[Experimental study on carboplatin toxicity--a comparison with cisplatin]

The toxic potencies of cisplatin and carboplatin were compared in male Wistar rats. The tissue concentration of platinum in rats was 5- to 13-fold larger with cisplatin treated group than carboplatin treated one. The histopathologic examination of various organs revealed severe myelosuppression and mild toxicity in the kidney, testis, spleen and intestine of rats treated with carboplatin. The toxicity of carboplatin was milder than cisplatin in all organs except bone marrow. This reduced toxicity of carboplatin can be accounted for by the presence of a stable dicarboxylate chelate ring structure of this drug, resulting in a much slower rate of hydrolysis to the active form, and the differences in nuclear protein phosphorylation between normal cells and tumor cells. The decreased nephrotoxicity of carboplatin may be due in part to lower drug accumulation in the renal tubular epithelium via the basement transport mechanism.

Evolution of high-dose cisplatin

High-dose cisplatin therapy, defined as 200 mg/m2/course, is currently undergoing extensive clinical trials in a variety of solid tumors. The reduction of the incidence and severity of cisplatin-induced nephrotoxicity has led to clinical trials of higher doses of cisplatin. By maintaining nephrotoxicity to acceptable levels, dose response relationships have shown increased efficacy of cisplatin therapy. However, new dose-limiting toxicities, primarily severe neurotoxicity and myelosuppression, have prevented further dosing increases. The following review will trace the evolution and the current status of high-dose cisplatin therapy. In addition, a summary of the dose-limiting non-renal toxicities and their relationship to pharmacokinetics and dosing schedules will be discussed.

[Experimental studies on pharmacokinetics and tissue concentration of cis-dichlorodiammineplatinum (II) (CDDP) by intra-arterial infusion with hemostasis]

We have combined intra-arterial infusion with tourniquet techniques that produce hemostasis at the periphery of a tumor to accelerate penetration and adherence of the antitumor drug in the tumor. In the present study, MRMT-1 breast cancer was transplanted into the distal end of the femur of S-D rats to produce a bone tumor. Then cis-dichlorodiammineplatinum (II) (CDDP) was given in three ways: 1) systemic administration, 2) local intra-arterial infusion and 3) intra-arterial infusion with hemostasis, and the CDDP levels were determined of the tumor, kidney, lung and blood. The intra-tumoral CDDP level was found to be the highest in the group maintained with hemostasis, but that there was no significant difference in the levels in blood, the kidney and the lung among the three ways of administration. It was thus inferred that, though this method is effective in elevating the intra-tumoral CDDP level, sufficient hydration is necessary to prevent the same side effects as the other two methods.

Liposomes as drug carrier system for cis-diamminedichloroplatinum (II). II. Antitumor activity in vivo, induction of drug resistance, nephrotoxicity and Pt distribution

In this study we have investigated the use of liposomes as a drug carrier system for cis-diamminedichloroplatinum(II) (cis-DDP) in order to reduce the nephrotoxicity with preservation of antitumor activity. Liposomes (PC/PS/Chol 10:1:4) were prepared using hydration media containing no or a relatively low concentration of NaCl. It was found that cis-DDP containing liposomes (lip cis-DDP) injected i.v. to IgM immunocytoma-bearing LOU/M rats at a dose of 1 mg cis-DDP/kg (cumulative dose 7 mg cis-DDP/kg) showed less antitumor activity than the free drug. The optimal cumulative dose of free cis-DDP for induction of antitumor activity in this tumor system is 7 mg/kg (7 X 1 mg/kg). At a dose of 2 mg lip cis-DDP/kg (cumulative dose 14 mg cis-DDP/kg) the antitumor activity could not be increased by choosing another phospholipid composition of the liposomes [DPPC/DPPG/Chol (10:1:10)]. cis-DDP incorporated in DPPC/DPPG/Chol liposomes showed a similar antitumor activity to cis-DDP incorporated in PC/PS/Chol liposomes. After an i.v. dose of 2 mg lip cis-DDP/kg (PC/PS/Chol) kidney damage was less compared to the treatment with free cis-DDP (1 mg/kg). However, after a single dose of 2 mg cis-DDP/kg or a cumulative dose of 8 or 16 mg cis-DDP/kg, kidneys of rats treated with lip cis-DDP contained twice as much Pt as after treatment with free cis-DDP. Moreover, after treatment with lip cis-DDP, a twofold increase of the amount of Pt in tumor tissue was measured. In vitro studies with Pt recovered from spleens obtained from rats treated with lip cis-DDP i.v. showed that based on the equal amounts of Pt recovered the antitumor activity of the recovered Pt was reduced, indicating inactivation of cis-DDP in vivo. As during treatment with free cis-DDP, recurrence of the tumor was observed during the continued treatment with lip cis-DDP. It was found that these recurrent tumors were resistant to further therapy with cis-DDP. In conclusion, cis-DDP encapsulation into liposomes decreased the nephrotoxicity. The antitumor activity of cis-DDP is preserved by liposome encapsulation when it was used at a dose of 2 mg/kg, but it was reduced in terms of earlier onset of regrowth.

Serial determination of platinum, protein content and free sulfhydryl levels in plasma of patients treated with cisplatin or carboplatin

We report here the results of serial determinations of free-sulfhydryl, protein content and platinum levels in plasma of cancer patients following either cisplatin (cis-DDP, 3 patients, 60 mg/m2) or carboplatin (JM-8, 3 patients, 300 mg/m2) i.v. administration. After treatment with cis-DDP, significant platinum binding to plasma components with MW greater than 25 kD was observed; the ratio free-sulfhydryls/protein content decreased during the first two hours, returning to normal values at 24 hours after injection. In contrast, no evidence of platinum binding to plasma components with MW greater than 25 kD was noted after JM-8 i.v. administration, and the ratio free sulfhydryls/protein content did not change significantly after treatment. In vitro experiments show that at a molar ratio cis-DDP:JM-8 1:10, the two compounds bind to low MW thiols with the same kinetics. These data seems to suggest different interactions at the plasma level of these drugs, which may be correlated with their different toxicity.

Collagen chemoembolization: pharmacokinetics and tissue tolerance of cis-diamminedichloroplatinum(II) in porcine liver and rabbit kidney

Pharmacokinetics of chemoembolization with a fibrous collagen carrier was studied in rabbit kidney and porcine liver models. Cisplatin (1 mg/ml) chemoembolization of liver and kidney was compared with i.v. and intraarterial cisplatin infusion. Tissue platinum concentration [Pt] was measured at 2.5 h by atomic absorption spectrometry. Renal platinum retention and Angiostat (collagen for embolization) concentration were linearly related (r = 0.87, p less than 0.001). At 10 mg/ml collagen for embolization, chemoembolized kidney [Pt] was 220 +/- 50 (SE; n = 4) times contralateral kidney [Pt], and 62 and 23 times renal [Pt] by i.v. and intraarterial infusion, respectively. At 10 mg/ml collagen for embolization, chemoembolized liver [Pt] was 2 times hepatic [Pt] by i.v. and intraarterial infusion. Since hepatic tumor vasculature is end arterial, chemoembolization should yield high [Pt] in tumor (as in kidney) but lower levels in normal liver.

Pharmacokinetics, toxicity, and short-term results of cisplatin hyperthermic isolated limb perfusion for soft-tissue sarcoma and melanoma of the extremities

Fifty-nine patients with melanoma or soft tissue sarcoma of the extremities underwent hyperthermic isolated limb perfusion utilizing cisplatin and wide local excision. Doses of cisplatin ranged from 0.75 to 2 mg/kg. The mortality and morbidity rates were 0 and 6.8 percent, respectively. Pharmacokinetic studies indicate that cisplatin is rapidly bound to perfused tissues and remains bound for 1 month. Maximum tumor response in sarcomas occurs 1 to 2 weeks after perfusion, compared with 1 month after perfusions with l-phenylalanine mustard and actinomycin D. Local and regional recurrence rates were 0 and 3.4 percent, respectively, at 1 year. Further studies of hyperthermic limb perfusions with cisplatin are warranted.

The effects of platinum levels in plasma, urine, and kidney on blood urea nitrogen levels after cisplatin injection in rats

To analyze the relationship between the kinetics of filterable Pt and nephrotoxicity after cisplatin injection, Sprague-Dawley rats were given 5 mg/kg of i.v. cisplatin during hypothermia (hypothermia group) or given 5 mg/kg of cisplatin preincubated with rat serum (preincubation group). Plasma Pt levels, kidney Pt contents, urinary excretion of Pt, and blood urea nitrogen (BUN) levels after cisplatin injection were then determined. These hypothermia and preincubation treatments were performed in order to change the kinetics of filterable Pt without changing the total dose of cisplatin. Plasma Pt levels were significantly changed by both hypothermia or preincubation. Urinary excretion of Pt was unaffected by hypothermia but was significantly reduced by preincubation. However, significant differences in BUN elevation were not observed either in the hypothermia group or the preincubation group relative to the control group. Kidney Pt contents were not affected by hypothermia or preincubation at 1 h, 6 h, and 24 h after cisplatin injection. When rats were injected i.v. with 5, 7, or 10 mg/kg cisplatin, dose-related increases were observed both in kidney Pt contents and in BUN levels. These results suggest that the degree of nephrotoxicity more accurately correlates with renal Pt content rather than with plasma Pt levels or urinary concentration of Pt, and that the role of filterable Pt species in producing nephrotoxicity may have to be reevaluated.

Pharmacokinetics of free and total platinum species after rapid and prolonged infusions of aqua (1,1-bis(aminomethyl)cyclohexane) sulfatoplatinum (II) (spiroplatin) during a phase I trial

The pharmacokinetics of the second generation platinum complex aqua(1,1-bis-(aminomethyl)cyclohexane)sulphatoplatinum(II) (spiroplatin, TNO-6) were studied during a phase I evaluation. Thirty patients received 49 cycles of spiroplatin by short term (less than or equal to 10-min), 1-, 3- or 6-h infusion. Dosages given ranged from 5 to 40 mg/m2. Platinum determinations were performed by atomic absorption spectrometry. Up to 5 days after administration platinum concentrations in plasma decayed triexponentially. Pharmacokinetic parameters of total platinum in plasma after short-term and prolonged infusion were similar in terms of terminal half-life (3.7 +/- 1.1 and 3.6 +/- 0.5 days), AUC/dose (548 +/- 106 and 616 +/- 278 min.m2/l), volume of distribution (20 +/- 6 and 27 +/- 81) and total body clearance (2.9 +/- 1.0 and 3.4 +/- 1.8 ml/min), whereas peak plasma concentrations were two times lower after prolonged infusion. The cumulative urinary platinum excretion after short-term infusion was 20 +/- 6%, 30 +/- 6% and 47 +/- 7% of the administered dose after 6, 24 and 120 h, respectively. These values are comparable to those after administration of cisplatin. The half-life of ultrafilterable platinum was 4.4 +/- 0.7 min. The curves of free and total platinum diverged rapidly, reflecting the high reactivity of spiroplatin towards plasma proteins. This high reactivity, most likely caused by the abundant presence of aquated compounds in the injection fluid, may also account for severe and unpredictable nephrotoxicity induced by spiroplatin.

Platinum concentrations in human autopsy tumor samples

Platinum concentrations were determined in autopsy tumor samples obtained from 27 patients who had received cisplatin 40-1,029 mg/m2 from 0 to 240 days antemortem. Liver metastases had significantly higher platinum concentrations than did tumors in other sites (p less than 0.005). Platinum concentrations in liver metastases were similar to platinum concentrations in normal liver. Platinum concentrations in gliomas and brain metastases were similar to platinum concentrations in other extrahepatic tumors. Platinum concentration generally decreased with increasing distance into brain from tumor. By multiple stepwise linear regression analysis, the factors that were independently most closely associated with tumor platinum concentration were time from last cisplatin treatment, cumulative lifetime dose of cisplatin, route of cisplatin administration (intraarterial vs. other), and site of tumor deposit (liver vs. other) (r = 0.69, p less than 0.001). Patients whose tumors had responded to cisplatin-containing regimens had mean tumor platinum concentrations that were higher than the mean tumor platinum concentrations in patients whose tumors had not responded to cisplatin (p less than 0.05).

Serum and tissue levels of platinum after cisplatinum instillation of the rat bladder

The absorption of chemotherapeutics after local application in the urinary bladder is important for optimum therapy. We therefore investigated the absorption of Cisplatinum (Pt) through the bladder wall in 100 female Sprague-Dawley-rats after instillation under different clinical and pharmacological conditions. Only low platinum (Pt)-concentrations of about 1 microgram/ml could be detected in the serum using unmodified Cisplatinum solutions for instillation in the rat bladder indicating a rather low absorption rate for Cisplatinum. The extent of the absorption of Cisplatinum through the instilled bladder increased with the instilled volume. The absorption rate also increased after electrocoagulation and during cystitis with a maximum concentration of about 2.64 micrograms/ml. Correspondingly the vesicoplasmatic gradient factor clearly decreased. On addition of the detergent Tween 80, the serum Pt-concentration increased rapidly during the initial 30 min. Under these conditions Cisplatinum penetrated the bladder wall, about three times more effectively than in the absence of Tween while entering the systemic circulation only at about twice the normal rate without Tween 80. On addition of the polar organic solvent dimethylsulfoxide (DMSO) serum Pt-concentration increased continuously during the following 2 to 3 h reaching maximum values of about 13.3 micrograms/ml. The greatest accumulation of Pt in the bladder tissue (about 1,600 micrograms Pt/g tissue) was also observed under these conditions. A comparison of the Pt-concentration in serum with that in the bladder wall showed the most favourable relation of high tissue penetration and low serum concentration using Tween 80.

Clinical pharmacokinetics of carboplatin

The pharmacokinetics of carboplatin were investigated in cancer patients after single, IV infusion doses of 75, 150, 247.5, 300, 375, and 450 mg/m2. Total plasma and urine platinum and plasma ultrafilterable platinum concentrations were determined by atomic absorption spectrometry. Carboplatin was analyzed in plasma by a specific high-performance liquid chromatography (HPLC) procedure. Total plasma platinum, which represented free carboplatin, protein-bound platinum and metabolites, declined triexponentially; plasma half-lives (t1/2 lambda 1, 0.2 to 0.4 hr; t1/2 lambda 2, 1.3 to 1.7 hr; t1/2 lambda 3, 22 to 40 hr) and total body clearance (CLTB 2.8 +/- 0.5 L/m2/hr) were dose independent. Maximum plasma concentrations (Cmax) and area under the plasma concentration time curve (AUC) increased proportionally with dose. Plasma ultrafilterable platinum and carboplatin concentrations at doses of 375 and 450 mg/m2 declined in a biphasic manner. Plasma carboplatin elimination (t1/2 lambda 1, 0.50 hr; t1/2 lambda 2, 2.2 hr) and CLTB (4.4 to 5.6 L/m2/hr) were also independent of dose; AUC and Cmax increased proportionally to dose. Plasma free platinum was essentially all carboplatin for 8 or 12 hours after administration. Carboplatin did not bind to plasma protein in vitro but did degrade (t1/2-26 hours) to yield a reactive intermediate that bound rapidly and irreversibly to protein. The long terminal elimination half-life of plasma platinum was associated with irreversible binding of a platinum metabonate to plasma protein. The urinary excretion of platinum (0 to 24 hours) accounted for 58 to 72% of doses in 12 to 24 hours. The remainder of the dose is slowly excreted. The pharmacokinetics, in vivo stability, protein binding, and elimination of carboplatin are distinct from the first-generation analog cisplatin.

[Intraperitoneal (Ip) administration of cisplatin in combination with systemic chemotherapy in patients with malignant ascites of gastrointestinal cancer: clinical evaluation and pharmacokinetics]

Ten patients with carcinomatous peritonitis of gastrointestinal cancer have been treated with administrations of CDDP-Ip (50-150 mg/body), in combination with systemic chemotherapy simultaneously combined with sodium thiosulfate (STS) iv in 4 patients. All patients received transfusions of specific hydration. The pharmacokinetics of CDDP was studied in 4 patients, and the following results were obtained. (1) As for its effect on malignant ascites, according to Koyama's and Saito's criteria, 2 patients showed a complete response, 3 showed a partial response, and 5 showed no change. (2) As for its effect on the primary site, only one patient showed a partial response, and the others no change. (2) As to its side effects, 6 patients manifested nausea and vomiting, and only one showed a mild kidney dysfunction, and no myelosuppression. No significant difference in the side effects between the STS-combined group and the non-STS-combined group was found. (3) Serum CDDP levels were reached maximum 1-2 hours after Ip, and gradually decreased during the beta-phase of iv administration. Significant levels of non-protein-bound CDDP were found in the serum within 4 hours after Ip. These results indicate that the CDDP Ip is safe and useful for carcinomatous peritonitis of gastrointestinal cancer, however the combination of STS might weaken the systemic anti-cancer effect of CDDP by neutralizing the non-protein-bound CDDP in the serum.

[Antitumor effect of UFT on human ovarian cancer grafted to nude mice and 5-FU concentration in tumor and normal tissues]

Antitumor effects of UFT, tegafur (FT-207), cisplatin (CDDP) and the combination of UFT with CDDP on a human ovarian cancer xenograft in nude mice and the concentration of 5-FU in the tumor tissue and major organs were studied. UFT (48.6mg/kg/day X 20) or tegafur (15.0mg/kg/day X 20) was daily administrated orally, and CDDP (5mg/kg/day X 3) was administrated intraperitoneally at an 7-day interval. The inhibition rates of the tumor growths were 49.6% with UFT, -2.3% with tegafur and 17.7% with CDDP, respectively. In the combination of UFT with CDDP, severe side effect were observed. The concentration of 5-FU in UFT-treated group was higher than tegafur group: about 2 times in the tumor, 5 times in the liver, 9 times in the kidney and 4 times in the spleen, respectively. In the combination of UFT with CDDP, the concentration of 5-FU in major organs, especially in the kidney, in nude mice that died at 10 day after drug administration were higher than in those of UFT. These findings indicate that UFT increases the intratumoral concentration of 5-FU to elicit better antitumor effect and also the concentration of 5-FU in various normal organs after long time administration.

[Platinum concentrations in human tissue after administration of cisplatin]

Using flameless atomic absorption spectrophotometry, platinum concentrations in tissue samples were determined to clarify the distribution and accumulation of platinum in the human tissue after administration of cisplatin. Tissue samples were obtained at the time of autopsies or operation from 14 patients who were given cisplatin 0.7-20.1 mg/kg. Platinum concentrations were highest in the liver and testicle, high in the kidney, lung, heart and spleen, and lowest in the brain. In most organs except the brain, the tissue platinum concentrations increased exponentially according to the total dose of cisplatin. Platinum concentrations in metastatic tumors were generally somewhat lower than those in the normal parts of the organs, with the exception of cerebral metastasis. However, some of the metastatic tumors in the lung and brain showed higher concentrations than those in normal parts of the lung and brain, respectively.

Comparative distribution and excretion of carboplatin and cisplatin in mice

The comparative distribution and excretion of Carboplatin (cis-diammine-1,1-cyclobutane dicarboxylate platinum II, CBDCA, JM8) and cisplatin have been investigated in Balb C- mice following i.v. administration of the maximally tolerated doses (MTDs) of the compounds. Although the concentrations of platinum in the plasma and tissues during the alpha-phase were much higher for Carboplatin than for cisplatin, reflecting the difference in the doses used (4 vs 80 mg/kg), the tissue-to-plasma ratios were similar. During the beta-phase (1-10 days), however, both the platinum concentrations and the ratios were found to be similar for most tissues when cisplatin and Carboplatin were compared. The platinum concentrations and the tissue-to-plasma ratios of the spleen, brain, muscle, testes, ovary and bile, on the other hand, were consistently higher (two- to sixfold) after Carboplatin than after cisplatin. The highest ratios (greater than 20) were found in the kidney, liver, spleen (after Carboplatin only) and skin at 6 days after treatment. Comparison of the two compounds showed that the half-lives of platinum in the plasma and tissues during both the alpha- and beta-phases were similar, except for the spleen, in which a nine-fold greater t1/2 beta was recorded for Carboplatin than for cisplatin. The main route of excretion for the two complexes is via the kidneys, with 52% of cisplatin and 93% of Carboplatin being excreted during the first 3 days. The major part of this, however, is excreted within the 1st day. These results indicate that, although there are quantitative differences, the distribution and excretion profiles are similar for Carboplatin and cisplatin.

Correlation between free platinum AUC and total platinum measurement 24 h after i.v. bolus injection of cisplatin in humans

The plasma kinetics of platinum after i.v. bolus administration of cisplatin was determined for 17 patients with advanced cancer. Statistical analysis of individual values revealed a high correlation between the area under the plasma concentration-time curve (AUC) of free platinum (unbound to proteins) and the concentration of platinum bound to plasma proteins 24 h after drug administration (Cp24). A similar correlation was found between the peak plasma values of ultrafiltrable platinum (Cp0) and Cp24. When studied in the same patient, increases in free platinum AUC and Cp0 were also found to result in increased Cp24. It is suggested that a single measurement of plasma platinum concentration 24 h after i.v. infusion of cisplatin could be a simple method either of detecting patients with extreme values of AUC and Cp0 or of studying the evolution of these parameters during multiple courses of treatment, although it cannot be used to give precise values for AUC and Cp0.

[Study on changes in plasma platinum concentrations after administration of CDDP to maintenance hemodialysis patients]

Changes in plasma platinum concentration after administration of CDDP were studied in six patients on maintenance hemodialysis with malignancies. Plasma exchange was carried out on three patients for the purpose of plasmapheresis. A therapeutic dose of 51 mg/m2 of CDDP was administered to each patient without any severe adverse reactions. Plasma platinum concentration was measured by atomic absorption spectrophotometry, and the decay curve of the agent showed a biphasic pattern with an initial steep alpha phase and an ensuing mild beta phase in both hemodialysis patients and normal controls. As these patterns showed no renal excretion of CDDP, it was suggested that the uptake of CDDP into tissue was one of the main causes of the steep alpha phase. In patients given plasma exchange one or two hours after the beginning of CDDP administration, the reduction rates of plasma platinum were 74.7-61.7%, but the collection rate of the agent in the exchanged plasma was only 22.2-7.5%. These results indicated that the uptake of CDDP into tissue might occur rapidly within a few hours after CDDP administration.

Effect of methotrexate on the pharmacokinetics and renal excretion of cisplatin

The kinetics of platinum in plasma and erythrocytes, and its renal excretion, have been examined in five patients with non-small cell carcinoma of the lung, after treatment with cisplatin 50 mg/m2 (Platidiame) and, three weeks later, a combination of 50 mg/m2 cisplatin and 40 mg/m2 methotrexate. The patients were given 0.9% saline 1 l 1 h prior to drug application. Plasma platinum elimination was biphasic with a short initial phase (t1/2 alpha 10-31 min) and a long beta-phase (t1/2 beta 65-91 h). With the exception of increased AUC values in all five patients 0-8 h after the injection, no significant change in the kinetics of platinum in plasma was found after coadministration of methotrexate. In four of the five patients renal platinum excretion was reduced in the first 6 h after administration of methotrexate. The renal clearance of platinum was 50% lower in those four patients 0-3 h after the injection. With the exception of one patient, no signs of nephrotoxicity were observed after combined drug administration. Other toxic effects were mild and showed no increase after the initial administration of methotrexate.

Differential toxicity of cis and trans isomers of dichlorodiammineplatinum

Nephrotoxicity is the dose-limiting toxic effect of cis-dichlorodiammineplatinum (cis-platin) in humans. Its stereoisomer transplatin does not have any toxicity at equimolar concentrations, and it also possesses little antitumor activity. In this study, subcellular localization of both the platinum isomers was examined in the liver and kidney of the mouse 24 hours following the drug administration. Levels of the platinum isomers were measured using flameless atomic absorption. The results showed that higher concentrations of the cis isomer were localized in the liver and kidney, while the concentration of the trans isomer was higher in blood. This indicates that trans isomer is sequestered in the central compartment, whereas cis isomer is distributed in the organs. We also measured metallothionein mRNA and protein levels in both liver and kidney following cisdichlorodiammineplatinum and transdichlorodiammine-platinum treatment to distinguish if the differential toxicity of the two stereoisomers could be related to metallothionein induction. We report here that cisplatin was capable of inducing metallothionein expression in mice in vivo and that there is an inverse relationship between metallothionein expression and the pattern of tissue toxicity induced by the drug.

Comparative toxicity and renal distribution of the platinum analogs tetraplatin, CHIP, and cisplatin at equimolar doses in the Fischer 344 rat

Tetraplatin [tetrachloro(dl-trans)1,2-diaminocyclohexane platinum(IV), NSC-363812] is a new anticancer platinum drug analog targeted for clinical development because of its effectiveness against cisplatin-resistant tumor cell lines and its improved formulation. The toxicity of tetraplatin was compared at equimolar doses to that of cisplatin [cis-diamminedichlorophatinum(II)] and CHIP [cis-dichloro,trans-dihydroxybis-isopropylamine platinum(IV), NSC-256927]. Adult male Fischer 344 rats received an iv bolus injection of 6.7, 13.3, 26.7, or 53.3 mumol/kg of one of these drugs in saline and were killed on Day 1, 3, 5, 8, or 15 postinjection for assessment of toxicity with emphasis on evaluation of nephrotoxicity. Rats to be killed on Day 15 were housed in metabolism cages for daily urine collection. Tetraplatin was less nephrotoxic than cisplatin at equimolar doses; CHIP was not nephrotoxic at these doses. Renal platinum contents were similar after all three drugs and did not appear to be related directly to the nephrotoxicity. Nephrotoxicity was detected 4-5 days after 6.7 mumol/kg cisplatin, was localized to the corticomedullary junction, and progressed with time and dose. Tetraplatin-induced alterations of renal function were first observed after 13.4 mumol/kg on Day 4 as an elevation of urine volume (up to 10-fold) and a smaller elevation of urinary glucose excretion. Tetraplatin lesions were localized in the mid- and outer cortex and, even at the highest dose, were less severe than those observed with cisplatin. There were other prominent toxic effects of tetraplatin, such as gastrointestinal toxicity and myelosuppression, which indicate that factors other than comparative nephrotoxicity may impact the clinical potential of this new agent.

EDTA clearance in monitoring cisplatin dose escalation in patients with bulky metastatic germ cell tumors of the testis

A fast cisplatin clearance may reduce exposure time of tumor cells to the drug, and thus impair the expected effects of dose escalation. This hypothesis was tested in 23 patients with bulky metastatic germ cell tumors of the testis, treated with etoposide, bleomycin and high-dose cisplatin (60 mg/m2/24 h x 4). The daily dose was retrospectively calculated in mg/l EDTA clearance/24 h. A daily dose of 60 mg/m2 of cisplatin in a person with a body surface of 1.7 m2 and EDTA clearance of 100 ml/min was equivalent to 0.69 mg cisplatin/l EDTA clearance/24 h. In the whole group, 10 patients had complete remission (CR), 10 partial response (PR) and 3 progressive disease (PD). The mean daily cisplatin dose (mean) in the whole group was 0.86 mg/l EDTA clearance/24 h (range 0.35-2.00). For patients with CR, mean +/- SD was 1.00 +/- 0.46, for those with PR 0.80 +/- 0.44, and for those with PD only 0.61 +/- 0.07. A cisplatin dose over 0.86 mg/l EDTA clearance/24 h x 4 was obtained in 6/10 patients with CR versus 2/13 patients with PR + PD. Patients with PD received a significantly lower cisplatin dose than the whole group (0.61 versus 0.86 mg cisplatin/l EDTA clearance/24 h x 4.) The difference between the average toxicity grade after cisplatin dose over and below 0.69 mg/l EDTA clearance/24 h x 4 was significant only for leukocytes (WHO grade 2.17 versus 1.36). Thus, the effective escalated dose of cisplatin should preferably be calculated not per m2 body surface but per 1 liter EDTA clearance. The 'ideal' escalated dose might be about 0.86-1.0 mg cisplatin/l EDTA clearance 24 h x 4.