[Contamination of the food chain with caesium-137 and strontium-90 in Switzerland]

One task of the field physiology of nutrition is the monitoring of the quality of feedstuffs. Rations may consequently be prepared with unadulterated components. This review uses the example of contamination with the radionuclides caesium-137 und strontium-90 and shows how these two unwanted substances reach the end host via the food chain and how their untoward effects are expressed in animals and humans. The extent of the contamination with artificial radioactivity is followed with periodical measurements according to the program of the Division for Radiological Protection of the Swiss Federal Office of Public Health. The interpretation of the measurements and the directives of this division are designed to protect primarily human health, but also that of animals.

Improving patient-specific dosimetry for intravascular brachytherapy

PURPOSE

Accurate patient-specific dosimetry in intravascular brachytherapy (IVBT) is generally difficult due to the extremely high-dose gradient, complexity of treatment device, and patient-specific geometry (e.g., calcification, stent, curvature, movement of target). The purpose of this study is to analyze quantitatively and systematically the dose effects of calcification, stent, guidewire, and source curvature on clinical dosimetry in an IVBT procedure, and propose a method that can be used to assess these effects in routine clinical practice.

METHODS AND MATERIALS

Monte Carlo techniques were used to calculate 3-D dose distribution in both homogeneous and inhomogeneous media for three most commonly used IVBT sources: (90)Sr beta (Novoste), (192)Ir gamma (Cordis/Best), and (32)P beta (Guidant). Dosimetric perturbations in the presence of metallic stents, calcified plaques, metallic guide wires, and source curvature were studied for situations commonly encountered in the clinic. The importance of each of these perturbations and their practical influence on patient-specific dosimetry were analyzed. Factors (plaque, stent, guidewire, and curvature) that may be used to correct/reduce these perturbations were introduced to prevent dosimetric cold spots during IVBT. Practical methods of using these correction factors are proposed.

RESULTS

Dose perturbations are significant due to the presence of source curvature, metallic stents, calcified plaques, and metallic guide wires, especially for beta sources. These perturbations can be as high as 30% under normal clinical conditions, although they can be much higher in extreme situations. Empirical relationships of plaque factor with the thickness of calcified plaque, stent factor with stent metallic surface area, guidewire with guidewire thickness, and curvature factor with the bending angle are derived. These relationships are found to be useful in improving clinical dose accuracy in IVBT treatment planning or dose evaluation after treatment.

CONCLUSIONS

Significant dose perturbations due to the presence of source curvature, metallic stents, calcified plaques, and guide wires have been found in IVBT for in-stent restenosis. Because it has been reported that, with the current prescriptions for IVBT, higher doses consistently improve treatment outcomes, the empirical method derived from this work can be used to assess cold spots dosimetrically, thus improving patient-specific dosimetry for IVBT.

Difficulty in dislodging in vivo fixed radiostrontium

Many trials based on the basic phenomena of isotopic dilution, adsorption, ion exchange, chelation, etc., have been attempted for the decorporation of radiostrontium, particularly Sr, after its entry in the in vivo system. We have recently demonstrated a non-isotopic carrier effect of some common calcium salts (calcium = 9 mg mL) to reduce the whole body retention of radiostrontium, if administered within 2 h after radiostrontium exposure and furthermore once daily, in rats, supplemented with calcium fortified diet. However, 25-30% of radiostrontium (compared to 50-60% in untreated animals) was still found to be retained in the animal even after 2 wk of treatment. Trial of some simple interventional measures, which would not adversely affect the animal metabolism, like pyrophosphate and magnesium sulfate, sodium citrate, chitin (a bio-absorbent), crown ether (a metal-chelator), and ammonium chloride, was therefore attempted to dislodge this remaining radiostrontium by switching over these animals to normal diet and subjecting them to different lines of treatment with these simple interventions through diet and drinking water separately for a further 4 wk. However, this remaining portion of radiostrontium is fixed in the bone and is difficult to dislodge.

Increased dosage during intracoronary irradiation due to overlapped source stepping shows no long-term adverse changes in vessel morphology

PURPOSE

The purpose of this analysis was to evaluate if overdosage during intracoronary irradiation due to overlapped source stepping may result in long-term morphologic changes in vessel anatomy.

METHODS

Baseline angiograms of patients with in-stent restenosis undergoing coronary reintervention followed by intracoronary irradiation with source stepping were analyzed. Overlapping was considered present for the segment with overlapped reference isodose length (RIL) (RIL = segment with > or = 90% of reference dose at 1 mm vessel wall depth). Baseline and 6-months follow-up volumetric intravascular ultrasound (IVUS) analysis were performed for the overlapped segment and for proximal and distal segments of equal length.

RESULTS

Overlapping was found in six patients (three patients: (32)P treatment; three patients: (90)Sr/Y treatment); final analysis was performed in four patients. Comparison of the baseline and follow-up IVUS volumetric parameters revealed no significant change in lumen or vessel volumes at segments of overlaps in comparison to proximal and distal reference segments.

CONCLUSION

Increased dosage due to overlapping during source stepping is not associated with morphologic changes in vessel anatomy at follow-up.

Radiotoxicity on bone marrow after 89Sr therapy radiosensitized by nicotinamide and carbogen in mice

OBJECTIVE

To investigate the radiotoxicity to bone marrow after 89Sr therapy radiosensitized by nicotinamide and carbogen.

METHODS

Chinese Kunming, NIH, BALB/c and F1 mice were divided into five groups: negative control (saline), positive control (89Sr), 89Sr+nicotinamide, 89Sr+carbogen and 89Sr+nicotinamide+carbogen. 89SrCl containing activities of 7400 kBq (200 microCi) in 200 microl of saline was administrated by injection into the tail vein. An equal volume of saline only was given to the negative control group. Chinese Kunming and NIH mice were killed on days 1, 2, 3, 4, 6, 8, 15, 20, 30, 60 and 90 after injection. BALB/c and F1 mice were killed on days 60 and 90. Femoral marrow reticulocytes were separated for assay of micronuclei.

RESULTS

The average frequency of the reticulocytes is shown in a dual-peak curve after injection. The first maximum frequency occurred between the second and the fourth days, and the second between the tenth and the 14th days. A significant statistical difference in frequency was found between the negative and the positive control groups (P<0.001, F=15.517), while no difference was found among the 89Sr+nicotinamide+carbogen, 89Sr, 89Sr+nicotinamide and 89Sr+carbogen groups (P>0.05, F=0.717) and among the NIH groups, 89Sr, 89Sr+nicotinamide, 89Sr+carbogen and 89Sr+nicotinamide+carbogen (P>0.05, F=1.734). There is also no significant difference in the frequency of reticulocytes between Chinese Kunming, NIH, BALB/c and F1 mice (P>0.05). Although the intervention of the radiosensitizer accelerated the occurrence of micronuclei in reticulocytes, there was no significant statistical difference between the group with radiosensitizer and the groups without it.

CONCLUSIONS

The administration of radiosensitizer did not aggravate the toxicity on bone marrow.

Uncertainties in dose coefficients from ingestion of 131I, 137Cs, and 90Sr

Quantification of uncertainties in doses from intakes of radionuclides is important in risk assessments and epidemiologic studies of individuals exposed to radiation. In this study, the uncertainties in the doses per unit intake (i.e., dose coefficients) for ingestion of 131I, 137Cs, and 90Sr by healthy individuals have been determined. Age-dependent thyroid dose coefficients were derived for 131I. The analysis for 131I uses recent measurements of thyroid volume obtained by ultrasonography, which indicate a thyroid mass lower than that previously obtained using autopsy measurements. The coefficients for 137Cs are determined using the relationship between the biological half-lives and the amount of potassium in the human body. The most recent International Commission on Radiological Protection biokinetic model was employed to determine the uncertainties for 90Sr. For 137Cs and 90Sr, the dose coefficients represent exposure in adulthood and they were determined for all organs of radiological importance. The uncertainty in the estimated dose coefficients represent state of knowledge estimates for a reference individual, and they are described by lognormal distributions with a specified geometric mean (GM) and geometric standard deviation (GSD). The estimated geometric means vary only slightly from the dose coefficients reported by ICRP publications. The largest uncertainty is observed in the dose coefficients for bone surface (GSD = 2.6), and red bone marrow (GSD = 2.4) in the case of ingestion of 90Sr. For most other organs, the uncertainty in the 90Sr dose coefficients is characterized by a GSD of 1.8 (or less for some organs). For 131I, the uncertainty in the thyroid dose coefficients is well represented by a GSD of 1.7 for both sexes and all ages other than infants for whom a GSD of 1.8 is more appropriate. The lowest uncertainties are obtained for the dose coefficients from ingestion of 137Cs (GSD = 1.24 for males; 1.4 for females). A dominant source of uncertainty in the ingestion dose coefficients is the variation of the biokinetic parameters. For 131I, the largest contribution to the uncertainty comes from the variation in the thyroid mass, but the contribution of the biokinetic parameters is comparable. The biokinetic parameters with the largest contribution to the uncertainty are (a) the fractional uptake from blood to thyroid in the case of ingestion of 131I, (b) the absorbed fraction from the gastrointestinal tract (f1) in the case of 90Sr, and (c) the amount of potassium in the body for 137Cs. The contribution to the uncertainty of the absorbed fraction (which accounts for the fraction of energy deposited in the target organ) is the smallest contributor to the uncertainty in the dose coefficients for most organs. To reduce the uncertainty in the dose estimated for a real individual, one should determine the above-mentioned parameters for the specified individual rather than to rely on assumptions for a reference individual.

Treatment of bifurcation in-stent restenotic lesions with beta radiation using strontium 90 and sequential positioning pullback technique: procedural details and clinical outcomes

BACKGROUND

In-stent restenotic lesions have been problematic for many patients with the need for multiple repeat percutaneous coronary interventions (PCI). The need for repeat PCI has been significantly reduced in patients since the advent of vascular brachytherapy. In-stent restenosis resulting in bifurcation presents even more of a challenge. The use of radiation therapy for the treatment of this kind of lesion has not yet been reported. The purpose of this paper is to present five cases of radiation therapy in bifurcation in-stent restenotic lesions using the intraluminal beta radiation catheter delivery system (Beta-Cath System, Novoste Corporation, Norcross, Georgia).

METHODS

We reviewed the database of patients enrolled in our Compassionate Use Registry between August 1999 and April 2002. The data is reported for 5 patients who received radiation in both branches of bifurcation lesions with the Beta-Cath catheter system.

RESULTS

The mean diameter of the vessels was 3.1 mm 0.5 mm. The dose administered was from 18.3 to 23 Gy, with an overlap of 3.3 to 10.3 mm; the hinge angle between the branches went from 43.3 to 65.4 . Angiographic follow-up was obtained at 6 months in 4 patients, with a single patient showing a focal (< 5 mm) edge lesion treated by balloon angioplasty (TVR no TLR). No aneurysms or zones of ectasia were noted.

CONCLUSION

Beta radiation with the Beta-Cath catheter system appears to be safe, secure and clinically useful in in-stent restenotic bifurcation lesions.

Effects of low chronic doses of ionizing radiation on antioxidant enzymes and G6PDH activities in Stipa capillata (Poaceae)

Stipa capillata (Poaceae) seeds were harvested from a control area (displaying a gamma dose rate of 0.23 micro Sv h(-1)) (C plants) and from two contaminated areas (5.4 and 25 micro Sv h(-1)) on the Semipalatinsk nuclear test site (SNTS) in Kazakhstan. The plants were grown for 124 d in a greenhouse under controlled conditions and exposed to three different treatments: (0) control; (E) external gamma irradiation delivered by a sealed 137Cs source with a dose rate of 66 micro Sv h(-1); (E+I) E treatment combined with internal beta irradiation due to contamination by 134Cs and 85Sr via root uptake from the soil. The root uptake led to a contamination of 100 Bq g(-1) for 85Sr and 5 Bq g(-1) for 134Cs (of plant dry weight) as measured at harvest. The activity of SOD, APX, GR, POD, CAT, G6PDH, and MDHAR enzymes was measured in leaves. Under (0) treatment, all enzymes showed similar activities, except POD, which had higher activity in plants originating from contaminated areas. Treatment (E) induced an enhancement of POD, CAT, GR, SOD, and G6PDH activities in plants originating from contaminated areas. Only control plants showed any stimulation of APX activity. Treatment (E+I) had no significant effect on APX, GR, CAT, and POD activities, but MDHAR activity was significantly reduced while SOD and G6PDH activities were significantly increased. The increase occurred in plants from all origins for SOD, with a greater magnitude as a function of their origin, and it occurred only in plants from the more contaminated populations for G6PDH. This suggests that exposure to a low dose rate of ionizing radiation for almost a half century in the original environment of Stipa has led to natural selection of the most adapted genotypes characterized by an efficient induction of anti-oxidant enzyme activities, especially SOD and G6PDH, involved in plant protection against reactive oxygen species.

Measured TG-60 dosimetric parameters of the Novoste Beta-Cath 90Sr/Y source trains for intravascular brachytherapy

Measurements were performed on the 30, 40 and 60-mm 90Sr/Y beta-emitter source trains used in the Novoste Beta-Cath system to determine the dosimetric characteristics of the sources at millimeter distances and provide the necessary TG-60 dosimetry parameters for mapping the dose distributions. These measurements were carried out in a Solid Water phantom where MD-55-2 Gafchromic films were placed in direct contact with a 5 French (F) catheter used for the 30 and 60-mm source trains and a 3.5 F catheter used for a thinner 40-mm source train. The dosimetric analysis was performed according to the AAPM TG-60 formalism. For the 30-mm source train, data were collected with the source axis at distances of 0.41 and 1.19 mm from the film surface, respectively, in order to investigate possible dosimetric effects due to the intrinsic off centering of the source train lumen within the 5 F catheter. Absolute dose rates at 2 mm were determined by calibrating the radiochromic film in a high energy electron beam from a radiotherapy accelerator. The dose rates at a radial distance of 2 mm were found to be within 10% of the values provided by Novoste. Radial dose functions from this study were in good agreement (< or = 10%) with a 30-mm, 90Sr/Y source train dose data generated from C. G. Soares et al. 90Sr/Y single seed data. However, larger differences were observed at distances shorter than 1 mm when compared to radial dose functions from the Novoste Monte Carlo data.

[Evaluation of the effect of dose rate and dose absorption on the long-term radiation consequences in rats chronically taking in 90Sr]

The effects of exposure to 90Sr which was given with food with daily doses 18.5 kBq per animal for 1-12 months, 37 kBq per animal for 1-10 months, 74 kBq per animal for 1-8 months and 148 kBq per animal for 1-6 months on mortality patterns in unimbred white rats were investigated. Hazard models were used to evaluate dose rate and accumulated dose influence on radiation-related trends in mortality. The time-dependent risk of death from all causes and from osteosarcomas depended on the dose rate. The risk of death from causes other than osteosarcoma depended on the dose rate and the accumulated dose. To predict time-dependent risk of death it was better to use the least time to calculate the dose rate--1 day.

Uptake of cesium-137 and strontium-90 from contaminated soil by three plant species; application to phytoremediation

A field test was conducted to determine the ability of three plant species to extract 137Cs and 90Sr from contaminated soil. Redroot pigweed (Amaranthus retroflexus L.), Indian mustard [Brassica juncea (L.) Czern.], and tepary bean (Phaseolus acutifolius A. Gray) were planted in a series of spatially randomized cells in soil that was contaminated in the 1950s and 1960s. We examined the potential for phytoextraction of 90Sr and 137Cs by these three species. Concentration ratios (CR) for 137Cs for redroot pigweed, Indian mustard, and tepary bean were 2.58, 0.46, and 0.17, respectively. For 90Sr they were substantially higher: 6.5, 8.2, and 15.2, respectively. The greatest accumulation of both radionuclides was obtained with redroot pigweed, even though its CR for 90Sr was the lowest, because of its relatively large biomass. There was a linear relationship between the 137Cs concentration in plants and its concentration in soil only for redroot pigweed. Uptake of 90Sr exhibits no relationship to 90Sr concentrations in the soil. Estimates of time required for removal of 50% of the two contaminants, assuming two crops of redroot pigweed per year, are 7 yr for 90Sr and 18 yr for 137Cs.

Topical application of beta-radiation to reduce intimal hyperplasia after carotid artery balloon injury in rabbit. A possible application for brachytherapy in vascular surgery

PURPOSE

Endovascular brachytherapy for the prevention of intimal hyperplasia (IH) and restenosis after balloon/stent angioplasty has proven effective both in animal preparations and clinical trials. A variety of beta-emitting isotopes and catheter-based devices have been developed for the delivery of low-dose radiation in clinical coronary and peripheral trials. No platform, however, has yet been developed for brachytherapy in concert with vascular surgical operations. The purpose of this study was to evaluate the vascular histopathologic response following balloon injury to rabbit carotid arteries with and without topically applied low-dose beta-radiation.

METHODS

The beta-emitting isotope strontium-90 (Sr-90) was conjugated onto the matrix of polypropylene (PLYP) mesh. Rabbit carotid arteries were balloon-injured with a #2 embolectomy catheter. Six carotid arteries were wrapped with nonradioactive PLYP mesh (controls) and Sr-90 ( approximately 90 microCi) PLYP mesh in order to deliver low-dose radiation to the vessel wall from the external (adventitial) surface. Tissue was harvested at 6 weeks and processed for histologic examination.

RESULTS

There was consistent blockade of fibrocellular neointima formation with virtually no neointima present in all treated segments, compared to moderate neointima formation in controls. Medial thinning and smooth muscle cell (SMC) necrosis were also associated with topical brachytherapy.

CONCLUSION

beta-Radiation applied by an externally wrapped PLYP mesh labeled with Sr-90 markedly suppressed neointima formation in an animal vascular surgical injury model. Further studies, however, are necessary to determine a suitable isotope and dosage for clinical application.

A mathematical model for calculation of 90Sr absorbed dose in dental tissues: elaboration and comparison to EPR measurements

A mathematical model for calculation of the 90Sr absorbed doses in dental tissues is presented. The results of the Monte-Carlo calculations are compared to the data obtained by EPR measurements of dental tissues. Radiometric measurements of the 90Sr concentrations. TLD and EPR dosimetry investigations were performed in animal (dog) study. The importance of the irregular 90Sr distribution in the dentine for absorbed dose formation has been shown. The dominant dose formation factors (main source-tissues) were identified for the crown dentine and enamel. The model has shown agreement with experimental data which allows to determine further directions of the human tooth model development.

A multicentre observational study of radionuclide therapy in patients with painful bone metastases of prostate cancer

A multicentre observational study was conducted by the Italian Association of Nuclear Medicine between 1996 and 1998. Twenty-nine Nuclear Medicine Departments participated. The aims of the study were to systematically evaluate the efficacy, toxicity and repeatability of radionuclide therapy of painful bone metastases (RTBM) in a large number of patients and to assess its incidence in patients with prostate cancer. Out of 818 treatments performed with a single i.v. dose of 148 MBq of strontium-89 chloride or 1,295 MBq of rhenium-186 hydroxyethylidene diphosphonate (HEDP), 610 could be evaluated (527 with 89Sr and 83 with 186Re-HEDP). Eighty-one patients received multiple (up to five) RTBM. The total number of retreatments was 100. Patients were followed up for a period of 3-24 months. Results, assessed according to pain relief and consumption of analgesic drugs, were expressed at four levels: 1, no response; 2, mild response; 3, good response; 4, excellent response. Responses were: level 1 in 19%, level 2 in 21.3%, level 3 in 33.3% and level 4 in 26.4% of cases. Retreatments showed significantly (P<0.01) worse responses (48% levels 3+4), in comparison to first RTBM. Duration of palliation was 5.0+/-3.5 months, and was longer in cases of excellent response, in first RTBM, in patients with limited metastases and when 89Sr was used. Better responses were found in cases of limited skeletal disease, under good clinical conditions, when life expectancy exceeded 3 months, and in radiologically osteoblastic or mixed bone lesions. The only statistically significant predictive factor was life expectancy (P<0.001). Flare phenomenon (14.1% of cases) did not correlate with the response. Haematological toxicity (mild to moderate in most cases) mainly affected platelets, and was observed in 25.5% of cases overall and in 38.9% of retreatments. RTBM did not seem to prolong life, though in some cases scintigraphic regression of bone metastases was observed. The two radiopharmaceuticals did not show any statistically significant differences in palliative efficacy and toxicity, either in first RTBM or in retreatments.

ESR dosimetry of 89Sr and 153Sm in bone

The radiation absorbed dose in the rabbit bone delivered by 153Sm-EDTMP (samarium ethylenediaminetetra methylene diphosphonic acid) and 89SRCl2 (strontium chloride) was measured by means of electron spin resonance (ESR). These radioisotopes are used in systemic radiotherapy for palliation of painful bone metastases. The knowledge of the dose is important in order to avoid side effects to the bone marrow. The ESR radiation dose signal was calibrated by the additive dose method using cobalt-60 gamma rays. For 153Sm-EDTMP, the bone doses in three rabbits were (4 +/- 2), (5 +/- 1) and (5 +/- 2) cGy kg/MBq. For 89SrCl2, a dose of (2 +/- 1) cGy kg/MBq was found in one rabbit.

[Late stent thrombosis after intracoronary brachytherapy. A case report and review of the literature]

Intracoronary irradiation is currently the most promising approach to reduce restenosis after percutaneous transluminal coronary angioplasty. Meanwhile numerous data are available concerning efficacy and safety of this novel method. These data confirm the results of preclinical studies that reported a dramatic reduction of neo-intima proliferation and negative remodeling. However, the number of reports on an elevated incidence of late stent thrombosis (> 30 days post intervention) are increasing. It is commonly suggested that the delayed neo-intima formation within vascular stents is responsible for this new phenomenon. We report the case of a 48-year-old man who underwent coronary irradiation therapy after stent placement in a de-novo/restenotic lesion. Despite an explicit recommendation of a combined anti-aggregatory therapy consisting of ticlopidine and acetysalicylic acid for at least 6 months, ticlopidine was withdrawn after 4 weeks. Two weeks later, the patient was readmitted to an external hospital with an acute myocardial infarction and successfully treated with thrombolysis. The angiographic and intravascular control, which was conducted after another two weeks, showed absolutely no neointima formation within the implanted stent. Thus, a late thrombotic occlusion of the implanted stent appears most likely to be the cause underlying the myocardial infarction. This case underlines, together with other existing reports, the importance of a prolonged, combined anti-aggregatory therapy after stent placement and subsequent intracoronary irradiation.

[Evaluation of late radiation-induced changes in superficial microcirculation after acute beta-irradiation. II. Prognostic importance of cutaneous Doppler laser]

OBJECTIVE

The changes that occur in the tissular microcirculation after accidental acute irradiation account for some of the early effects of such irradiation, especially at the cutaneous level. The prognostic importance of the cutaneous laser doppler was tested in an experimental model of acute beta-irradiation.

METHODS

Ten pigs were given beta-irradiation with a high single localized dose of 90Sr/90Y (32 or 64 Gy, 7 mg/cm2) delivered to the flank, and were evaluated 2, 7, 14, 21 and 28 days thereafter. Each individual was its own control. The local microcirculation was measured in the resting state and during thermal stimulation at 42 degrees C, using a Periflux cutaneous Doppler laser with p413 probes. Three periods of six minutes each were continuously recorded: period 1 (P1) represented basal resting cutaneous perfusion, with the slope p corresponding to the increase in perfusion when two minutes of thermal stimulation at 42 degrees C began; P2 to plateau perfusion during this stimulation; and P3 to perfusion on the return to equilibrium.

RESULTS

After acute beta-irradiation in the pig, all the cutaneous microcirculation parameters measured (P1, p, P2 and P3) had risen at day 2 in the irradiated area by a factor of 2 to 4, depending on the dose (p < 0.001), compared to the adjacent control area. On the other hand, as from day 7, the resting and the stimulated microcirculation varied little, except for a reduction of the slope p by a factor of 2 (p < 0.05) after the strongest radiation dose.

CONCLUSION

After acute irradiation, the increase in the resting cutaneous microcirculation may correspond to immediate but transitory capillary vasodilatation that accompanies the initial erythema in accidental irradiation. The absence of vascular response to thermal stimulation seems to be a good means of reaching an early diagnosis of delayed cutaneous radiation necrosis.

Treatment of bone metastases of prostate cancer with strontium-89 chloride: efficacy in relation to the degree of bone involvement

This retrospective study evaluated the toxicity and efficacy of strontium-89 chloride (Metastron, Amersham) in 94 patients with painful bone metastases of prostate cancer (117 injections of 150 MBq) and compared the efficacy of treatment in patients with moderate and extensive bone involvement. The predictive value of flare response with regard to analgesic response was also studied. High-grade leukothrombopenias were observed after only 5% of injections. An improvement in quality of life was obtained in 65% of cases, a decrease in pain in 78% (31% complete response) and a reduction of analgesics in 60%. Efficacy was significantly better for pain decrease (P=0.005) and reduction of analgesics (P=0.018), and response was significantly longer (P<0.0035) in patients with moderate than in patients with extensive bone involvement. The flare response observed in 23% of cases was not predictive of pain response (P=0.919) or reduction of analgesics (P=0.353). A second dose prolonged analgesia in three-quarters of cases without any apparent increase in toxicity. These results confirm the benefit of 89Sr chloride for the treatment of metastatic bone pain and suggest that internal radiotherapy should be started earlier. A bone scan could be proposed at the time of hormonal escape resulting in bone pain, and internal radiotherapy could be initiated when several metastatic foci exist, even if only one is painful. In this way, pain-free follow-up could be prolonged, and the transition to other therapeutic approaches, particularly opioids, delayed.

Does body size contribute to sensitivity of bone tumor induction by radionuclide exposure?

Investigation of a possible increase in sensitivity to occurrence of radionuclide-induced skeletal malignancy with increasing body size was analyzed among 358 beagles injected as young adults with either 226Ra or monomeric 239Pu and maintained for their lifespans. Corresponding analyses were performed for about 240 other beagles injected as young adults with 90Sr, 228Ra, or 228Th. Body masses at the time of injection ranged between about 5.6 and 16 kg. Logistic regression analysis using body mass and cumulative skeletal radiation dose as the independent variables indicated that there could not be established a dependency of tumor occurrence upon body mass, although skeletal dose was found to be significantly correlated with occurrence of bone cancer. Regression analysis indicated that for any dosage group there could not be established a correlation between body mass and skeletal dose. Each dosage group having similar injected kBq kg(-1) for each nuclide was divided into 2 subgroups of equal size, one containing the less massive dogs and the other containing the more massive dogs. These subgroups within a roughly uniform value of skeletal dose-rate were compared by Fisher's Exact Test, and the less massive subgroups were combined within each nuclide for an additional, separate analysis against the combined more massive subgroups using the same method. In only one instance (the dosage group given 3607 kBq 90Sr kg(-1)) was there indicated a substantially greater tumor occurrence among dogs in the more massive subgroup (p = 0.061). However, for the group given 0.382 kBq 239Pu kg(-1) there was indicated a significant difference between subgroups, but the effect was exactly opposite to that found for the highest level 90Sr dogs in that the less massive subgroup had a higher relative tumor occurrence than the most massive (p = 0.042). For all groups with a p-value < 0.10, a possible correlation was investigated between survival and body mass at injection (since bone tumor occurrence might be a function of longevity), but a significant relationship could not be determined. No significant differences could be established between the combined more massive and the combined less massive subgroups for any radionuclide. We conclude that, for the conditions in our experiment, relative size within a species does not contribute importantly to the sensitivity (lifetime occurrence) for induction of skeletal malignancy.

[The effect of internal exposure to 90Sr on hematopoietic stem cells in CBA mice]

After acute intake of 90Sr the changes of d-9 CFUs number in mice (CBA) bone marrow, spleen and peripheral blood were investigated. The obtained results indicated similar quantitative changes in bone marrow and spleen CFUs on exposure to the 90Sr when radiation doses did not cause the decrease in life-time (1.11 kBq/g). Sarcomogeneous doses of 90Sr (29.6 kBq/g) resulted in drastic changes of hemopoietic system: spleen haematopoiesis activation and suppression of bone marrow functions. On the first day after 90Sr injection (29.6 kBq/g) the increase in number of peripheral blood CFUs (circulating pool) was observed.

Calibration of strontium-90 eye applicator using a strontium external beam standard

Four techniques for measuring the dose rate from Sr-90 concave eye plaques are presented. The techniques involve calibrating a concave eye plaque against a Sr-90 teletherapy unit using X-Omat film, radiochromic film, black LiF TLD discs and LiF chips. The mean dose rate predicted by these dosimeters is 7.5 cGy s(-1). The dose rate quoted by the manufacturer is 33% lower than this value, which is consistent with discrepancies reported by other authors. Calibration against a 6 MV linear accelerator was also carried out using each of the above dosimetric devices, and appropriate sensitivity correction factors have been presented.

Relative efficacy of 32P and 89Sr in palliation in skeletal metastases

32p and 89Sr have been shown to produce significant pain relief in patients with skeletal metastases from advanced cancer. Clinically significant pancytopenia has not been reported in doses up to 12 mCi (444 MBq) of either radionuclide. To date, no reports comparing the relative efficacy and toxicity of the two radionuclides in comparable patient populations have been available. Although a cure has not been reported, both treatments have achieved substantial pain relief. However, several studies have used semiquantitative measures such as "slight," "fair," "partial" and "dramatic" responses, which lend themselves to subjective bias. This report examines the responses to treatment with 32P or 89Sr by attempting a quantification of pain relief and quality of life using the patients as their own controls and compares toxicity in terms of hematological parameters.

METHODS

Thirty-one patients with skeletal metastases were treated for pain relief with either 32P (16 patients) or 89Sr (15 patients). Inclusion criteria were pain from bone scan-positive sites above a subjective score of 5 of 10 despite analgesic therapy with narcotic or non-narcotic medication, limitation of movement related to the performance of routine daily activity and a predicted life expectancy of at least 4 mo. The patients had not had chemotherapy or radiotherapy during the previous 6 wk and had normal serum creatinine, white cell and platelet counts. 32P was given orally as a 12 mCi dose, and 89Sr was given intravenously as a 4 mCi (148 MBq) dose. The patients were monitored for 4 mo.

RESULTS

Complete absence of pain was seen in 7 of 16 patients who were given 32P and in 7 of 15 patients who were given 89Sr. Pain scores fell by at least 50% of the pretreatment score in 14 of 16 patients who were given 32P and 14 of 15 patients who were given 89Sr. Mean duration of pain relief was 9.6 wk with 32P and 10 wk with 89Sr. Analgesic scores fell along with the drop in pain scores. A fall in total white cell, absolute granulocyte and platelet counts occurred in all patients. Subnormal values of white cells and platelets were seen in 5 and 7 patients, respectively, with 32P, and in 0 and 4 patients, respectively, after 89Sr therapy. The decrease in platelet count (but not absolute granulocyte count) was statistically significant when 32P patients were compared with 89Sr patients. However, in no instance did the fall in blood counts require treatment. Absolute granulocyte counts did not fall below 1000 in any patient. There was no significant difference between the two treatments in terms of either efficacy or toxicity.

CONCLUSION

No justification has been found in this study for the recommendation of 89Sr over the considerably less expensive oral 32P for the palliation of skeletal pain from metastases of advanced cancer.

Strontium-89 (89Sr) analgesia for rare thymic carcinoid tumor with bony metastases

The authors report the cases of two patients in whom strontium-89 (89Sr) was used to relieve diffuse metastatic bone pain. The type of cancer involved, thymic carcinoid tumor, is itself rare and the risk of its metastasizing to the bone is very low. Both patients showed a measure of response to treatment, suggesting that this analgesic method has value for some patients. The marked benefit of one patient for a total of 9 months was attributable to two 89Sr injections, whereas the other patient improved for only 5 weeks after one injection.

Strontium-89 chloride in the treatment of bone metastases from breast cancer

Sixty-four patients with painful metastatic breast cancer in bone were treated with 2 MBq/kg of strontium-89 chloride as a single intravenous injection. Patients were followed with records of medication, hematology parameters, serial bone and Sr-89 bremsstrahlung images and with a point pain score scale (10-0). The response was assessed during a 6-month period of follow-up. Fifty-two of 64 patients (81%) showed at least a moderate improvement. Eighteen out of the 52 responders showed a dramatic decrease in bone pain (35%), 21 (40%) presented a satisfactory response and in 13 cases (25%) the response was moderate. Only 12 patients (19%) from the whole group did not feel any improvement on pain palliation. A statistically significant decrease of pretreatment levels of platelets and leukocyte counts was observed after 4-6 weeks of therapy in 50 (70%) patients. Although most patients showed no change in their bone scans after 3 months of treatment, an obvious improvement was observed in 3 of them. Furthermore no additional painful metastases on their bone scintigraphic images were observed. The selective strontium-89 local uptake in metastatic sites was also confirmed directly by bremsstrahlung scans which were absolutely comparable to the respective 99mTc bone scans. Precautions have been taken against Sr-89 contamination from the patients' blood or excretions.