Hemodialysis and imatinib: Plasma levels, efficacy and tolerability in a patient with metastatic GIST - Case report

Purpose: To study plasma levels, efficacy and tolerability of imatinib in a patient affected by metastatic GIST treated with oral Imatinib and undergoing hemodialysis. Patients and methods: The patient suffered from metastatic GIST to the liver having a mutation of exon 9 of KIT. He was on hemodialysis and received first-line treatment with imatinib 400 mg/day. Results: The overall mean plasma level of imatinib was 1875,4 ng/ml pre-dialysis, 1553,0 ng/ml post-dialysis and 1998,1 ng/ml post-24h. In red blood cells the overall mean level of imatinib was 619,5 ng/ml pre-dialysis, 484,9 ng/ml post-dialysis and 663,1 ng/ml post-24h. The plasma level of nor-imatinib/imatinib was 16,2% pre-dialysis, 15,6% post-dialysis and 16,4% post-24h. Comparing our findings regarding levels of imatinib in plasma and RBC, we found a statistically significant difference between pre-dialysis and post-dialysis (respectively p < 0,001 and p = 0,002), post-dialysis and post-24h (both p < 0,001), pre-dialysis and post-24h (respectively p = 0.035 and p = 0,042). Ultimately, regarding nor-imatinib/imatinib in plasma, we did not find any statistically significant difference between pre-dialysis and post-dialysis (p = 0,091), post-dialysis and post-24h (p = 0,091), pre-dialysis and post-24h (p = 0.903). Currently the patient is receiving oral imatinib 400 mg/day with radiological evidence of response. Conclusion: In this case, hemodialysis did not affect significantly imatinib plasma levels. The statistically significant difference between pre- and post-dialysis can be explained by the fact that dialysis may likely contribute to a small portion of the normal metabolism of imatinib. The evaluation of imatinib levels in RBC and of its main metabolite in plasma also suggests that hemodialysis did not affect other aspects of the elimination of the drug.