Influence of cis-diamminedichloroplatinum (II) on mouse duodenal crypt stem cell survival after multifraction X ray treatment

The influence of platinum drugs on the radiation response of rat kidneys

The influence of a single bolus injection of platinum drugs on the radiation sensitivity of the kidneys was investigated in WAG/Rij rats. Drugs employed were cis-diammine-dichloroplatinum(II) (cisplatin, CDDP), cis-diammine-1,1-cyclobutanedicarboxylate platinum(II) (carboplatin, CBDCA) and cis-dichloro,trans- dihydroxy-bis-isopropylamine platinum(IV) (iproplatin, CHIP). Both kidneys were irradiated with a range of single X-ray doses while drugs were administered at 1 day or 1 week before irradiation. Maximum tolerated drug doses (defined as the LD1, the dose resulting in a mortality of 1%) were given. Damage inflicted upon the kidneys was monitored by determination of several parameters indicative of kidney function. Isoeffective radiation doses were calculated from these data for each treatment group at 4-8-week intervals up to 80 weeks following treatment. At each assay time, dose modifying factors (DMF) were calculated for each drug/radiation combination. The mean DMFs were highest for CDDP: approximately 1.6. Those for CBDCA and CHIP were lower: approximately 1.1 and 1.2, respectively. The CHIP DMFs were significantly different from unity. When the radiation was given in 4 or 8 daily fractions (4 fractions/week) the DMFs for CDDP were identical to those obtained with single doses. For CBDCA and CHIP, however, the DMFs after fractionated treatments were not significantly different from unity. Analysis in terms of the linear-quadratic (LQ) model indicated that not one of the three drugs had an effect on the alpha/beta ratio, and hence on the fractionation sensitivity of the rat kidney. Consequently, if these data are extrapolated to the clinical setting, the administration of these drugs at the maximum tolerated dose preceding a fractionated radiation treatment should not be expected to result in extra, unexpected, radiation toxicity of the kidney.

Combined modality treatment of the rhabdomyosarcoma R1H of the rat: influence of sequence of cisplatin and fractionated irradiation

The effect of irradiation with 30 fractions of 2 Gy in 6 weeks combined with a single dose of 5mg/kg cisplatin was studied in the rhabdomyosarcoma R1H of the rat and tumor response and normal tissue toxicity were assessed for various combinations of radiotherapy and chemotherapy. Cisplatin was given 3 days before, during (after the 5th and after the 10th fraction), or 3 and 17 days after radiotherapy. Five of the 12 tumors treated with cisplatin injected 3 days after radiotherapy were locally controlled (42%; 95% confidence intervals: 14-70%) as compared to 0/10 for radiotherapy alone (0%; 0-21%; p < 0.02). A similar trend was found for cisplatin injected 17 days after irradiation (2/6 local controls; 33%; 0-71%). With cisplatin given 3 days before radiotherapy 1/13 local controls were observed (8%; 0-22%; p < 0.05 when tested vs. cisplatin 3 days after radiotherapy). Tumor cure was dependent upon tumor size at time of cisplatin administration with 7/9 small tumors (< 2 mm3) cured versus only 2/35 cures of larger tumors (> 2 mm3). By contrast, net growth delay and skin damage were the same for combined modality treatment and for irradiation alone. General toxicity as assessed by body weight change was significantly higher for animals treated with cisplatin before or after radiotherapy, whereas cisplatin during radiotherapy showed equal effects as compared to radiotherapy alone. Although for the rhabdomyosarcoma R1H of the rat the combined modality treatment was shown to be more effective than radiotherapy alone when cisplatin was applied after radiotherapy, general toxicity was also higher for this mode of treatment.

Influence of cisplatinum on intestinal tolerance to photon and neutron irradiation in mice

The hypothesis that cisplatinum (c-DDP) interacts with radiation by inhibiting the cellular repair capacities, was tested by comparing the interaction of c-DDP with low-LET (60Co gamma-rays) and high-LET radiation (d(50) + Be neutrons) in mice. The biological endpoint was lethality, 6 days after total body irradiation (early intestinal tolerance). The dose modifying factor was 1.80 +/- 0.25 for c-DDP plus 60Co gamma-rays, and 1.97 +/- 0.3 for c-DDP plus neutrons. As less repairable damage is induced by fast neutrons than by photons, this suggests that, in this system, the interaction between radiation and c-DDP is not explained by repair inhibition but is purely additive.

Early and late effects of cisplatin and radiation at acute and low dose rates on the mouse skin and soft tissues of the leg

The influence of radiation dose rate and drug dose on the combined effects of cisplatin (Cis-diamminedichloroplatinum (II] and radiation on the skin and soft tissues was studied in the C3Hf/SED mice. Localized acute-dose-rate irradiation (ADRI) at 3.345 Gy/min and continuous low-dose-rate irradiation (CLDRI) of the hind leg at 0.028 Gy/min with and without the drug was delivered using a 137Cs laboratory irradiator. Cisplatin at 6 or 11 mg/kg was given by intraperitoneal bolus injection 1 hour before ADRI or by continuous infusion during CLDRI. Acute skin reaction was scored from days 13 to 30 and late skin contraction and leg contracture were measured at days 90, 180, 270, and 360 after treatment. A marked dose-rate effect was observed for these early and late normal tissue endpoints. At a dose of 60 Gy of CLDRI, the dose rate factor (DRF = isoeffect dose at CLDRI/isoeffect dose at ADRI) was 1.82 for acute skin reaction and 1.76 for late skin contraction or leg contracture at day 270. However, there was no significant enhancement of these early and late normal tissue effects by cisplatin at 6 or 11 mg/kg at either acute or low dose rates. Thus neither drug dose nor radiation dose rate had a significant impact on the combined effects of cisplatin and radiation on the mouse skin and soft tissues of the leg.

Intratumoural administration of cisplatin in slow-release devices. I. Tumour response and toxicity

In this study we investigated the effect of the incorporation of cisplatin in slow-release systems on tumour response and animal toxicity after intratumoural (i.t.) administration. Solid slow-release rods with incorporated cisplatin were prepared either from starch or from three different polyether-hydrogel formulations. In vitro release rates from these rods were widely different. With the starch system, approximately 100% release was obtained in 2 h. For the hydrogel formulations, release was approximately 100% in 1 day for a formulation with 40% water uptake (T3), 45% within 4 days for a formulation with 14% water uptake (T2) and 8% within 4 days for a formulation with 4% water uptake (T1). The slow-release rods containing graded amounts of cisplatin were implanted i.t. in s.c. RIF1 murine tumours. The i.t. administration of cisplatin in starch rods did not reduce animal toxicity or increase tumour response relative to i.t. injections of cisplatin in solution. For the hydrogel rods, the tumour response and animal toxicity for a given dose of cisplatin decreased with decreasing release rate. Higher doses of cisplatin could therefore be delivered with the slower-releasing hydrogel formulations. The slowest-release hydrogel rods (T1) had very little effect on either tumour (growth delay) or host (animal weight loss), even at cisplatin doses 8 times that tolerated as an i.p. injection. The fast (T3)- and intermediate (T2)-release hydrogel rods resulted in dose dependent tumour growth delays that were longer than those obtained with i.p. or i.t. administration of cisplatin. The highest response, a tumour growth delay of 55 days, was obtained with the intermediate-release hydrogel rods (T2) at a cisplatin dose of 40 mg/kg. Analysis of tumour growth delay for a given level of toxicity indicated that the intermediate-release formulation (T2) was slightly better than the fast-release formulation (T3) and confirmed the therapeutic advantage of i.t. implants over systemic therapy.

The effect of cisplatin on the repair of radiation damage in RIF1 mouse tumours in vivo

The effect of the antitumour agent cisplatin on repair of X-ray-induced damage was studied in RIF1 mouse tumours treated in situ. The response of tumours, assessed by growth delay, to 4 fractions of X-rays given at 5-h intervals was compared with that after single doses. The displacement between the curves was taken as a measure of repair. A single dose of 6 mg.kg-1 cisplatin given 0.5 h before the first fraction resulted in no detectable inhibition of repair despite a significant growth delay caused by drug alone. A dose of 2 mg/kg cisplatin given 0.5 h before each of the X-ray fractions did, however, cause some repair inhibition; a result confirmed by tumour control experiments. The schedule dependence for repair inhibition was the same whether the irradiations were carried out on clamped (fully hypoxic) tumours or under ambient conditions. Significant enhancement of radiation damage was seen after correcting for the effects of drug alone, whether or not repair inhibition occurred. The effects of cisplatin on normal stroma within the tumour (vascular damage) was also investigated by monitoring the regrowth rates of recurrent tumours. In contrast to the effects on tumour cells, no enhancement of damage or inhibition of repair was seen for this assay in the combined treatment schedules.

The influence of cisplatin on the response of mouse kidneys to multifraction irradiation

The aim of these studies was to measure the extent of renal damage after fractionated irradiation in combination with cis-diamminedichloroplatinum(II) (c-DDP) and to determine whether there was any drug-induced inhibition of repair of sublethal X-ray damage. Fractionated irradiations were given either in a short overall treatment time of 2 days or in a total time of one month, in which irradiations were given in the first and fourth weeks only. A single dose of c-DDP was given before the first X-ray dose for treatments in a total time of 2 days and before the first X-ray dose of each week for the split-course treatments. Renal function was measured at monthly intervals (from 18 to 39 weeks after the start of treatment) by clearance of 51Cr-EDTA. The renal damage was always worse after combined treatments (X + c-DDP) than after X-rays alone. A comparison of radiation dose-response curves with and without c-DDP yielded Dose Enhancement Factors (DEFs) of 1.2 to 1.4 for all fractionation schedules, with no trend for an increase in DEF with increasing number of fractions. A Linear-Quadratic (LQ) analysis of the data demonstrated that there was no change in the alpha/beta value for renal radiation damage for the combined treatments compared with X-rays alone (alpha/beta = 2-3 Gy). These results suggest that the increased renal damage which occurred after combined X + c-DDP was due to independent, additive toxicities and not to radiosensitization or inhibition of X-ray repair by the drug.

The influence of cisplatin and unilateral nephrectomy on the response of the rat kidney to irradiation

Cisplatin was administered as a single i.p. dose of 5 mg/kg to WAG/Rij rats at intervals of 7 days or 0.5 h before, or 7 days after graded X-ray doses to the left kidney. The right kidney was surgically removed 4 weeks after irradiation. Renal function was determined by measuring total urine volume excreted in 24 h, urine osmolality and serum urea. The severity of alterations in the various anatomic compartments of the kidney induced by the various treatments were graded histologically. The administration of 2 or 5 mg/kg cisplatin alone did not alter any of the kidney function parameters. Isoeffective radiation doses calculated for each of the functional parameters continuously decreased with increasing time after treatment. Differences between the isoeffective doses for the three combined treatments and for treatment with irradiation alone were only observed for urine osmolality and urine volume which primarily are tubular-related functional parameters. The histopathological grading studies also indicated that enhancement by cisplatin of radiation-induced damage was almost entirely confined to the tubules. The results of this study indicate that the sequence and length of time between treatments is an important variable in the development of cisplatin plus radiation-induced renal injury, but that none of the tested combinations showed a more than additive toxicity.

Carboplatin (JM8), etoposide (VP16) and thoracic irradiation for small cell lung cancer (S.C.L.C.): an evaluation of lung toxicity

Carboplatin (JM8) and etoposide (VP16) have demonstrated activity against a range of solid tumours. A retrospective study has looked for evidence of enhanced radiation pneumonitis when these drugs are employed in conjunction with irradiation. Twenty-nine patients with limited disease small cell lung cancer (S.C.L.C.) received JM8 (300 mg/m2) and VP16 (300 mg/m2) at intervals of 3-4 weeks for 4 cycles followed by thoracic irradiation. Twenty-one were evaluated and compared with 21 matched non-S.C.L.C. patients treated by radiotherapy alone. Patients were stratified into three groups according to the radiation dose schedule normalised using Wara's modification of Ellis' formula (n = 0.38, t = 0.06) [28]. Group 1 received less than 1014 rets, Group 2 1015-1250 rets and Group 3 greater than 1250 rets. Radiological pneumonitis was observed in 57% (12/21) of patients receiving combined modality treatment compared to 71% (15/21) of patients receiving radiation alone with evidence of a radiation dose-response relationship for the appearance of pneumonitis in both groups of patients (p greater than 0.1). In conclusion, no enhancement of radiation pneumonitis by carboplatin (JM8) or etoposide (VP16) has been observed.

Evaluation of mouse lip mucosa reactions after combinations of cis-diammine-1,1-cyclobutanedicarboxylate platinum (II) (CBDCA) and irradiation: single and fractionated treatments

The influence of CBDCA (JM8) on the radiation-induced mouse lip mucosal reactions has been tested. Both single and fractionated drug doses were used intraperitoneally at 60 mg/kg and 5 X 25 mg/kg respectively. A single injection of CBDCA did not alter the response to a single radiation dose, whether the drug was given at different time intervals from 24 hr prior, to 96 hr after irradiation. A concomitant treatment of daily CBDCA injections and irradiations for 5 consecutive days demonstrated no change of the capacity to repair sublethal radiation damage. When two equal sized radiation doses were separated by 10 days and CBDCA was administered daily from day 3 to 7, the ability to repopulate the lip mucosa epithelium during the radiation-free period was not influenced.

Additivity versus repair inhibition in fractionated treatments combining drugs and X rays: a theoretical analysis

Drugs which inhibit the repair of radiation damage could potentially be useful for enhancing the effects of radiotherapy. In pre-clinical combined modality studies, however, it is often difficult to state with certainty whether or not a drug has inhibited radiation damage repair. This paper shows that several commonly used parameters for assessing repair can give the wrong answer regarding the presence of drug-induced repair inhibition. These parameters are; the difference in radiation dose between 1 and n fractions to give the same effect, the fractional recovered dose per fraction interval, FR, and the related parameter FREC. A further parameter used for treatment comparisons is the enhancement ratio for the drug (D.E.R.; ratio of radiation doses, with and without drug, to cause a given effect). An increasing D.E.R. with increasing number of radiation fractions has been taken as an indication that the drug inhibited repair. The present report demonstrates that this, too, can be misleading. From an analysis based on a linear-quadratic survival curve for X rays, it is suggested that deriving and comparing alpha/beta ratios (ratio of the linea to quadratic coefficients) gives the best indication of drug-induced changes in survival curve shape which may reflect underlying changes in repair capacity.

Combined treatment of radiation and cisdiamminedichloroplatinum (II): a review of experimental and clinical data

Cis-diamminedichloroplatinum (II) (c-DDP), a highly effective cytostatic drug, is increasingly used in combination with irradiation both in the laboratory and in patients. This review aims at a critical reassessment of the potential role of this drug as a "radiosensitizer." The opinion about c-DDP being an effective hypoxic cell radiosensitizer in bacteria was substantiated in some studies on mammalian cells in culture but not in others. More powerful mechanisms of radiation enhancement, which are not yet fully explored, may be depletion of endogenous thiols, inhibition of cellular repair processes, and proliferation inhibition. The effects of c-DDP in combination with irradiation in experimental tumors seem to vary between different investigators and between different tumor systems. Occasionally, supra-additive effects have been observed in some animal tumors. This stresses the need for testing this combination treatment in various tumor types, preferentially of human origin. In normal tissues, the effects are, to a large extent, explained by independent cell killing by each agent. A substantial number of clinical pilot studies have shown that the combination treatment is feasible, but the results of ongoing phase III trials will be needed to assess the potential therapeutic benefit of this combined treatment modality.

Early and late damage in the mouse rectum after irradiation and cis-diamminedichloroplatinum(II)

The effects of radiation and cis-diamminedichloroplatinum(II) (c-DDP) in the mouse rectum were assessed using two functional endpoints (anal discharge/diarrhoea and body weight changes), one lethal endpoint (obstructive rectal stenosis) and a microscopic endpoint (semiquantitative histological scoring). After irradiation, anal discharge, diarrhoea and lethal rectal stenosis were found to be the result of submucosal fibrosis with a secondary mucosal ulcer due to mechanical damage by the faeces. Weight loss at both early and late times after irradiation seemed to be related to epithelial cellular depletion. c-DDP, when given in combination with X-rays, did not enhance the incidence of late anal discharge, diarrhoea or rectal stenosis. Using an arbitrary semiquantitative scale for measuring the degree and extent of late rectal injury, c-DDP sometimes seemed to postpone the expression of radiation damage in the rectum. This effect, however, might also be the result only of interexperimental variation. An increase by c-DDP in the early body weight loss after irradiation was also observed which could be explained by an additive effect in the rectal epithelium.

The effects of cis-diamminedichloroplatinum (II) and radiation on the proliferation kinetics of mouse duodenal crypt cells and on a partially synchronized crypt cell population

The effects of c-DDP and radiation, given alone or in combination, on the proliferation kinetics of mouse duodenal crypt cells were investigated by repeated labelling with 3H-thymidine. Crypt cells surviving a single dose of X-rays or c-DDP alone, appeared to proliferate faster than untreated controls. When both agents were given in combination, the proliferation rate of surviving crypt cells was markedly reduced as a result of a significant increase in the DNA synthesis time. The influence of the proliferation rate of crypt cells on the effects of c-DDP and X rays was analyzed using the crypt microcolony assay. Mice were given single doses or 2 fractions of X rays with 2 different time intervals (4 and 48 hours) either alone or in combination with c-DDP given 30 minutes before the second fraction. The lethal effect of the drug was approximately the same in cells that were in accelerated proliferation after the first irradiation as in unstimulated cells. A tendency for less cell killing by the drug was observed 3.5 hours after the first irradiation. To rule out cell age dependent effects of c-DDP, crypt cell survival was assessed after irradiation was given alone or in combination with the drug on a partially synchronized crypt cell population, obtained by repeated injections of hydroxyurea. A predominant lethal effect of c-DDP was found in cells in the late G1-phase. These findings are important to consider both from a mechanistic point of view as for clinical application of the agents.

Combinations of single doses and fractionated treatments of cis-dichlorodiammineplatinum (II) and irradiation: effect on mouse lip mucosa

Tolerance of the lip mucosa of NMRI mice to single and fractionated irradiation combined with cis-diamminedichloroplatinum (II) (cis-DDP) was investigated. For the various combination schedules total drug doses varying from 6 mg kg-1 to 13 mg kg-1 were injected i.p. It was found that cis-DDP did not alter the radiation sensitivity of this tissue at any of the time intervals tested (ranging from 24 h before to 72 h after single dose irradiations). When 5 daily drug injections were given concomitantly with 5 daily radiation treatments, a slight reduction of the lip mucosal reactions occurred, possibly due to partial synchronisation during treatment. No effect was seen when a single injection of cis-DDP preceded two irradiations given with increasing intervals up to 4 h. Both these combined fractionated treatment data suggest no inhibitory effect on repair of sublethal radiation damage. When repeated daily injections of cis-DDP were given in between 2 radiation doses separated by 10 days, no interference with repopulation could be detected. The present study also demonstrated an increase in systemic drug toxicity when cis-DDP was combined with irradiation, compared with that seen with either agent alone.

Dose and time effects of cis-diamminedichloroplatinum(II) and radiation on mouse duodenal crypts

The effect of cis-platinum and radiation on mouse duodenal crypts was assessed using the microcolony assay. The diameters of regenerating crypts were measured at various times after X-rays and cis-platinum given either alone or in combination. It appeared that the appropriate time of assay after any of these treatments was 88 h. When 10 mg/kg of cis-platinum was administered 24 h before, 0.5 h before or 10 min after radiation, the X-ray survival curve for crypt stem cells was shifted towards lower doses, with a Dose Effect Factor (DEF) of 1.2-1.3. When the drug was given one week before X-rays, no effect on the survival curve was observed. The slope of the X-ray survival curve was not modified by cis-platinum. When the drug was given within 6 h time of X-rays, the increased killing of crypt cells by cis-platinum was the same irrespective of the sequence of administration. These data suggest that cis-platinum and radiation kill crypt cells by independent cellular mechanisms. A survival curve for crypt cells was also obtained after graded doses of cis-platinum alone. It was characterised by a D0 of 3.18 +/- 0.40 mg/kg (1 S.E.) and an extrapolation number N of 2.9 X 10(4). When the drug treatment was combined with a single dose of X-rays, this survival curve was shifted towards lower drug doses without a significant change in the slope (D0 = 2.87 +/- 0.37 mg/kg). This suggests that independent killing of crypt cells by the two agents occurred over a wide range of drug doses.