Breast cancer drug raises creatinine without necessarily signaling kidney damage, study finds

A research team from Kanazawa University and Shinshu University has found that a breast cancer drug called abemaciclib can cause a rise in serum creatinine without indicating actual kidney damage. This occurs in many patients who take the medication. The study followed 63 patients, all women except one, and measured creatinine levels over 24 weeks of treatment.

Creatinine increased in 62 of the 63 patients, remaining stable through the treatment period before dropping after treatment interruption. Interestingly, cystatin C, another protein used to assess kidney function, showed a different pattern in 29 patients who had both creatinine and cystatin C tested during treatment. In 28 of these cases, creatinine and cystatin C moved in opposite directions, indicating that cystatin C is less affected by the drug.

The researchers also discovered that, in 15 of the 29 patients (52%), creatinine and cystatin C already disagreed before treatment began. Without a baseline cystatin C measurement, this discrepancy could be misinterpreted as drug-induced kidney damage or a decline in kidney function. The study suggests that measuring cystatin C baseline may help doctors interpret creatinine rises during treatment, allowing patients to continue effective therapy without unnecessary dose reductions or interruptions.

Assistant Professor Hiroaki Watanabe from the Faculty of Pharmacy at Kanazawa University emphasized the importance of this approach, stating that when creatinine rises after starting abemaciclib, it does not necessarily mean the kidneys are failing.