Concurrent administration of sodium thiosulfate (STS) can protect against the nephrotoxic effects of even very-high-dose cisplatin (CDDP) (i.e., 270 mg/m2 given intraperitoneally). The effect of STS on the pharmacology and toxicity of CDDP was investigated in patients receiving at each treatment 90 mg of CDDP/m2 intraperitoneally, with STS given concurrently on alternate cycles by the intravenous route. The patients received a total of 38 courses of therapy, 21 without STS and 17 with STS. STS reduced the total exposure to diethyldithiocarbamate-reactive CDDP for the peritoneal cavity and plasma by 36% and 25%, respectively. When given alone, CDDP caused a statistically significant acute reduction in creatinine clearance levels; this reduction was less evident when STS was given. We conclude that, whereas STS does reduce systemic exposure, the magnitude of this effect was not sufficient to account for the ability of STS to protect against high-dose CDDP.

Dipyridamole increases the toxicity of methotrexate in a concentration-dependent manner. We hypothesized that concurrent intraperitoneal administration of both drugs would result in high peritoneal concentrations with much lower plasma concentrations, permitting a selective increase in the activity of methotrexate against intraperitoneal tumors without enhancing systemic toxicity. Initially, 2.16 mg/m2/d methotrexate and 12 mg/m2/d dipyridamole were delivered together as a constant intraperitoneal infusion for 48 hours. With escalation of chemotherapy, eventually 4.32 mg/m2/d methotrexate was administered for 168 hours. Forty-seven courses were administered to 18 patients. The mean peritoneal to plasma concentration ratios of methotrexate and non-protein bound dipyridamole were 71.6 +/- 34.8 and over 2,300, respectively. Chemical peritonitis was the dose-limiting toxicity. Three patients had some evidence of a response (two with decreasing tumor markers, and the third with a reduction in ascites). We conclude that the drug concentrations are in an appropriate range for selective intraperitoneal biochemical modulation of methotrexate, and that it is feasible to expose tumors confined to the peritoneal cavity to these drugs for long periods of time.

Thioguanine (TG) is an antimetabolite with established antileukemic activity. The most pharmacologically rational manner of TG administration is continuous infusion. Intraperitoneal (IP) delivery of TG provides the opportunity to definitively test the concept of high-dose, long-term antimetabolite administration. The high systemic clearance and in vitro activity of TG against ovarian carcinoma suggested that it would be an excellent candidate for IP administration as a prolonged infusion. TG was administered as a 48-hour continuous IP infusion in this phase I/pharmacokinetic study. TG infusions were administered using a portable, programmable pump (Pancretec Provider Model 2000; Pancretec, Inc, San Diego). Twenty-five patients were treated. At a dose of 900 mg/m2/48 h, TG produced unacceptably severe myelosuppression. The dose-limiting toxicity was granulo-cytopenia. Other toxicities were mild: emesis, alopecia, skin rashes, and photosensitivity reactions. IP TG did not produce chemical peritonitis, hepatotoxicity, or mucositis. The pharmacokinetics of IP TG were determined in 16 patients. TG levels were measured by reverse-phase high-performance liquid chromatography (HPLC). At steady state, the mean peritoneal to plasma TG ratio was 1,800 at the maximum tolerated dose (MTD). Steady-state TG levels in the peritoneal cavity and plasma were 2 mmol/L and 1.1 mumol/L, respectively, at a dose of 744 mg/m2. The elimination half-life of TG from the peritoneal cavity was one hour. TG exhibited linear pharmacokinetics over the dosage range investigated. Encouraging clinical activity was seen with IP TG. There was one partial response (PR) and four minor responses (MR). TG can be safely administered by the IP route. The recommended dose for phase II testing is 744 mg/m2/48 h. IP TG has a favorable pharmacokinetic advantage and has demonstrated encouraging clinical activity. Further studies of IP TG infusions are warranted.

Ninety-eight evaluable patients with nonresectable regional or metastatic non-small cell bronchogenic carcinoma were treated with a four-drug combination chemotherapy program of methotrexate, cyclophosphamide, hexamethylmelamine, and CCNU (MCHC). Fifteen partial or complete responses (15%) were obtained, all but one of which occurred in good performance status (0-1) patients. While "responders lived longer than non-responders", this was due more to initial performance status among responding patients than to achievement of partial (greater than 50%) or complete disease regression. Evaluation of those patients with good performance status (PS 0-1), indicated no statistically significant differences in median survival time for complete response and partial response patients compared to patients with "improved" or "stable" disease status in this group. This combination of modestly active single agents produced disappointing results in our lung cancer population. A search for more active single agents in lung cancer is necessary.