TOP 46 - Kidney Functional Reserve Assessment in Adolescent and Young Adult Cancer Survivors: A Cross-Sectional Study Using Cystatin C

Publication Number: 1805.TOP 46

Heepke Knickel, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; Stefanie W. Benoit, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; Brian Turpin, Cincinnati Children's Hospital Medical Center, Cinc, OH, United States

Background: Kidney functional reserve (KFR) reflects the kidneys' increase in glomerular filtration rate (GFR) when exposed to stress. KFR naturally declines with age but can also be lost due to acute or chronic kidney insults which are common among patients with cancer. Assessing KFR may identify subclinical kidney injury in cancer survivors sooner, but a lack of standardized methods has hindered the clinical application of KFR in this group. Cystatin C-derived KFR (CysC-KFR) protocols in healthy young adults and adults with CKD correlate with more complex procedures (e.g. nuclear medicine assay) and may pave the way for broader clinical use(1).

Objective: The objective of this study was to refine KFR assessment methodology in adolescent and young adult (AYA) cancer survivors. Our aims were to measure CysC-KFR in healthy AYAs and compare KFR between healthy AYAs and cancer survivors. We hypothesized that CysC-KFR values in healthy AYAs would be similar to those previously published, and that KFR would be lower in cancer survivors than healthy controls.

Design/Methods: We recruited 2 cohorts of AYA individuals into this cross-sectional study: cancer survivors with normal GFR who received nephrotoxic chemotherapy, and healthy individuals. Study participants ate a low-protein diet the day before the study visit, then drank a 1.5g/kg protein shake. Five hourly measurements of creatinine (Cr) and CysC were obtained, and KFR was calculated as the difference from baseline to maximum eGFR that were estimated using the Full Age Spectrum equation(2). Seven cancer survivors and 12 controls have completed their study visits (Table 1). All available eGFR measurements for cancer survivors were >90ml/min/1.73m2 during treatment and survivorship (Table 2). Mean CysC-KFR was 14.1±5.6 ml/min/1.73m2 in healthy controls, which is comparable to a published CysC-KFR value in healthy AYAs(3). Cr- and CysC-KFR were not statistically different in healthy controls (13.8 vs 14.1ml/min/1.73m2, p=0.9) or in cancer survivors (9.1 vs 13.7ml/min/1.73m2, p=0.5), respectively. CysC-KFR was lower in older versus younger survivors (4.2±5.9 vs 23.2±1.6 ml/min/1.73m2, p=0.12, Figure 1). We plan to complete data analysis in Jan 2026. Additional analyses will examine associations between KFR, age, sex, and cancer treatment-related risk factors (e.g. nephrotoxic chemotherapy exposure).
1. Nephrol Dial Transplant (2022) 37:1118-1124. doi:10.1093/ndt/gfab188
2. Nephrol Dial Transplant (2016) 31:798-806, doi:10.1093/ndt/gfv454
3. Scand J Clin Lab Invest. (2013) 73(4): 265-268. doi:10.3109/00365513.2013.765964.

Table 1. Demographic data of study participants at time of study visit.
IQR = interquartile range. BMI = body mass index. Cr-GFR = estimated glomerular filtration rate based on serum creatinine. CysC-GFR = estimated GFR based on serum cystatin C.

Table 2. Available glomerular filtration rate measurements during and after cancer treatment for cancer survivors.
n=7. Most recent survivorship result documented if multiple results available. GFR in mL/min/1.73m2. NM = nuclear medicine.

Figure 1. Cystatin C kidney functional reserve in healthy controls and cancer survivors stratified by age
(A) cystatin C KFR in the 12 healthy participants stratified by age. There were 2 participants in the '15-20' group, 4 in '21-26', 3 in '27-32', and 3 in '33-39'. (B) Cystatin C KFR in the 4 cancer survivors stratified by age. There were 2 participants in the '15-20' group, and 2 in '32-39'. KFR = kidney functional reserve.