Two identical multicenter, randomized, double-blind, double-dummy studies of zoledronic acid 4 mg given as a 5-minute intravenous infusion or pamidronate 90 mg given as a 2-hour intravenous infusion were conducted in 185 patients with hypercalcemia of malignancy (HCM). NOTE: Administration of zoledronic acid 4 mg given as a 5-minute intravenous infusion has been shown to result in an increased risk of renal toxicity, as measured by increases in serum creatinine, which can progress to renal failure. The incidence of renal toxicity and renal failure has been shown to be reduced when zoledronic acid 4 mg is given as a 15-minute intravenous infusion. Zoledronic acid should be administered by intravenous infusion over no less than 15 minutes [see Warnings and Precautions (5.1, 5.2), Dosage and Administration (2.4)]. The treatment groups in the clinical studies were generally well balanced with regards to age, sex, race, and tumor types. The mean age of the study population was 59 years; 81% were Caucasian, 15% were Black, and 4% were of other races. Sixty percent (60%) of the patients were male. The most common tumor types were lung, breast, head and neck, and renal.
In these studies, HCM was defined as a corrected serum calcium (CSC) concentration of greater than or equal to 12.0 mg/dL (3.00 mmol/L). The primary efficacy variable was the proportion of patients having a complete response, defined as the lowering of the CSC to less than or equal to 10.8 mg/dL (2.70 mmol/L) within 10 days after drug infusion.
To assess the effects of zoledronic acid versus those of pamidronate, the two multi-center HCM studies were combined in a preplanned analysis. The results of the primary analysis revealed that the proportion of patients that had normalization of corrected serum calcium by Day 10 were 88% and 70% for zoledronic acid 4 mg and pamidronate 90 mg, respectively (P = 0.002) (see Figure 1). In these studies, no additional benefit was seen for zoledronic acid 8 mg over zoledronic acid 4 mg; however, the risk of renal toxicity of zoledronic acid 8 mg was significantly greater than that seen with zoledronic acid 4 mg.
Secondary efficacy variables from the pooled HCM studies included the proportion of patients who had normalization of corrected serum calcium (CSC) by Day 4; the proportion of patients who had normalization of CSC by Day 7; time to relapse of HCM; and duration of complete response. Time to relapse of HCM was defined as the duration (in days) of normalization of serum calcium from study drug infusion until the last CSC value less than 11.6 mg/dL (less than 2.90 mmol/L). Patients who did not have a complete response were assigned a time to relapse of 0 days. Duration of complete response was defined as the duration (in days) from the occurrence of a complete response until the last CSC less than or equal to 10.8 mg/dL (2.70 mmol/L). The results of these secondary analyses for zoledronic acid 4 mg and pamidronate 90 mg are shown in Table 10.
Table 11 describes an overview of the efficacy population in three randomized zoledronic acid trials in patients with multiple myeloma and bone metastases of solid tumors. These trials included a pamidronate-controlled study in breast cancer and multiple myeloma, a placebo-controlled study in prostate cancer, and a placebo-controlled study in other solid tumors. The prostate cancer study required documentation of previous bone metastases and 3 consecutive rising PSAs while on hormonal therapy. The other placebo-controlled solid tumor study included patients with bone metastases from malignancies other than breast cancer and prostate cancer, including NSCLC, renal cell cancer, small cell lung cancer, colorectal cancer, bladder cancer, GI/genitourinary cancer, head and neck cancer, and others. These trials were comprised of a core phase and an extension phase. In the solid tumor, breast cancer and multiple myeloma trials, only the core phase was evaluated for efficacy as a high percentage of patients did not choose to participate in the extension phase. In the prostate cancer trials, both the core and extension phases were evaluated for efficacy showing the zoledronic acid effect during the first 15 months was maintained without decrement or improvement for another 9 months. The design of these clinical trials does not permit assessment of whether more than one-year administration of zoledronic acid is beneficial. The optimal duration of zoledronic acid administration is not known.
The studies were amended twice because of renal toxicity. The zoledronic acid infusion duration was increased from 5 minutes to 15 minutes. After all patients had been accrued, but while dosing and follow-up continued, patients in the 8 mg zoledronic acid treatment arm were switched to 4 mg due to toxicity. Patients who were randomized to the zoledronic acid 8 mg group are not included in these analyses.
Each study evaluated skeletal-related events (SREs), defined as any of the following: pathologic fracture, radiation therapy to bone, surgery to bone, or spinal cord compression. Change in antineoplastic therapy due to increased pain was a SRE in the prostate cancer study only. Planned analyses included the proportion of patients with a SRE during the study and time to the first SRE. Results for the two zoledronic acid placebo-controlled studies are given in Table 12.
In the breast cancer and myeloma trial, efficacy was determined by a noninferiority analysis comparing zoledronic acid to pamidronate 90 mg for the proportion of patients with a SRE. This analysis required an estimation of pamidronate efficacy. Historical data from 1,128 patients in three pamidronate placebo-controlled trials demonstrated that pamidronate decreased the proportion of patients with a SRE by 13.1% (95% CI=7.3%, 18.9%). Results of the comparison of treatment with zoledronic acid compared to pamidronate are given in Table 13.
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