Chemosensitivity of human MCF-7 breast cancer cells to diastereoisomeric diaqua(1,2-diphenylethylenediamine) platinum(II) sulfates and specific platinum accumulation

Cisplatin, raceme-diaqua[1,2-bis(4-fluorophenyl)ethylenediamine]platinu m(II) sulfate (compound I), meso-diaqua[1,2-bis(4-fluorophenyl)ethylenediamine]-platinum(II) sulfate (compound II), and meso-diaqua[1,2-bis(2,6-dichloro-4- hydroxyphenyl)ethylenediamine]platinum(II) sulfate (compound III) were compared with regard to their effect on the MCF-7 breast cancer cell line in vitro. At equimolar concentrations (5 microM), cisplatin, compound I, and compound II were equiactive after 231 h drug exposure, whereas compound III was ineffective. Although compounds I and II showed markedly greater inactivation than did cisplatin after 6 h incubation with culture medium, compound I (but not compound II) exhibited antitumor activity equivalent to that of cisplatin when cells were exposed to the drugs for 6 h. Platinum measurements by neutron-activation analysis revealed that compound I was selectively and rapidly accumulated by MCF-7 cells, resulting in a high degree of DNA platination within the first few hours of drug exposure. However, when the drug-exposure period was long enough, platinum enrichment was not reflected in an overall difference in the cytotoxicity of compound I vs cisplatin. Nevertheless, compound I should be superior to cisplatin in vivo, provided that effective plasma levels can be maintained for about 6 h.

Relative lack of toxicity of transplatin compared with cisplatin in rodents

The differential toxicity of the cis- and trans-isomers of diamminedichloroplatinum (II) (cisplatin and transplatin) was investigated in rats and guinea pigs. In both species, repeated daily administration of 1 to 2 mg per kg cisplatin produced severe histological and/or functional damage to renal and gastro-intestinal systems and resulted in death of the animals. Quantification of tissue platinum by atomic absorption spectroscopy demonstrated accumulation of large amounts of platinum in the kidney of the animals, with lesser amounts in the liver and gastro-intestinal tract. Transplatin, administered at total doses two- to four-fold that of cisplatin, was essentially non-toxic by histological and functional assessment. However, the amounts of tissue platinum measured in transplatin-treated animals were no smaller than those measured in cisplatin-treated animals; indeed, platinum concentrations in kidneys of transplatin-treated rats were more than 2.5 times those in cisplatin-treated rats. Thus tissue platinum content did not correlate with organ damage. These data suggest that mechanism(s) involving steric interactions of platinum species, perhaps with cellular macromolecules such as DNA or RNA, may be important in the differential toxicity of these two compounds.

Clinical pharmacokinetics of carboplatin

Carboplatin [diammine(1,1-cyclobutanedicarboxylato)platinum(II)] is one of the most promising second generation platinum compounds. Its greater chemical stability in comparison with cisplatin accounts for its lower reactivity with nucleophilic sites of DNA, and may therefore be related to the higher dose necessary to obtain an antitumour effect similar to that of cisplatin. The lower reactivity with proteins may be related to the observed reduction in nephrotoxicity. Its dose-limiting toxicity is myelosuppression, especially thrombocytopenia. Total and ultrafilterable platinum are detected by flameless atomic absorption spectrophotometry, and high performance liquid chromatography with either UV or electrochemical detection is used for the quantification of carboplatin. These 3 species have been measured as a function of time in biological fluids and tissues to determine their pharmacokinetics. Carboplatin has high stability in infusion fluids in the absence of chloride, but it is less stable in plasma and urine. Protein binding is limited, while the low uptake in red blood cells appears to be species dependent. Commonly, carboplatin is administered intravenously, and its pharmacokinetics are linear up to a dose of 2400 mg/m2. In comparison with cisplatin, carboplatin has longer half-lives of ultrafilterable platinum (23 and 120 min versus 6 and 36 min for distribution and initial elimination half-lives, respectively) and a higher cumulative urinary platinum excretion (77 versus 28% of the dose in 24 h), both due to the lower protein binding of carboplatin. The terminal half-life of total platinum is comparable between the 2 compounds (5.8 versus 5.4 days). This value most probably represents the breakdown of proteins to which both compounds are irreversibly bound. Relationships between pharmacokinetics (area under the curve) and pharmacodynamics (extent of myelosuppression or extent of existing kidney failure) have allowed the development of equations for rational dosage reduction. Intraperitoneal administration has been used in cases of residual ovarian cancer: as a result of its higher hydrophilicity and higher molecular weight, carboplatin is cleared more slowly from the peritoneal cavity than cisplatin (6 vs 15 ml/min). The low bioavailability (4 to 12%) and the gastrointestinal side effects observed did not warrant further studies with oral administration. In contrast to results from animal studies, the modulation of carboplatin-induced myelosuppression by diethyldithiocarbamate (DDTC) was not clinically successful. Valuable alternatives may be the combination with WR2721 or colony-stimulating factors.

Intratumoural administration of cisplatin in slow-release devices: II. Pharmacokinetics and intratumoural distribution

The pharmacokinetics of cisplatin in mice with s.c. RIF 1 tumours was studied after intratumoural (i.t.) administration of drug in solution and in different slow-release devices. The data were compared with those obtained after i.p. administration of cisplatin. The slow-release devices under test were manufactured from either starch (ST) or polymeric hydrogels with different water uptakes (named T1, T2 and T3). In vitro release from these devices was approximately 100% in 2 h for starch rods, 100% in 24 h for T3 hydrogels, 45% in 4 days for T2 hydrogels and less than 10% in 4 days for T1 hydrogels. In vivo release rates agreed well with the in vitro data for T1 and T2 rods and were slightly slower in vivo for the T3 rods. The ST rods released the drug 6 times slower in vivo than in vitro. Plasma concentrations after i.t. administration were lower than those measured after i.p. administration. Systemic exposure to both total and free platinum was reduced to 70% for i.t. as compared with i.p. administration. Tumour concentrations were 4 times higher after i.t. than after i.p. administration. Tumour and peak plasma levels of platinum increased with increasing release rates. With the faster-releasing formulations (ST and T3), tumour platinum concentrations were 100 times higher than after i.p. administration. With the slower releasing formulations (T1 and T2), total tumour platinum concentrations were 2 and 9 times higher, respectively, than after i.t. administration of cisplatin in solution. Platinum distribution within the tumour was homogeneous after i.p. administration. After i.t. administration of cisplatin in solution, platinum concentrations in the centre of the tumour were approximately 4 times higher than in peripheral tumour tissue. Implantation of cisplatin in T2 and T3 hydrogel rods resulted in large concentrations of platinum in the centre of the tumour (the site of implant), which decreased steeply towards the tumour periphery. In summary, i.t. administration of cisplatin solution produced better results than did systemic (i.p.) administration in terms of tumour versus plasma drug-concentration ratios. Administration of drug in slow-release rods proved even more advantageous, although this was offset by inhomogeneous drug distributions within the tumour.

Renal damage in mice after sequential cisplatin and irradiation: the influence of prior irradiation on platinum elimination

Doses of 4-6 mg kg-1 c-DDP given 6 months before renal irradiation caused only a modest increase in functional radiation damage (DEF 1.1). These effects could be explained by additive toxicities and the damage was much less than when c-DDP was given 3-6 months after irradiation. Pharmacokinetic studies did not demonstrate any decrease in the rate of platinum elimination after previous low-dose renal irradiation.

Regional pharmacokinetic selectivity of intrapleural cisplatin

The pharmacokinetics and toxicity of cisplatin were investigated in 3 patients affected by malignant mesothelioma who received 90 mg/m2 of the drug intrapleurally. The mean area under the pleural Pt concentration versus time curve (AUC) [12.83 (S.D. 4.06) mg.min/ml] was about 50 times greater than that detected in plasma [0.27 (0.03) mg.min/ml], indicating a clear pharmacological advantage for this route of administration. The mean plasma total Pt concentration was 1.1 micrograms/ml and the apparent total body clearance was 268 (101) ml/min. Platinum plasma pharmacokinetic data measured following intrapleural cisplatin administration (4 patients) were compared with those observed in 7 patients treated intravenously with the same dose of cisplatin (90 mg/m2) under the same modalities of hydration. Intrapleural administration of cisplatin resulted in significantly lower plasma total partial AUC (P less than 0.05) and prolonged plasma levels of filterable Pt compared with intravenous administration. No difference between the two routes of cisplatin administration in the renal clearance (S.D.) of filterable Pt [132 (64) ml/min and 122 (39) ml/min for intravenous and intrapleural cisplatin, respectively] were observed. None of the mesothelioma patients developed clinical symptoms or signs of pleural inflammation. The intrapleural treatment did not produce haemotoxicity and the emetic toxicity was lower compared with that observed in patients receiving cisplatin intravenously.

Enhanced antitumor activity in mice after administration of thermosensitive liposome encapsulating cisplatin with hyperthermia

The antitumor effect of cisplatin-(CDDP)-encapsulated thermosensitive large unilamellar liposome (ThLip) administration with hyperthermia (HT) was examined in mice bearing Meth A fibrosarcoma. The tumor Pt levels after ThLip administration were increased in response to HT. The targeting index was approximately 3. The antitumor activity of ThLip + HT, as measured by tumor growth delay or tumor weight inhibition, was larger than that of ThLip without HT or a solution with or without HT. The CDDP dose in ThLip + HT to give equivalent tumor growth delay in solution (40 micrograms/mouse) + HT was about 10 micrograms/mouse, and therefore the targeted drug delivery enhancement ratio was about 4. The ratio correlates with the targeting index. The blood urea nitrogen level, as an indicator of CDDP nephrotoxicity, was increased 7 days after the administration of ThLip (40 micrograms CDDP/mouse) with HT. However, this blood urea nitrogen level rise was independent of the activity enhancement by the liposome. These findings suggest that the HT combined CDDP delivery system using ThLip can decrease the effective CDDP dose, thereby increasing its therapeutic index.

The influence of tumor cell density on cellular accumulation of doxorubicin or cisplatin in vitro

The effect of tumor cell density on the cellular pharmacokinetics of doxorubicin (DXR) and cisplatin (CDDP) was studied using MOLT-3 human acute lymphoblastic leukemia cells. As determined by the MTT assay, the growth-inhibitory effect of DXR was approx. 40 times lower when cell density was increased from 10(6) to 10(8) cells/ml (positive inoculum effect), whereas little or no influence of cell density was observed in CDDP-induced cell-growth inhibition. As measured by high-performance liquid chromatography using a fluorescence detector, the cellular accumulation of DXR showed 6- and 18-fold decreases after 1 h incubation when the cells were concentrated from 10(6) to 10(7) and 10(8) cells/ml, respectively. Only at low cell density (10(6) cells/ml) did the amount of DXR in the cells increase with increasing exposure times of up to 6 h. The DXR concentration in the supernatant that was separated from a cell suspension showing a density of 10(8) cells/ml fell to 20% of that obtained at 10(6) cells/ml. The metabolites of DXR, including Adriamycinol and Adriamycinone, were not detectable in the cell extracts or supernatants at any cell density examined. In contrast, the cellular accumulation of CDDP calculated from the platinum concentration, which was measured with a flameless atomic absorption spectrophotometer, was essentially identical at all cell densities examined; moreover, extension of the exposure period resulted in a linear increase in the amount of CDDP in the cells. CDDP concentrations in the supernatants were equally retained, irrespective of cell densities. These observations indicate that the positive inoculum effect shown in DXR-induced cell-growth inhibition results from the decreased cellular accumulation of the drug at high cell densities. We found no influence for cell density on the cellular accumulation of CDDP that might be relevant to the therapeutic potentiation of this drug at high tumor-cell density.

The effect of platinum complexes on human skin cells in vivo and in vitro

The effects of platinum complexes on human fibroblasts and keratinocytes have been investigated. Cytotoxic effects were observed at approximately 4 microM (cisplatin), 10 microM (carboplatin) and 15 microM (JM9) when cells were grown continuously in these agents. When applied topically to hairless mouse skin in vitro carboplatin was shown to penetrate the skin and give levels where a cytotoxic effect would be apparent. Using an in vivo model of epidermal hyperproliferation in the mouse, an antimitotic effect of a 1% and 5% topical carboplatin preparation was demonstrated. These results suggest that topical platinum complexes are of potential in the therapy of hyperproliferative skin diseases.

Uptake and retention of platinum in patients undergoing cisplatin therapy

Results of in vivo measurements of the platinum concentration in kidneys and tumours of patients treated with cisplatin for testicular carcinoma, head and neck tumours and brain tumours are presented. The measurements were performed with an x-ray fluorescence technique. Our earlier studies have shown that maximum platinum levels in kidneys were reached 3-4 h after an intravenous injection of cisplatin. The present study showed that, at that time, the ratio between the concentration of platinum in kidney and in blood serum was 22 +/- 7 (+/- 1 S.D.). Between 24 and 72 h after administration this ratio was 10 +/- 3, as shown in another group of patients. Measurements of platinum concentration in brain tumours showed varying maximum uptake, between 14 and 40 micrograms/g, 5-15 h after administration. There was an indication that radiotherapy may increase the uptake of cisplatin in normal brain tissue. The technique described can be used for further studies of the platinum concentration in tumours and risk organs in connection with cisplatin therapy. Such studies are needed to find out how to improve the therapeutic effects and lower the toxic ones.

Prediction of the antitumor activity of new platinum analogs based on their ex vivo pharmacodynamics as determined by bioassay

We report the predictive model for the clinical response of new platinum analogs against lung cancer by a bioassay using human lung-cancer cell lines including small-cell (SCLC) and non-small-cell lung cancer (NSCLC). Exponentially growing cells of six different SCLC and six NSCLC lines were exposed to different concentrations of the three platinum compounds, cisplatin, carboplatin, and 254-S in a double-agar colony-forming cell assay. The concentrations inhibiting 50% of colony formation (IC50 value) for cisplatin, carboplatin and 254-S in SCLC cell lines were significantly lower than those in NSCLC cell lines. A total of 15 patients entered the pharmacological study. In all, 80 mg/m2 cisplatin, 450 mg/m2 carboplatin, and 100 mg/m2 254-S were each given to five patients by intravenous drip infusion. Bioassay as well as chemical assay was achieved by clonogenic techniques using NCI-H-69 (SCLC cell line) and PC-9 (NSCLC cell line) as target cells. Biological comparison of antitumor activity was performed on the basis of the antitumor activity of patients' plasma using the antitumor index (ATI), which was defined as the area under the percentage of colony suppression versus time curve obtained by bioassay and calculated by the trapezoidal rule. When NCI-H-69 and PC-9 were used as target cells for bioassay, colony-inhibitory activity was revealed by the ATIs. The ATIs obtained by bioassay showed better correlation than the AUCs obtained by chemical assay with the clinical response for cisplatin and carboplatin against SCLC and NSCLC, according to the following equation: [Reported Response (%)] = 11.5668 + 0.0014 x [ATI] (r = 0.97). The response rates for 254-S against SCLC and NSCLC were predicted by this formula to be 40%-65% and 14%-16%, respectively. 254-S is prospectively suspected of having the same, if not more, activity then carboplatin against SCLC and of having almost the same activity as cisplatin against NSCLC.

Effect of bis(bilato)-1,2-cyclohexanediammineplatinum(II) complexes on lung metastasis of B16-F10 melanoma cells in mice

New platinum(II) complexes, bis(bilato)-1,2-cyclohexanediammineplatinum(II) which were lipophilic and water-miscible, were tested for antitumor activity against lung nodules from intravenously injected B16-F10 melanoma cells in C57BL/6 mice by intravenous administration of the complexes in water suspension form. Among them, DACHP(litho)2 and DACHP(urso)2 had high antitumor activity but others had no activity. The antitumor activity of DACHP(urso)2 was increased significantly by injecting it three times; T/C was over 280% with 100-day survivors of 3 of 6 mice tested. Large amounts of total platinum were found in lung and liver tissues by atomic absorption spectroscopy after single intravenous injection of DACHP(urso)2 suspension in ICR mice.

[Serum concentration and distribution in the liver, lung, heart and kidney of platinum after hepatic arterial injection in the form of cis-diammine dichloroplatinum microcapsule in rabbits]

After injection into the hepatic artery of New Zealand rabbits of microencapsulated CDDP (CDDPmc,group A) and non-encapsulated CDDP (group B), the platinum concentrations in sera and in the liver, lung, heart and renal tissues were determined and the hepatic and renal function monitored at various time intervals. The serum platinum concentration in group A increased slowly following administration of CDDPmc and gradually decreased after reaching its highest level. In contrast, it reached the maximum level immediately after the injection of CDDP and then decreased rapidly in group B, with the peak concentration being 4.5 times as high as that in group A. The hepatic tissues maintained a high level of the platinum for at least 21 days after the injection in group A, but for only a short period of time in group B. The platinum level was found to be low in the lung and heart tissues and high in the renal tissues in both groups, with the renal concentration being much higher in group B than in group A. The animals of both groups suffered some extent of hepatic and renal disfunction, but again, it was much more severe for animals in group B. The above results demonstrated that drug concentration in target tissues could be kept at a higher level, and in circulating blood at a lower level by the microcapsule technique than by the conventional administration technique, raising hopes that the therapeutic effect might be enhanced and the general side effects of CDDP reduced.

Phase I trial of 5-day continuous venous infusion of oxaliplatin at circadian rhythm-modulated rate compared with constant rate

The toxic effects and tissue uptake of both cisplatin and oxaliplatin--[(1R, 2R)-1,2-cyclohexanediamine-N,N'] [oxalato(2-)-O,O']platinum--were previously shown to vary similarly according to dosing time in mice. A 4-hour infusion of cisplatin resulted in fewer side effects and allowed administration of higher doses at 16 hours than at 4 hours in patients with cancer. We hypothesized that the continuous venous infusion of oxaliplatin for 5 days would be less toxic and would deliver a higher dose to the patient if the drug were infused at a circadian rhythm-modulated rate (peak at 16 hr; schedule B) rather than at a constant rate (schedule A). We tested this hypothesis in a randomized phase I trial. We escalated the dose of oxaliplatin to the patient by 25 mg/m2 per course. Courses were repeated every 3 weeks. An external, multichannel, programmable-in-time pump was used for the infusions. Toxicity was assessable for 94 courses in 23 patients (12 patients with breast carcinoma, nine with hepatocellular carcinoma, and two with cholangiocarcinoma). The incidence of neutropenia of World Health Organization grades II-IV and the incidence of distal paresthesias were 10 or more times higher (P less than .05) with schedule A than with schedule B. In addition, vomiting was 55% higher (P = .15) with schedule A than with schedule B. Furthermore, with schedule B, the mean dose of oxaliplatin (P less than .001) and its maximum tolerated dose (P = .06) could be increased by 15% over those doses with schedule A. An objective response was achieved in two of the 12 patients with previously treated breast cancer. We recommend that the dose of oxaliplatin for phase II trials be 175 mg/m2, delivered according to the circadian rhythm-modulated rate.

Characterization of a DNA damage-recognition protein from mammalian cells that binds specifically to intrastrand d(GpG) and d(ApG) DNA adducts of the anticancer drug cisplatin

A factor has been identified in extracts from human HeLa and hamster V79 cells that retards the electrophoretic mobility of several DNA restriction fragments modified with the antitumor drug cis-diamminedichloroplatinum(II) (cisplatin). Binding of the factor to cisplatin-modified DNA was sensitive to pretreatment with proteinase K, establishing that the factor is a protein. Gel mobility shifts were observed with probes containing as few as seven Pt atoms per kilobase of duplex DNA. By competition experiments the dissociation constant, Kd, of the protein from cisplatin-modified DNA was estimated to be (1-20) X 10(-10) M. Protein binding is selective for DNA modified with cisplatin, [Pt(en)Cl2] (en, ethylenediamine), and [Pt(dach)Cl2] (dach, 1,2-diaminocyclohexane) but not with chemotherapeutically inactive trans-diamminedichloroplatinum(II) or monofunctionally coordinating [Pt(dien)Cl]Cl (dien, diethylenetriamine) complexes. The protein also does not bind to DNA containing UV-induced photoproducts. The protein binds specifically to 1,2-intrastrand d(GpG) and d(ApG) cross-links formed by cisplatin, as determined by gel mobility shifts with synthetic 110-bp duplex oligonucleotides; these modified oligomers contained five equally spaced adducts of either cis-[Pt(NH3)2d(GpG) or cis-[Pt(NH3)2d(ApG)]. Oligonucleotides containing the specific adducts cis-[Pt(NH3)2d(GpTpG)], trans-[Pt(NH3)2d(GpTpG)], or cis-[Pt(NH3)2(N3-cytosine)d(G)] were not recognized by the protein. The apparent molecular weight of the protein is 91,000, as determined by sucrose gradient centrifugation of a preparation partially purified by ammonium sulfate fractionation. Binding of the protein to platinum-modified DNA does not require cofactors but is sensitive to treatment with 5 mM MnCl2, CdCl2, CoCl2, or ZnCl2 and with 1 mM HgCl2.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracorporeal hemofiltration: a model for decreasing systemic drug exposure with intra-arterial chemotherapy

Cisplatin (3 mg/kg) was infused through the hepatic artery in nine mongrel dogs. Four of these dogs underwent simultaneous extracorporeal hemofiltration (ECH) of the hepatic venous effluent using a high-flow, dual-lumen catheter placed in the vena cava at the level of the hepatic veins. Platinum levels were measured in the plasma, urine, and ultrafiltrate and in kidney and liver tissue. ECH significantly reduced systemic drug exposure as measured by the AUC for free and total platinum, by urinary excretion, and by 24-h kidney levels. Regional liver levels were minimally affected. Recovery of platinum in the ultrafiltrate was 40% +/- 14%. ECH resulted in efficient extraction of platinum and reduced systemic drug exposure with relative preservation of regional hepatic drug exposure.

Quantitative subcellular distribution of platinum in rat tissues following i.v. bolus and i.v. infusion of cisplatin

An analysis of the subcellular localization of platinum was conducted in Sprague-Dawley (SD) rats following administration of an i.v. dose of 6 mg/kg cisplatin (bolus and infusion). Biodistribution studies were carried out in the liver and kidney of control animals, as well as in these same organs and in the tumor (Walker 256 adenocarcinoma) of SD rats. The results obtained illustrate that in addition to the platination of DNA in these tissues, significant amounts of Pt are also incorporated into the chromosomal protein (CP) and cytosolic fractions. The localization of Pt in the cytosolic fractions was highest in the kidney, followed by the tumor, and lowest in the liver when determined as the fractional percentage of the total amount of injected drug (%ID/g). The significance of such cytosolic and CP localization of Pt is not known at this time, but they may be involved in the cytotoxic effects of cisplatin, as this drug is cytotoxic to tumors and kidneys but not to the liver. The localization of cisplatin in the subcellular fractions of liver, kidney, and tumor showed a trend toward being higher after i.v. infusion than after i.v. bolus administration of the drug.

L-methionine suppresses pathological sequelae of cis-platinum in the rat

The pathological changes characteristically observed in the kidney, bone marrow, thymus, spleen, and duodenum of the rat given 12.2 mg/kg of cis-platinum (CDDP) ip are reduced or eliminated when a CDDP solution containing a 20-fold excess of L-methionine to cis-platinum is administered. L-Methionine was also effective in reducing the renal toxicity induced by CDDP when given orally 20 min before the iv administration of 7.5 mg CDDP/kg. L-Methionine did not compromise the efficacy of CDDP when the antitumor activity of the combination of L-methionine and CDDP was measured against the Walker 256 carcinosarcoma in the rat. No significant reduction in the antitumor activity of the CDDP resulted from the parenteral administration of L-Methionine when evaluated against the L1210 murine leukemia. The oral administration of L-methionine (500 mg/kg) 30 min after the administration of CDDP has no significant effect on the antitumor activity of CDDP in mice bearing the L1210 murine leukemia. The results suggest that L-methionine may have some practical utility in the control of certain aspects of CDDP toxicity.

Platinum distribution in intraperitoneal tumors after intraperitoneal cisplatin treatment

The spatial distribution of platinum (Pt) in the kidney was studied by an autoradiographic technique, in which cisplatin (CDDP) was replaced by 195mPt-labeled CDDP, and by proton-induced X-ray emission (PIXE). Although both studies demonstrated comparable spatial distribution patterns, PIXE had the advantage that Pt concentrations could be determined quantitatively, in contrast to the relative information obtained by the autoradiographic technique. Using PIXE, the distribution of Pt in i.p. tumors was studied after i.p. administration of CDDP. The highest Pt concentrations were always found on the periphery of tumors, indicating that the periphery was exposed to a higher drug concentration than the center. Dose was correlated to the concentration of CDDP at both the center and the periphery (r = 0.99). The Pt concentration in the periphery was usually higher by a factor of 2-3 after i.p. administration than after i.v. treatment, whereas in the center of the tumor no concentration difference could be detected. The penetration depth of CDDP lay between 1 and 2 mm and was calculated from the differences in Pt concentration after i.p. and i.v. treatment. This indicates that the effective advantage of i.p. chemotherapy with CDDP in cases of cancers limited to the peritoneal cavity is accentuated at the periphery of the tumor.

Pharmacokinetics of cisplatin given at a daily low dose as a radiosensitiser

A total of 25 patients with inoperable cervical cancer were treated by daily radiotherapy (2 Gy); sensitisation was obtained by administration of 5 mg cisplatin 30 min before each irradiation session. The total cumulative dose of cisplatin varied between 50 and 150 mg. A complete kinetic profile (0-24 h) of platinum (Pt) was established after the first dose and at the end of treatment for 22 patients. Pt was quantified by atomic absorption spectrophotometry using Zeeman-effect background correction for trace analysis. The total Pt AUC0-24h increased from 1.53 +/- 0.77 to 7 +/- 3.55 micrograms.h.ml-1 between the start and the end of treatment (P less than 0.001). Ultrafilterable Pt (Pt UF) rose from 0.079 +/- 0.038 to 0.138 +/- 0.095 microgram.h.ml-1 (P less than 0.01). Elimination half-lives were unchanged for total Pt but rose for Pt UF; these kinetic modifications in Pt UF did not correlate with any significant change in individual serum creatinine levels. No clear correlation was found between the cumulative cisplatin dose and tumor levels measured in 13 patients, and the tumor cisplatin dose did not correlate with response to treatment. Patients with hematological toxicity were characterised by an increase in their residual Pt UF level during treatment. Overall, our findings strengthen the notion of Pt UF kinetic variability during repeated treatment.

Studies on age-dependent plasma platinum pharmacokinetics and ototoxicity of cisplatin

The age-related difference of cisplatin (CDDP) pharmacokinetics and ototoxicity were studied in 6 children with solid tumors who received CDDP infusion. CDDP was administered intravenously for 6 hours at a dosage of 30-120 mg/m2 and plasma-free platinum concentrations were determined by atomic absorption spectrophotometry. Plasma-free platinum concentrations ranged from 1.0 to 2.1 micrograms/ml at the end of infusions and declined rapidly with T1/2 of 0.6-1.5 hours. Pharmacokinetic parameters of plasma-free platinum were analyzed in 13 CDDP infusions by the one-compartment open model method. Parameters (Ke, Cl, T1/2 and Vd) of free platinum pharmacokinetics were 0.66 hr-1, 7.71l/hr, 1.35 hr and 15.71l in the younger group (age: 1.7-6.5 years old) and 1.44 hr-1, 11.41l/hr, 0.61 hr and 8.99l in the older group (age: 12.2-15.7 years old), respectively. Up to 600 mg/m2 of the cumulative dosage of CDDP caused minimal ototoxicity in the older group; however, in the younger group, hearing loss at a high frequency zone (6000 and 8000 Hz) began to appear at a cumulative dosage of 200 mg/m2 and progressed to middle zone (3000 Hz) when dosages surpassed 400 mg/m2. These data indicate that the pharmacokinetic difference in age possesses a large distribution volume (Vd) and that slower elimination of the drug in a younger age group is an important factor for age-dependent ototoxicity.

Comparison of the effects of intra-arterial and intravenous cisplatin on both limb tumor and lung metastases of transitional cell carcinoma RBT-1 in rats

The effects of intra-arterial (i.a.) and intravenous (i.v.) cisplatin on both limb tumor and lung metastases of transitional cell carcinoma RBT-1 in rats were compared. Tumor weights of limb tumors and the amount of lung nodules were evaluated on the eighth day after chemotherapy experiments. Both cisplatin 5 mg/kg i.a. and 5 mg/kg i.v. were administered to rats, but the intra-arterial method showed a significantly better effect on the limb tumor, whereas the intravenous method tended to be more effective on the lung metastases. Using the same dosage (5 mg/kg), the intra-arterial cisplatin group demonstrated a weaker level of nephrotoxicity and a smaller loss of body weight than seen in the intravenous cisplatin group. When a higher dose of cisplatin (6 mg/kg) was administered in the intra-arterial group, the antitumor effect on lung metastases and nephrotoxicity were similar to those of the group given cisplatin 5 mg/kg i.v. These data suggest that the dose of intra-arterial cisplatin can be slightly higher than that of intravenous cisplatin. Subsequently, a similar antitumor effect on lung metastases and a significantly better antitumor effect on primary tumor may be obtained at the equitoxic level.

Platinum incorporation and differential effects of cis- and trans-diamminedichloroplatinum(II) on the growth of mouse leukemia P388/D1

The parallel effects of cis-diamminedichloroplatinum(II) (1 microM) or trans-diamminedichloroplatinum(II) (20 microM) on the growth of mouse leukemia P388/D1 in culture, on the cellular content of protein/DNA, on the average cell volume, and on the distribution in different phases of the cell cycle were measured over a period of 70 h and compared with the amount of platinum residing in the cells. Despite different concentrations in the culture medium, similar amounts of cis- and trans-diamminedichloroplatinum(II) were incorporated. The platinum content of cells passed through an early concentration maximum in the millimolar range and decreased during prolonged times of incubation. Effects of cis-diamminedichloroplatinum(II) were marked and irreversible whereas those of trans-diamminedichloroplatinum(II) were small and transient. Proliferation was inhibited, while synthesis of protein and DNA continued almost unaffected. Cells were arrested in G2-phase of the cell cycle, and their volume increased correspondingly. The results suggested an inhibition of mitotic events, rather than of DNA replication, that caused cell arrest.

[An autopsy case of rectal cancer receiving cisplatin at total dose of 3.250 mg and platinum concentrations in autopsy tissue samples]

An autopsy case of a 57-year-old man who had received cisplatin, total dose of 3,250 mg (1,920 mg/m2) after proctectomy for advanced rectal cancer with hepatic metastasis is reported. Platinum concentrations in autopsy tissue samples are also reported. Cisplatin at a dose of 20-40 mg was administered intravenously once a week for 82 weeks, but renal failure did not occur. The patient died 529 days after his last cisplatin therapy, due to acute suppurative cholangitis. On autopsy, the hepatic hilar metastasis involved the bile duct, but the other metastasis of the liver became regeneration and necrosis, and the kidneys showed few findings but congestion and arteriosclerotic change. The spleen evidenced mild hemosiderosis. Tissue samples obtained at the time of autopsy were assayed for platinum using flameless atomic absorption spectrometry. The spleen had the highest concentration, about 2.7 times as high as that of the liver. The liver, the heart and the kidneys had high platinum concentrations (greater than 3.04 micrograms/g), but those of the jejunum and the ileum were low (less than 0.95 micrograms/g). Although cisplatin, FT 207 and krestin were effective for the rectal cancer, platinum was undetectable (less than 0.13 micrograms/g) in the ascending and the transverse colons.

[Effect of the portal vein injection of cisplatin and lipiodol on rat liver]

The purpose of this study was to elucidate the efficacy and safety of cisplatin powder, suspended in lipiodol, as a means for the treatment of liver cancer by injection into the portal vein. The effects of lipiodol (0.1 ml. 0.2 ml. 0.3 ml. 0.4 ml) alone, as well as that of cisplatin powder (1.0 mg) suspended in lipiodol or saline (0.1 ml), on the liver, was investigated by administration of them into the portal vein in 100 normal Wistar rats. The results revealed that the hepatic cells were moderately affected by a small amount of lipiodol alone, but a large amount of lipiodol caused multiple anemic infarctions in the peripheral area of the liver. And, also the injection of cisplatin powder suspended in lipiodol, compared to that suspended in saline, resulted in higher concentration of platinum in the liver. Histologically severe degenerative changes were also perceived in the liver, but these changes were reversible. These results suggest that cisplatin powder suspended in lipiodol is to be used for the treatment of liver cancer.