical trials comparing chlorambucil or CYC with supportive care [3–5, 10], as well as in more recent clinical trials comparing CYC with other immunosuppressants, including rituximab and calcineurin inhibitors [11–14].
Our study results are concordant with a recent randomized clinical trial involving 114 Indian patients (6). In that study, a regimen with low dose of GC (prednisolone 0.5 mg/kg/day in months 1, 3, and 5) and oral CYC (1–1.5 mg/kg/day in months 2, 4, and 6) was not inferior to an standard-dose regimen with GC and CYC, including intravenous methylprednisolone, for achieving CR or PR of proteinuria between months 6 and 24 (78.94% vs. 87.71%, respectively, for intention-to-treat analysis).
As most patients in this study were treated before serological markers (e.g., anti-PLA2R) became routinely available, it is not possible to assess immunologic responses to LD and SD-CYC and their association with key clinical markers such as proteinuria and kidney function. Despite the lower baseline eGFR in the SD group, the slope of eGFR decline was comparable between the groups, supporting the finding that LD-CYC is not superior to SD-CYC. These results are in line with the emerging trend toward shorter intravenous CYC-based regimens with lower cumulative doses [15–17]. A retrospective cohort study of 55 Uruguayan nephrotic patients with pMN treated between 1990 and 2017 with a 6-month course of alternating GC (months 1, 3, and 5) and intravenous CYC regimen (single dose of 15 mg/kg on the first day of months 2, 4, and 6) showed that 71% of patients achieved overall remission (CR 42%, PR 29%) at 24 months, 29% nonresponse, and 27% relapsed at 34 months posttreatment discontinuation [15]. Another small cohort study reported that 17 pMN patients (9 newly diagnosed, 8 relapses) with severe NS achieved PR within 6 months of treatment with monthly intravenous CYC and oral GC, accompanied by a reduction in anti-PLA2R antibodies and an improvement in eGFR, with a CD-CYC and GC of approximately half the standard regimen [17]. Nonetheless, larger studies with longer follow-up periods are needed to draw more definitive conclusions regarding the trajectory of kidney function and the risk of relapse.
Tolerance and toxicity associated with CYC remain persistent concerns for both patients and treating nephrologists. Consequently, safer therapeutic alternatives or combinations of immunosuppressive agents at lower doses have been explored. A retrospective cohort study of 100 European Caucasian patients with nephrotic pMN demonstrated that the risk of both SAE and non-SAEs was significantly lower with rituximab compared to CYC, even after adjusting for baseline characteristics, while clinical remission rates were comparable between the two treatments [18]. In a separate cohort of 272 Dutch patients with pMN followed over 5 years, the adjusted risk of malignancy was found to be 3.2 times higher among those treated with CYC [19]. The effectiveness and safety of low-dose CYC also have been evaluated in Asian patients [20, 21]. Notably, in a cohort of 90 Japanese patients with MN treated with CYC for 6 months (50 mg/day for the first 3 months, followed by 25 mg/day for the subsequent 3 months) in combination with GC and followed for a median of 8.5 years, there were 14 deaths, and 8 cases of malignancy were reported during the observation period. In our study, only one case of cancer-related death occurred in a patient who received SD-CYC treatment; however, the short follow-up period does not allow for definitive conclusions to be drawn. In the recent Indian study [6], more non-SAEs were observed in the standard-dose group compared to low-dose group, while SAEs were reported in 4 patients (including 2 deaths due to severe infection) and 2 patients (including one sudden death of probable cardiac cause), respectively. These concerns have prompted the adoption of more restrictive therapeutic strategies such as stricter criteria for administering immunosuppressive therapy [22], and the evaluation of rituximab in combination with low-dose CYC. This approach has shown favorable safety profile, good tolerability, and high rates of clinical remission [23]. Thus, rituximab-based regimens are currently the first choice for most nephrotic patients with pMN, and CYC-based regimens are reserved for very high-risk cases or for refractory patients. Furthermore, novel options such as obinutuzumab or plasma-cell-targeted agents are emerging therapies that require formal validation, but could potentially transform future clinical practice. In any case, CYC should be used only after careful patient selection.
There are several limitations to the current study, including its retrospective design, small sample size, lack of available anti-PLA2R measurements, differences in patient ethnicity and comorbidities between the comparator groups, and relatively short follow-up period. Although the ethnic and geographic heterogeneity of our study enhances the generalizability of our findings, it may also introduce variability in the real-world clinical practice. For all these reasons, our results should be interpreted cautiously. Nonetheless, the use of a similar clinical approach and periodic follow-up across participating centers are notable strengths of this cohort. Moreover, the findings from this study open avenues for further prospective research to determine the optimal CYC dosing in patients with pMN at moderate to high risk of progression, and to explore the mechanistic role of anti-PLA2R and the immunological response to this therapy.
Conclusion
This study compared SD (≤3 months) and LD (>3 months) oral CYC with GC for the treatment of pMN and found no clear advantage for either regimen. Although there was a trend toward more CRs and better proteinuria control in the LD group, these patients tended to have better eGFR and less chronic histologic damage at the start of treatment compared to the SD group. Adverse events were also slightly more frequent with LD-CYC. In summary, we found no statistically significant differences between the SD-CYC and LD-CYC regimens; however, these findings require confirmation in adequately powered prospective trials with longer follow-up.
Statement of Ethics
This study protocol was reviewed and approved by Ohio State Biomedical Sciences IRB at The Ohio State University (OSU IRB Approval No. 2020H0046, date of decision: February 4, 2020), by Allegheny Health Network IRB at AHN Research Institute in Pittsburgh (date of decision: December 20, 2019) and by Zydus Hospital Ethics Committee (IRB), in India (date of decision: March 7, 2020). This study was performed in accordance with the Declaration of Helsinki. This human study was approved by Ohio State Biomedical Sciences Institutional Review Board (IRB). The need for written informed consent was waived by the Ohio State Biomedical Sciences IRB and HIPAA Research Authorization, Approval: OSU IRB No. 2020H0046, Date of the decision: 2/4/2020. This waiver was made due to the retrospective and anonymous nature of the data used.
Conflict of Interest Statement
S.A., J.E.R.-R., M.C., H.P., R.P., H.B., L.M., and O.O. have no conflict of interest to disclose. B.R. reports grants from Biogen, NIK, and Lupus Research Association; consulting fees from Alexion, Novartis, Vera, Alpine, Calliditas, Otsuka, Travere, Biogen, Incyte, Century, and Atriva; and lecture honorary from Medscape and Advocacy Group (unpaid) at the International Society of Glomerular Diseases and Lupus Foundation of America. I.A. is site principal investigator on ITN REBOOT Membranous Nephropathy Study (NCT03949855) and site principal investigator on phase 1b/2a M-PLACE study (NCT04145440).
Funding Sources
No specific financial support was obtained for the preparation of this article.
Author Contributions
Swati Arora, MD: conceptualization, data curation, investigation, methodology, validation, visualization, and writing – original draft, review, and editing. Jorge E. Rojas-Rivera, MD, MSc: formal analysis, data curation, investigation, methodology, software, validation, visualization, and writing – original draft, review, and editing. Isabelle Ayoub, MD: conceptualization, data curation, investigation, methodology, project administration, supervision, validation, visualization, and writing – original draft, review, and editing. Brad H. Rovin, MD: supervision and writing – original draft, review, and editing. Madeleine Chung, MD; Himanshu Patel, MD; Rajshree Patil, MD; Hitesh Bhatia, MD; Luba R. Muaddi, MD; and Omar Osman, MD: data curation and review of the final version of the publication. All authors critically reviewed the manuscript and approved the final version for publication.
Funding Statement
No specific financial support was obtained for the preparation of this article.
Data Availability Statement
The data supporting the findings of this study are not publicly available due to privacy reasons, but are available from the corresponding author upon request, with the coordination and permission of all coauthors.
Supplementary Material.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The data supporting the findings of this study are not publicly available due to privacy reasons, but are available from the corresponding author upon request, with the coordination and permission of all coauthors.