Rasburicase Effectively Lowers Serum Uric Acid Levels in High Risk, Poor Performance Status Patients with Hematologic Malignancies

Tumor lysis remains a significant cause of morbidity and mortality in patients with highly proliferative hematologic malignancies. Traditionally, intravenous hydration and oral allopurinol have been the mainstays of therapy. However in some patients, hyperuricemia and renal failure still occur. The resultant renal failure precludes the administration of full doses of chemotherapy and results in a poor treatment outcome. Recently we participated in a large phase III randomized trial comparing rasburicase with standard allopurinol therapy. Rasburicase is a recombinant urate oxidase that effectively reduces serum uric acid due to conversion of uric acid into allantoin, a readily excretable and soluble substance. The results of that study are reported in a separate abstract. However while the study was open, we treated 12 extremely high risk, newly diagnosed hematologic malignancy patients who were ineligible for the study with commercially available rasburicase off study. The reasons for study ineligibility were ECOG Performance Status 4 and/or expected survival of less than one month. Other baseline characteristics: Diagnosis: Burkitts ALL: 3, AML: 7, CML-BP: 1, T-ALL: 1; Age: 64 (27–85), Sex: 6M/6F; WBC: 58,000/mm³ (1.6- 245,000); LDH: 2201 U/l (1068- >2500); # of preexisting comorbid medical conditions: 4 (0–7); chemotherapy: hyper-CVAD: 4, standard ara-c based rx: 5, high dose ara-C based rx: 3. Nine patients received one dose of rasburicase (0.2 mg/kg IV), 3 patients required a second dose. The median uric acid levels were: pretreatment : 9.2 mg/dl (2.8–28.6), at 24 hours: <0.2 (0.2–7.5) and at 48 hours: <0.2 (<0.2–4.9). All patients achieved normal serum uric acid level by day 2. The median baseline creatinine was 2.6 mg/dl (0.7 – 5.6); by day seven 10 patients had a serum creatinine less than 2 mg/dl (day 7 median creatinine 0.9, range 0.4–5.5). Four patients achieved CR to chemotherapy, 5 had refractory disease and 3 had induction death. Administration of rasburicase in this extremely high risk group of patients resulted in a rapid decrease in serum uric acid levels. In many patients this allowed for preservation of or improvement in renal function and administration of chemotherapy. Although some patients had a poor outcome due to the aggressive nature of their underlying disease, 4 of 12 patients (33%) attained CR and were able to receive subsequent cycles of intensive chemotherapy without incident.