Endpoints for damage to normal tissues

Refinement of Experimental Procedures

Certain types of experiments using intact animals inevitably cause some suffering, ranging from psychological stress to physical pain or discomfort. The aim of refinement is to reduce such suffering to an absolute minimum, and if possible to eliminate it altogether. Ways of reducing environmental and handling stress, the use of anaesthesia and analgesia, the minimisation of aversive stimuli, the modification of severe endpoints, the limitation of survival times for animals with induced abnormalities, and the prediction of distress are discussed. It is essential that researchers recognise their animals as sensitive individuals, and that avoidance of animal suffering be regarded as a high research priority.

Radioprotective effect of sugar cane extract in chickens

To evaluate the radioprotective effect of sugar cane extract (SCE), SCE was orally administered into the crop of 3-week-old chickens for 3 consecutive days before or after x-ray radiation at a dose of 500 mg/kg/day. The survival rate of SCE administered chickens before x-ray radiation at a dose of 920 rad increased to 68.8% when compared with that of the irradiated control (50%). Histopathological examination revealed the intestine of SCE administered chickens to have mild to moderate pathological changes, when compared with that of the irradiated control animals.

Preoperative radiotherapy in rectal carcinoma--aspects of acute adverse effects and radiation technique

PURPOSE

To explain a possible association between treatment technique and postoperative mortality after preoperative radiotherapy of rectal carcinoma, the dose distributions were compared in model experiments.

METHODS AND MATERIALS

Preoperative radiotherapy with a three-beam technique delivered in five fractions to 25 Gy (5 Gy/daily for 5 or 7 days) was given to patients with primary resectable rectal carcinoma. The adverse effects of this treatment, both acute and late, have been low. In a parallel trial using an identical fractionation schedule and total dose but with a two-beam technique, the postoperative mortality was higher. Two-, three-, and four-beam techniques were analyzed in 20 patients with computed tomography based, three-dimensional dose planning. Dose distributions and dose-volume histograms in the planning target volume (PTV) and in the organs at risk were considered. A numerical "biological" model was used to compare the techniques.

RESULTS

The two-beam and the four-beam box techniques give the most homogeneous dose distributions in the PTV, although all techniques result in dose distributions that would be considered adequate, provided 16 MV or higher photon energies are used. Three- and four-beam techniques show advantages over the two-beam technique with respect to organs at risk, particularly the small bowel. With the two-beam technique and the upper beam limit at mid-L4, the volume of the bowel that receives > 95% of the prescribed dose, and hence, is included in the treated volume (TV), is more than twice as large as that with three- and four-beam techniques, and that of the total body between 1.5 and 2 times as large. The results of the analyses using the biological model indicate that the three- and four-beam techniques result in less small bowel complication rates than the two-beam technique. The integral energy to the total body is similar for all treatment modalities compared.

CONCLUSIONS

The volume of bowel included in the TV, rather than the energy imparted to the body, influences postoperative mortality, and emphasizes the importance of precise radiotherapy planning to minimize normal tissue toxicity.

Late changes in the normal mouse bladder after irradiation alone or in combination with cis-DDP or cyclophosphamide, assessed by stereological analysis

Stereological analysis has been performed to investigate the late changes in the normal mouse bladder one year after radiation alone (10-25 Gy) or radiation (10-15 Gy) combined with cyclophosphamide (CTX), 100 mg/kg, or cis-diamminedichloroplatinum (II) (cis-DDP), 6 mg/kg. A significant increase in total volume of urothelium was found in the group treated with CTX combined with radiation compared with the control. The total volume of connective tissue in the muscular layer in the groups which received X-rays only showed a significant increase compared to the control. There also seemed to be an increase in the amount of connective tissue in muscular tissue, although this was not statistically significant, in the groups treated with CTX and irradiation compared with CTX alone. This indicates the importance of radiation in the development of late damage. Results from bladders treated with cis-DDP alone or combined with radiation were statistically inconclusive due to the small number of animals in each group. The group treated with CTX and radiation (15 Gy) showed a significant decrease in the total volume of lamina propria, but no difference was found in the other treatment groups when comparing connective tissue, the muscular layer or the amount of vessels and capillaries with their corresponding control groups. Stereological analysis seems a feasible method to demonstrate late bladder tissue changes encountered after irradiation alone or combined with chemotherapy.

Early and late damage in the mouse bladder after radiation combined with cyclophosphamide or cisplatinum, evaluated by two different functional assays

Early and late changes in the reservoir function of the mouse bladder were investigated after irradiation alone or combined with cisplatinum (cis-DDP) or cyclophosphamide (CTX). Bladder function was repeatedly assessed from independent assays of urination frequency and cystometry. Treatments consisted of 10-30 Gy x-rays alone or 10-22.5 Gy combined with chemotherapy (cis-DDP 6 mg/kg i.p. or CTX 100 mg/kg i.p.). Within 30 days after treatment, early damage was detected by both assays but the correlation between assays was significant only in the group treated with x-rays and CTX. The late response was irreversible and a correlation was found (p < 0.05) between urination frequency and the results of the cystometry assay in all treatment groups. After x-rays alone or x-rays plus cis-DDP, the RD50 values (the radiation dose that induced a response in 50% of the animals) decreased with time as damage occurred. After x-rays plus CTX, maximum damage appeared much earlier and RD50 values tended to increase from 12 to 40 weeks. Comparison of these RD50 values gave a dose-effect factor (the ratio between the RD50 doses for x-rays alone and x-ray plus drug) of 1.1 to 1.3 for cis-DDP in both assays. The enhancing effect of CTX on bladder reservoir function was greater, especially in the results of the frequency assay, as indicated by considerably lower RD50 values. This resulted in an estimated dose-effect factor of up to 2.4. In conclusion, both assays are suitable for investigating early and late bladder damage, although the functional defect measured is different. Both CTX and cis-DDP increased early and late bladder damage when combined with irradiation. Late damage appeared earlier in combined treatment groups than in mice treated with irradiation alone.

Late radiation response of canine mediastinal tissues

The mediastinal tissues which included heart, lung, trachea and esophagus of 70 adult beagle dogs were irradiated to a range of total radiation doses between 24 and 68 Gy given in 2, 3 and 4 Gy fractions. The purpose of the study was the calculation of alpha/beta ratios for morphologic and functional changes of the mediastinal tissues. Functional assays including echocardiography, electrocardiography, right heart hemodynamics and cardiac output were performed. Histomorphometric analyses of all tissues included in the field were done 2 years after treatment. Euthanasia was performed on 7 of 70 dogs prior to 2 years due to congestive heart failure and seven other dogs had signs of heart failure 2 years after treatment. Heart failure was thought to be caused by either pericardial effusions or constrictive pericarditis in these dogs. Heart failure occurred at doses of 62 and 68 Gy given in 2 Gy fractions, 60 Gy given in 3 Gy fractions and 52 Gy given in 4 Gy fractions. The ED50 values for pericardial fibrosis for 2, 3 and 4 Gy fractions were 46.1, 43.9 and 26.6 Gy, respectively. An alpha/beta ratio of 2.5 Gy was calculated by direct quantal response analysis. Small foci of myocytolytic lesions were detected in 11 dogs. Calculated ED50 values for myocytolysis were 70.4 Gy given in 2 Gy fractions and 50.8 Gy given in 4 Gy fractions. The estimated alpha/beta ratio was 3.2 Gy. Heart rates determined from physical examination and frequency of S-T segment changes increased with increasing dose. No other dose related changes were found in any of the other functional parameters. Functional changes were detected in the 14 dogs with clinical signs of heart failure. Focal consolidation and subpleural fibrosis were present in the irradiated lung volume. These late changes had no detectable physiologic effect in these dogs because of the small volume of lung irradiated. The ED50 values for lung consolidation were 54.3, 45.8 and 26.6 Gy after 2, 3 or 4 Gy fractions, respectively. The estimated alpha/beta ratio was 3.4 Gy. No dose-related changes could be detected in the trachea or esophagus at 2 years after treatment. These results demonstrate that lung and pericardium are the most responsive tissues in the mediastinum within the first 2 years after treatment. Myocardial lesions were present with high ED50 values, but were not found to be functionally significant at 2 years after irradiation. Human clinical data indicate that longer observation periods are needed for development of these lesions.(ABSTRACT TRUNCATED AT 400 WORDS)

Cystometric evaluation of early and late irradiation damage to the mouse urinary bladder

The present study reports a simple, non-invasive, in vivo method for detecting early and late radiation damage to the mouse urinary bladder using transurethral bladder filling. The study also describes a useful experimental model for irradiation of mouse urinary bladder without any concomitant irradiation of the rectum and bony structures and maximal shielding of the small intestine. Within 30 days after single fraction bladder irradiation at 5-30 Gy, repeated cystometric investigations reveal a change in the reservoir function of the bladder illustrated by a considerable dose-dependent decrease in the compliance of the bladder wall. The changes in the reservoir function is reversible hence the bladder function is restored after another month. At various time intervals after the irradiation, however, the late radiation damage appears, the time of manifestation being dose-dependent. This final change is irreversible and consistent with the clinically known contracted bladder.

Bladder filling in mice: an experimental in vivo model to evaluate the reservoir function of the urinary bladder in a long term study

We report a simple, reproducible, and low-invasive in vivo method for repeated examination of bladder well properties in mice. Over a period of 21 days transurethral bladder fillings were performed every second day on the same animal. Analysis of the bladder volume at an intravesical pressure of 10 and 20 mm. Hg and at the leakage point showed no trend during the 21 day study period with regard to changes in bladder volume. The model has been applied to a group of mice treated with a single fraction bladder irradiation dose of 20 Gy. These mice were investigated repeatedly during the following year. The end point selected for data evaluation in the irradiated group of mice was a 50% decrease in bladder volume at an intravesical pressure of 20 mm. Hg relative to the control value (bladder volume before irradiation). The results clearly demonstrate a biphasic change in the bladder reservoir function, in the form of an acute, reversible change, a period of normalization and then a late irreversible damage. The latter stage is consistent with the clinically found contracted bladder. In a control group there was no significant change in bladder volume during the study period of more than 200 days. The model thus appears feasible for future studies of bladder irradiation damage.

Misonidazole-induced radio-resistance in normal and preirradiated jejunal mucosa

Pretreatment of mice with a single dose of whole-abdomen irradiation led to a relative decrease in radiosensitivity in jejunal crypts given a second single dose of irradiation 2 months later. Hyperbaric oxygen (3.5 bars) restored the survival level to initial values, suggesting that there was radiation-induced hypoxia in the primed jejunum. However, misonidazole did not sensitize primed jejunal crypts; it reduced the radiosensitivity of both normal and primed crypts. This 'paradoxical' effect of misonidazole could well be due to the acute toxic side-effects of 1 mg/g body weight misonidazole i.p., as there was a sharp drop in the core temperature of mice immediately after drug injection. Artificially maintaining the temperature of miso-treated animals at a normal level produced crypt survival levels similar to those of both normal controls and primed controls. Thus, although the primed gut is chronically hypoxic, as suggested by the effects of hyperbaric oxygen, misonidazole is not a reliable tool for the study of this tissue hypoxia. In all in vivo experiments with misonidazole, core temperature must be controlled in order to avoid misleading interpretations of experimental results.

Experimental studies on interactions of radiation and cancer chemotherapeutic drugs in normal tissues and a solid tumour

The interactions of radiation and seven cancer chemotherapeutic drugs have been investigated in four normal tissues (intestinal crypts, skin, haemopoietic tissue and lung) and in a solid C3H mouse mammary carcinoma in vivo. All experiments were carried out with male C3D2F1 mice. The investigated drugs were adriamycin (ADM), bleomycin (BLM), cyclophosphamide (CTX), 5-fluorouracil (5-FU), methotrexate (MTX), mitomycin C (MM-C) and cis-diamminedichloroplatinum(II) (cis-DDP). Single drug doses were given at different intervals before, simultaneously with and after single doses of radiation. The normal tissue reactions following drug-radiation combinations were found to be highly complex. The interactions varied both quantitatively and qualitatively from drug to drug and from tissue to tissue. The drugs enhanced the radiation response in most cases. However, signs of radioprotection was observed for CTX in skin and for MTX in haemopoietic tissue. The interval and the sequence of the two treatment modalities were of utmost importance for the normal tissue reactions. In general, the most serious interactions occurred when drugs were administered simultaneously with or a few hours before radiation. The radiation-modifying effect of the drugs deviated from this pattern in the haemopoietic tissue as the radiation response was most enhanced on drug administration 1-3 days after radiation. Enhancement of the radiation response was generally less pronounced in the tumour model than in the normal tissues. The combined drug-radiation effect was apparently less time-dependent in the tumour than in the normal tissues.

Actinomycin D and radiation: effects on mouse lung

The effect of actinomycin D (0.4 mg/kg) on radiation-induced lung damage in the mouse was investigated. The drug was administered either 4 weeks before, immediately after, or 16 weeks after single doses of 240 kV X-rays applied to the thorax of CBA mice. Lung damage was assessed by measuring respiration rate, with a whole body plethysmograph. Dose-response curves were obtained at 2-week intervals from 12 to 40 weeks after irradiation. Actinomycin D had no significant effect on respiration rate in this study. A summary of other experimental studies is included which shows conflicting results.

The predictive value of skin telangiectasia for late radiation effects in different normal tissues

Alterations in the microcirculation and parenchymal cell loss are common phenomena after irradiation of different organs. Whether parenchymal cell loss is a process well dissociated from vasculoconnective damage, or a consequence of this, is much debated. However, comprehensive radiopathological studies have shown that vasculoconnective tissue is an important common target for late effects in various organs. Scoring of skin telangiectasia was used by us as a clinical assay of late tissue effects after different dose schedules. All studies were done prospectively with standardized skin area, field size and radiation quality. The patients were scored regularly up to 10 years. The number of patients at risk for a prescribed score versus time was calculated with the life-table method. The late effects after 5 X 2.0 Gy/wk, in the dose range 40 to 70 Gy and after 2 X 4.0 Gy/wk, in the dose range 40 to 56 Gy have been established. The skin dose is 90% of the referred dose. Dose-response curves, relating the proportion of patients with a certain score at a fixed time and radiation dose and dose-latency curves, relating the latent period for a fixed proportion of patients with a certain score and radiation dose, were constructed. The analysis shows that: ED10/5 yr and ED50/5 yr for 5 X 2.0 Gy/wk is 50 Gy and 65 Gy, respectively, for distinct telangiectasia; The latent period, concerning both a certain frequency and degree of reaction, varies exponentially with dose level; The latent period for 50% of the patients, to obtain a certain score, LP50, is correlated to that for 10%, LP10, with LP50/LP10 = 2.2 +/- 0.2 (S.D.). This correlation is independent of score, total dose, and fractionation; Isoeffective doses for 5 X 2.0 Gy/wk and 2 X 4.0 Gy/wk, determined from the dose-response curves, resulted in the repair exp N between 0.31 and 0.32 and alpha/beta ratio between 2.9 and 3.1 Gy and determined from the dose-latency curves in exp N between 0.30 and 0.32 and alpha/beta ratio between 3.4 and 2.9 Gy. In conclusion, frequent and careful follow-up with registration of normal tissue reactions, until at least 10% of the patients have obtained the prescribed effect, is predictive for the further progression of the late effects. The fractionation characteristics for telangiectasia agree well with those for animal experimental morphological and functional endpoints for late effects in different organs and support the relevance of telangiectasia as a model for predicting late effects.

Interactions of drugs and radiation in haemopoietic tissue assessed by lethality of mice after whole-body irradiation

Drug-radiation interactions in haemopoietic tissue were assessed as the lethality of mice within 7-28 days after whole-body irradiation. The investigated drugs were adriamycin (ADM), bleomycin (BLM), cyclophosphamide (CTX), 5-fluorouracil (5-FU), methotrexate (MTX), mitomycin C (MM-C) and cis-diamminedichloroplatinum II (cis-DDP). The drugs were administered as single doses 15 min before graded doses of whole-body irradiation or at different intervals from 7 days before to 7 days after fixed radiation doses. ADM, CTX, 5-FU, MM-C and cis-DDP enhanced the radiation response when administered 15 min before irradiation. The dose effect factor (DEF) was 9.11 for 5-FU and in the range 1.25-1.59 for the other drugs. MTX administration 15 min before irradiation had no effect (DEF 1.00). However, MTX increased lethality if given 1-3 days after irradiation (DEF 1.21-1.76) and protected against lethality if given 1-3 days before irradiation (DEF 0.83). A similar time dependence was observed for ADM, CTX, 5-FU, MM-C and cis-DDP. Protection against lethality was not observed but in all these cases the lethality was significantly lower at administration 1-3 days before than 1-3 days after irradiation. A proper investigation of the effect of BLM was not possible as the combination of this drug and whole-body irradiation caused a high rate of gastrointestinal deaths.

Radiation induced renal damage in mice: influence of overall treatment time

The influence of overall treatment time on the radiation response of the mouse kidney was studied by varying the time over which 2 or 5 fractions of X-rays were administered. Two functional assays (urine output and 51Cr-EDTA excretion), and renal weight at sacrifice were used to obtain dose-response curves and estimate isoeffective doses. Split dose experiments showed Elkind recovery of about 5 Gy in 24 h. With a 7-day interval between fractions a transitory increase in isoeffect dose was observed in the first experiment. In the second, more extensive, experiment the recovered dose did not increase significantly even if the interval between two fractions was prolonged up to 25 days. Therefore, if slow repair occurred it was not worth more than 1 Gy because this was the limit of resolution of the assays used. As overall time was prolonged to 60 days an additional 1-2 Gy were recovered: it is difficult to explain this delayed sparing effect on the basis of a compensatory proliferative response, because the labelling indices of the likely target cells in the kidney are so low. Whatever the mechanisms involved, an increase in overall time had only a slight effect on isoeffect dose in these experiments and values for the "T" exponent were low (0.0-0.09). Recovery from sublethal injury between fractions has a much larger effect.

A preliminary report on the clinical application of fast neutrons in Krakow

The neutron therapy facility based on the cyclotron installed in the Institute of Nuclear Physics in Kraków, Poland, is described. Fast neutrons are produced by bombarding a beryllium target with 12.5 MeV deuterons. The unit has been used for treatment of cancer patients by the medical team of the Institute of Oncology in Kraków since September, 1978. Fifty-three patients were treated; most of these patients had advanced head and neck cancer. On the basis of the radiobiological experiments, a standard tumor dose of 1320 radn,gamma in 20 fractions over 4 weeks was established. From among 34 patients with advanced head and neck cancer, treated with neutrons only, and observed for at least one year, 10 patients, (29%) are living free of cancer.