M. Rezvani

A morphological study of radiation nephropathy in the pig.

Both kidneys of mature pigs received a single dose of 9.8 Gy 60Co gamma rays. Pigs were killed between 2 and 24 weeks after irradiation and the kidneys examined histologically. Glomerular and tubular changes were observed within 2 weeks of irradiation. Neutrophils and other leukocytes were seen within glomerular capillary loops; mesangial matrix and cell number increased. A progressive increase in thickening of the basement membrane and a decrease in capillary lumina were then noted. Basement membrane duplication occurred within 12 weeks. By 24 weeks these lesions had increased in severity, sclerotic endstage glomeruli, predominantly subcapsular or juxtamedullary, being evident. Tubular lesions initially consisted of focal areas of tubular atrophy in the juxtamedullary region. By 6 weeks subcapsular foci of tubular degeneration, regeneration, and necrosis were found; these appeared to resolve 12 weeks after irradiation. At later times the severity of the tubular lesions varied between pigs, with some exhibiting interstitial fibrosis involving a complete band of subcapsular tissue, while others showed relatively mild changes. There was no apparent change in the vasculature. These findings indicate that (a) there is no one target or dose-limiting cell, and (b) the vasculature does not play a primary role in the development of radiation nephropathy.

Radiation nephropathy in mature pigs following the irradiation of both kidneys.

Both kidneys in mature female Large White pigs, ca. 45 weeks old were irradiated with single doses of 7.8-14.0 Gy of 60Co gamma-rays. Radiation-induced changes in renal function were assessed on the basis of sequential individual measurements of kidney glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) for up to 24 weeks after irradiation. At the same time intervals blood samples were taken to determine plasma renin levels and the haematological status of each animal. Two weeks after irradiation the ERPF and in particular the GFR was increased. This was followed by a pronounced, dose-dependent, decline in renal haemodynamics. Minimal functional levels were observed 8-12 weeks after irradiation. Function then somewhat recovered. There was a significant (r greater than or equal to 0.98; p less than 0.001) inverse relationship between the mean values of GFR and ERPF, determined at 4-24 weeks after irradiation, and the radiation dose. After a dose of 7.8 Gy the reduction in ERPF was greater than that for GFR. However, at higher doses both parameters were reduced to an equal extent. The resulting slope of the dose-effect curve for impaired renal function versus dose was significantly steeper for GFR than that for ERPF (p less than 0.001). There was a significant reduction (p less than 0.002) in the erythrocyte count, the haematocrit and haemoglobin levels within 6-8 weeks of irradiation; this anaemia was characterized as a normochromic normocytic anaemia. There were no marked changes in plasma renin levels as a result of renal irradiation. The pathogenesis of late radiation-induced damage to the kidney is discussed in the light of these findings.

Sensitivity of human squamous cell carcinoma of the larynx to fractionated radiotherapy.

Data obtained for the response of tumours from two multicentre clinical trials of the British Institute of Radiology have been combined and studied. Both trials involved patients with laryngopharyngeal carcinoma. There were 734 patients in the first trial, recruited between 1965 and 1975, and 611 patients in the second trial, recruited between 1975 and 1985. Observed survival and tumour-free rates for all patients are calculated. T-class and the nodal status of the patient at the start of the treatment were important factors in the determination of both observed survival and tumour-free rates. Overall treatment time was an important factor in determining the recurrence of tumour. The longer the overall treatment time the greater was the chance of tumour recurrence. The linear-quadratic (LQ) model was used in the analysis of the tumour recurrence data for a large group of patients with laryngeal tumours without nodal involvement. A small alpha/beta ratio of 0.94 Gy was obtained for T3 tumours while that of T2 tumours was negative, -10.5 Gy. The value for T1 tumours was higher at 23 Gy. However, use of the LQ model with a time component increased the alpha/beta ratios to 26.0 +/- 27.20 Gy, 18.0 +/- 12.33 Gy and 13.38 +/- 5.40 Gy for T1, T2 and T3 tumours, respectively. The time component, the gamma/alpha ratios, for these tumours were 0.15 +/- 0.27 Gy/day, 0.81 +/- 0.18 Gy/day and 0.76 +/- 0.15 Gy/day, respectively.

Modification of radiation-induced acute oral mucositis in the rat.

Purpose: A new non‐toxic drug (compound A) consisting of curcumin, α‐tocopherol and sunflower oil was developed and its efficacy tested in the treatment of radiation‐induced oral mucositis in the rat. Material and methods: Mature (12 weeks old, 200–225g) female Sprague–Dawley rats were used. While under general anaesthesia, the tongues of the animals were slightly extended outside and a region of the underside of the tongue was irradiated in‐situ with single doses of 2.27 MeV β‐rays from a 5‐mm diameter 90Sr/90Y plaque. The dose‐rate of the source was about 10 Gy min−1 at the surface of the mucus membrane. Irradiations and subsequent assessment of the lesion were carried out under general anaesthesia maintained by a 1.5% halothane/oxygen mixture. Six groups of animals were irradiated with single doses of 13.5, 15.0, 16.5 or 18 Gy. One subgroup (radiation only) received no further treatment, while the other five groups received 0.5 ml day−1 of either compound A, sunflower oil, α‐tocopherol, curcumin or water containing 10% ethanol by oral gavage until the end of experiments. Mucosal ulceration (erosion of mucosal epithelium) was considered as an end‐point. From the day after irradiation until any acute radiation‐induced oral mucosal lesion had healed, the tongues of the animals were assessed daily for the presence of radiation‐induced mucositis (mucosal ulceration). Quantal data for the incidence of radiation‐induced mucositis were analysed using logit analysis and a dose‐modification factor was obtained. Results: There was a modest increase in ED50, the dose expected to cause mucositis in 50% of the animals after both α‐tocopherol and sunflower oil were administered. This resulted in dose‐modification factors of 1.05. While curcumin treatment resulted in a dose‐modification factor of 1.09. Compound A significantly reduced the incidence of radiation‐induced mucositis with a statistically significant dose‐modification factor of 1.2±0.1. Conclusions: Curcumin and other components of compound A appeared to be effective in the prevention of radiation‐induced oral mucositis. However, the overall effect observed with the combination drug (compound A) appeared greater than additive.

Normal tissue reactions in the British Institute of Radiology Study of 3 fractions per week versus 5 fractions per week in the treatment of carcinoma of the laryngo-pharynx by radiotherapy

The radiobiological data obtained from a multicentre clinical trial of the British Institute of Radiology, which compared the treatment of carcinoma of the laryngo-pharynx by 3 fractions per week (3F/wk) with 5 fractions per week (5F/wk) radiotherapy, have been studied. The trial involved an intake of 734 patients between 1966 and 1975. The number of fractions, overall treatment time and total doses used by different treatment centres ranges from 9 to 40 fractions, 18 to 70 days and 3880 to 7800 cGy, respectively. An 11-13% reduction in the total radiation dose was applied for treatments with 3F/wk as compared with 5F/wk in centres treating over 6 weeks and 3 weeks, respectively. All patients were followed for 10 years from the start of treatment. Different types of early and late normal-tissue reactions were investigated, ranging from a low percentage incidence of perichondritis to 95% for slight early reactions. Greater than 80% of the late normal-tissue reactions seen were observed within the first year after the start of treatment, and 96% were observed within the first 5 years. There was no statistically significant difference in the normal-tissue event-free rates between the 3F/wk and 5F/wk treatment groups. This finding did not differ when different major treatment centres were studied separately. For a number of end-points, alpha/beta ratios and N- and T-exponents of a modified nominal standard dose (NSD) formula have been calculated.

The predictive value of tumor classification compared with results of the british institute of radiology fractionation trial in the treatment of laryngopharyngeal carcinoma

Data from a clinical trial involving 734 patients have shown the value and the deficiencies of the current Union Internationale Contre le Cancers tumor, node, and metastasis classification system for prognostic purposes. The tumor‐category classification provides a good discriminant for both nodal involvement and survival; however, the previous node classification system only discriminated between node‐negative and node‐positive patients, as nodal fixity was not found to be a discriminator. The current anatomical site classification is ambiguous for some laryngeal and pharyngeal subsites, and modifications to the present system based on prognostic values are proposed. A difference in patient age between tumor categories has been shown, and various differences in incidence and survival data for the sexes have been demonstrated. Differences in observed and expected survival rates are related to continued late deaths from tumor. Multivariate analyses have shown that stage grouping is the most powerful prognostic discriminator, followed by anatomical site and age.

Residual Radiation-induced Damage to the Kidney of the Pig as Assayed by Retreatment

The effect of re-irradiation on the previously irradiated kidney was studied in the Large White female pig. Both kidneys of 14-week-old pigs were initially irradiated with a single dose of 3-7 Gy of 250 kV X-rays. The individual kidney glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and the haematocrit (Hct) were serially measured up to 24 weeks after X-irradiation. Doses of 3 and 5 Gy of X-rays had little effect on the GFR. However, 7 Gy of X-rays caused a marked decline in the GFR up to 12 weeks after irradiation; the GFR then began to recover. A similar pattern of response was seen in the ERPF. In contrast, the Hct was reduced in all pigs 4 weeks after X-irradiation. The extent of the decline and subsequent recovery 24 weeks after irradiation appeared to be related to dose. Twenty-four weeks after X-irradiation both kidneys were re-irradiated with a single dose of 7.9 Gy of 60Co gamma-rays; both kidneys of four age-matched control pigs which had not previously received X-irradiation were similarly treated. Individual kidney GFR, ERPF and Hct were again serially measured up to 24 weeks after gamma-irradiation. Re-irradiation resulted in a significantly greater reduction in the GFR, ERPF and Hct compared with that seen after gamma-irradiation alone. Moreover, the severity of the reduction in the GFR and Hct observed after gamma-irradiation was related, in a dose-dependent manner, to the initial X-ray doses employed. These results indicate that the kidney fails to exhibit complete long-term recovery in function following irradiation. Re-irradiation of the kidney in patients should thus be viewed with extreme caution.

The relative biological effectiveness of fractionated doses of fast neutrons (42 MeVd→Be) for normal tissues in the pig. IV, Effects on renal function

The effects of fractionated doses of fast neutrons (42 MeVd----Be) on the radiation response of the pig kidney have been assessed and compared with those observed after X irradiation. Following X irradiation there was a marked increase in the total dose at which renal function was preserved with decreasing fraction size. The rate of this increase was dependent on the overall treatment time; for fractionated irradiation given over 18 or 39 days the exponents related to fraction number, N, were 0.36 +/- 0.03 and 0.48 +/- 0.003, respectively. In contrast, there was no significant change in the iso-effect dose for renal injury following fractionated irradiation with fast neutrons where there was also little effect of varying the overall treatment time. Analysing these data by means of the linear-quadratic (LQ) model, using both an Fe-plot and the Tucker test, gave alpha/beta ratios of 2.42 +/- 0.06 Gy and 2.99 +/- 0.16 Gy, respectively, for X-ray doses given in 18 days. For fractionated doses of X rays given in 39 days the alpha/beta ratios were 0.40 +/- 0.01 Gy and 0.47 +/- 0.02 Gy, respectively. The alpha/beta ratios for renal tissue following fast neutron irradiation obtained by the two methods were also similar, i.e. 15.00 +/- 0.60 Gy and 15.72 +/- 3.76 Gy, respectively. The pronounced fractionation effect seen with X irradiation, particularly for doses administered over 39 days as opposed to 18 days, coupled with the absence of any such effect with fast neutrons, resulted in a marked increase in relative biological effectiveness (RBE) with decreasing X-ray dose/fraction. The slopes of the resulting regression lines were -0.73 +/- 0.05 and -0.33 +/- 0.02, respectively. The lack of dose sparing associated with fractionation, or variation of the overall treatment time for fast neutron irradiation, suggests that doses administered to tumours adjacent to the kidney can be given as a few relatively large dose/fractions in a short overall treatment time without an increased risk of complications related to renal tissue. This may be of therapeutic advantage in the treatment of rapidly proliferating tumours where dose may be wasted using more conventional protracted fractionated irradiation schedules.

Nephropathy in the mature pig after the irradiation of a single kidney: A comparison with the immature pig

The right kidney of 11 mature 10-month-old Large White female pigs was irradiated with single doses of 9.8-14.0 Gy of 60Co gamma rays. Individual kidney glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured using 99mTc-DTPA and 131I-hippuran renography for periods up to 24 weeks after irradiation. Renal function was assessed either as a functional index, FI (FI = irradiated/unirradiated kidney function), or as the individual kidney GFR and ERPF. The radiation-induced changes after the irradiation of a single kidney (unilaterally irradiated--UI) of mature pigs were compared with those previously observed in 14-week-old immature pigs. Irradiation resulted in a dose-dependent reduction in the FI for both GFR and ERPF. However, these reductions were significantly less than those previously seen in immature pigs. Within 2 weeks of irradiation GFR increased in both the irradiated and the unirradiated kidneys in each animal, compared with unirradiated age-matched control kidneys. No marked changes in renal hemodynamics were seen in mature animals after a single dose of 9.8 Gy. This was in marked contrast to the pronounced reduction in the GFR and ERPF in the irradiated kidney previously observed in immature animals irradiated with an equivalent single dose of X rays. After higher doses, the irradiated kidney in mature pigs showed a dose-dependent reduction in GFR and ERPF. However, the extent of this reduction was significantly less than that seen in immature animals. There was no apparent difference in the response of the unirradiated kidneys in mature or immature pigs. The ED50 values, based on a probit fit to the data for the proportion of functional tests in which the irradiated kidney showed a greater than or equal to 50% reduction in GFR or ERPF, were higher in the mature animals; for example for ERPF the ED50 values were 11.76 +/- 0.28 Gy and 7.67 +/- 0.34 Gy for mature and immature animals, respectively. Thus, the UI kidney in mature pigs appears to be less radiosensitive than the UI kidney in immature animals.

Protocol for X-ray dosimetry in radiobiology.

Purpose : To harmonize X-ray dosimetry in radiobiology to allow a direct comparison of radiobiological studies performed at institutes cooperating within the framework of the European Late Effects Project Group (EULEP). Materials and methods : The 1985 EULEP protocol for X-ray dosimetry and exposure arrangements employed for studies of late somatic effects in mammals required serious revision, e.g. due to the replacement of calibration of dosemeters in terms of exposure by calibration in terms of air kerma free-in-air. An action group established by EULEP and the European Radiation Dosimetry Group (EURADOS) updated the 1985 protocol. Results : The new EULEP-EURADOS protocol for X-ray dosimetry in radiobiology including the code of practice for irradiation of small animals and related dosimetry. The present protocol includes the changes in calibration procedures and dosimetric concepts for irradiation with medium energy X-rays since 1985. Accuracy and precision are replaced by the concept of combined (standard) uncertainty. The revised supplements provide more detailed background information. New appendices contain definitions of general terms used for measurements and mathematical expressions of the relative variances. Conclusion : Adherence to the present protocol will result in improved dosimetry and facilitates the comparison of results of radiobiological experiments obtained at different institutes.