The predictive value of cystatin C in monitoring of B non-hodgkin lymphomas: relation to biochemical and clinical parameters

Incorporating Cystatin C to Predict Methotrexate Elimination in Patients with CNS Lymphoma and Suspicious Renal Function

High-dose methotrexate (MTX; ≥1 g/m²) is a renally eliminated and nephrotoxic first-line therapy for central nervous system (CNS) lymphoma. Creatinine-based estimation of renal function is the recommended approach to dosing MTX in these cases, but nonrenal determinants of creatinine production and elimination in cancer patients such as malnutrition and cachexia lead to overestimation of glomerular filtration rate (GFR) by this method and a heightened risk for drug toxicity. Serum cystatin C is one of the first readily available, relatively inexpensive, endogenous biomarkers to emerge as a practical adjunct to creatinine for estimation of renal function for drug dosing. In this report, we describe two cases where cystatin C was used in conjunction with creatinine to inform MTX dosing for CNS lymphoma. In both cases, the estimated GFR was nearly 40% lower with the combination of the two biomarkers compared to creatinine-only estimates. Empiric MTX dose reductions as a product of these results likely spared the patients sustained exposure to toxic drug concentrations and facilitated earlier administration of supportive care interventions. Further prospective investigations with validated dosing regimens including cystatin C are warranted for high-dose MTX.

Biochemical and Clinical Impact of Organic Uremic Retention Solutes: A Comprehensive Update

In this narrative review, the biological/biochemical impact (toxicity) of a large array of known individual uremic retention solutes and groups of solutes is summarized. We classified these compounds along their physico-chemical characteristics as small water-soluble compounds or groups, protein bound compounds and middle molecules. All but one solute (glomerulopressin) affected at least one mechanism with the potential to contribute to the uremic syndrome. In general, several mechanisms were influenced for each individual solute or group of solutes, with some impacting up to 7 different biological systems of the 11 considered. The inflammatory, cardio-vascular and fibrogenic systems were those most frequently affected and they are one by one major actors in the high morbidity and mortality of CKD but also the mechanisms that have most frequently been studied. A scoring system was built with the intention to classify the reviewed compounds according to the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence. Among the highest globally scoring solutes were 3 small water-soluble compounds [asymmetric dimethylarginine (ADMA); trimethylamine-N-oxide (TMAO); uric acid], 6 protein bound compounds or groups of protein bound compounds [advanced glycation end products (AGEs); p-cresyl sulfate; indoxyl sulfate; indole acetic acid; the kynurenines; phenyl acetic acid;] and 3 middle molecules [β₂-microglobulin; ghrelin; parathyroid hormone). In general, more experimental data were provided for the protein bound molecules but for almost half of them clinical evidence was missing in spite of robust experimental data. The picture emanating is one of a complex disorder, where multiple factors contribute to a multisystem complication profile, so that it seems of not much use to pursue a decrease of concentration of a single compound.

Dexamethasone Modifies Cystatin C-Based Diagnosis of Acute Kidney Injury During Cisplatin-Based Chemotherapy

BACKGROUND/AIMS

Plasma cystatin C (pCysC) may be superior to serum creatinine (sCr) as a surrogate of GFR. However, the performance of pCysC for diagnosing acute kidney injury (AKI) after cisplatin-based chemotherapy is potentially affected by accompanying corticosteroid anti-emetic therapy and hydration.

METHODS

In a prospective observational study pCysC, sCr, urinary kidney injury molecule-1 (KIM-1), and urinary clusterin were measured over 2 weeks in 27 patients given first-cycle chemotherapy. The same variables were measured over 2 weeks in Sprague-Dawley rats given a single intraperitoneal injection of dexamethasone, cisplatin, or both, and in controls.

RESULTS

In patients, pCysC increases were greater than sCr 41% vs. 16%, mean paired difference 25% (95% CI: 16-34%)], relative increases were ≥ 50% in 9 patients (35%) for pCysC compared with 2 (8%) for sCr (p = 0.04) and increases in sCr were accompanied by increased KIM-1 and clusterin excretion, but increases in pCysC alone were not. In rats, dexamethasone administration produced dose-dependent increases in pCysC (and augmented cisplatin-induced increases in pCysC), but did not augment histological injury, increases in sCr, or KIM-1 and clusterin excretion.

CONCLUSIONS

In the presence of dexamethasone, elevation of pCysC does not reliably diagnose AKI after cisplatin-based chemotherapy.

Serum Cystatin C as a Biomarker in Diffuse Large B-Cell Lymphoma

Elevated serum levels of cystatin C are found to be related to poor outcome and metastatic potential of some malignant disorders. To evaluate the clinical prominence of serum cystatin C in diffuse large B-cell lymphoma (DLBCL), blood samples were obtained from 58 patients at the time of diagnosis and paired blood samples were obtained from 22 patients at the time of remission. Also, serum cystatin C level was measured in matched healthy controls. Serum cystatin C levels were significantly more elevated in DLBCL patients than in controls (p < 0.0001). Furthermore, paired-sample analysis revealed that pretreatment cystatin C levels were reduced significantly in patients who achieved remission after therapy (p = 0.016). High serum cystatin C levels were correlated with age over 60 years (p = 0.049), extra-nodal involvement (p = 0.005) and with high serum lactate dehydrogenase (LDH) (p < 0.013). Elevated serum cystatin C levels were associated with extra-nodal involvement and they were significantly reduced to normal range after the remission. However, Kaplan-Meier curves revealed no survival difference in the pretreatment serum cystatin C levels. Therefore, serum cystatin C may be a novel biomarker that reflects tumor burden in DLBCL but bears no prognostic significance regarding survival.