Introduction/Background Poly (ADP-ribose) polymerases inhibitors (PARPi) are integral in the treatment of ovarian cancer. PARPi inhibit creatinine transporters in the nephron which can impact creatinine levels. Creatinine is the most used surrogate marker for kidney injury. Creatinine elevations often lead to dose modifications or treatment cessation. The purpose of this study was to evaluate the use of cystatin C levels as a potential surrogate of kidney function, compared to creatinine, during PARPi therapy.

Methodology A retrospective, single-institutional database was used to identify ovarian cancer patients treated with PARPi that had cystatin C and creatinine levels measured during PARPi therapy. Data collected included drug used, dose interruptions and modification, cystatin c, creatinine, creatinine based estimated glomerular filtration rate (eGFR), and cystatin C based eGFR. Cystatin C-based eGFR was compared to creatinine-based eGFR to assess PARP inhibitors’ effect on renal function.

Results 40 patients treated with PARPi were found to have at least one cystatin C during therapy. 20 patients had more than one cystatin C measured. 45% of patients had increasing creatinine with increasing duration of therapy. Nine (22.5%) patients had PARPi modified or held due to an elevated creatinine, among these individuals, 33.3% patients had a higher cystatin C based eGFR compared to creatinine based eGFR. 25% of the 40 patients were found to have a lowering creatinine based eGFR, while cystatin C based eGFR remained stable. 15% of patients had a cystatin C based eGFR that was lower compared to the corresponding creatine based eGFR.

Conclusion Elevations in creatine leads to significant dose modifications of PARPi. In this limited series, in many cases, the cystatin C levels do follow creatinine levels, suggesting dose reductions may not be needed in all cases. Further assessment of additional markers such as iothalamate clearance may identify an improved surrogate of renal function in patients receiving PARPi.

Disclosures None