Pharmacokinetic evaluation of platinum derived from cisplatin administered alone and with pemetrexed in head and neck cancer patients.

PURPOSE: This phase I study characterized the pharmacokinetics of free and total platinum derived from cisplatin administered alone and in combination with pemetrexed. Secondary objectives were to assess the pharmacokinetics of pemetrexed when it is combined with cisplatin as well as to evaluate the safety profile and document antitumor activity associated with this combination.

METHODS: An open-label, two-arm, cross-over phase 1 study was performed in patients with squamous cell carcinoma of the head and neck, age > or =18 years, an Eastern Cooperative Oncology Group performance status of 0-2, and adequate organ function. Blood samples were taken and pharmacokinetics evaluated for the first two cycles using noncompartmental analysis. Patients received either pemetrexed (500 mg m(-2)) plus cisplatin (75 mg m(-2)) administered in cycle 1 followed by cisplatin alone in cycle 2; or in the reverse order (i.e., cisplatin alone in cycle 1 followed by pemetrexed plus cisplatin in cycle 2). Each treatment cycle was 21 days and patients received folic acid, vitamin B(12) supplementation, and dexamethasone prophylaxis. After the first two cycles, patients continued study treatment with pemetrexed plus cisplatin every 3 weeks up to a maximum of six total treatment cycles. Toxicities were graded by the investigators according to the National Cancer Institute Common Toxicity Criteria for Adverse Events (CTCAE), version 3.0.

RESULTS: A total of 13 patients were treated; one patient was discontinued from the study after cycle 1 for failure to meet baseline eligibility criteria for renal function. The ratios and 90% confidence intervals (CI) comparing the pharmacokinetics for cisplatin administered with pemetrexed to those for cisplatin administered alone for free platinum were: C(max) = 1.08 (CI: 0.92, 1.27) and AUC = 0.93 (CI: 0.82, 1.06); and, total platinum were: C(max) = 0.97 (CI: 0.88, 1.06) and AUC = 0.87 (CI: 0.81, 0.93). These results indicate that platinum pharmacokinetics (free and total) are similar, whether cisplatin is administered alone or combined with pemetrexed. The pemetrexed pharmacokinetic results were consistent with those from previous single-agent pemetrexed studies and a previous study of pemetrexed in combination with cisplatin. The combination of pemetrexed and cisplatin did not show any unexpected toxicities. Consistent with the platinum pharmacokinetic results, co-administration with pemetrexed did not appear to enhance cisplatin-related toxicities. Of the 13 treated patients, 11 had stable disease as the best overall response and 2 had progressive disease.

CONCLUSIONS: The pharmacokinetics of free platinum derived from cisplatin were not altered by co-administration with pemetrexed, and in agreement with this, no unexpected cisplatin-induced toxicities were observed when these drugs were combined.