Radionuclide-targeted therapy for the management of metastatic bone pain

Strontium-89 is preferentially taken up at sites of increased bone mineral turnover, its uptake adjacent to malignant metastases being up to five times greater than for normal bone. Strontium-89 is also selectively retained in bone adjacent to metastatic sites. The initial therapeutic ratio is therefore good and increases with time. The pharmacokinetics of strontium-89 thus favor the objective of achieving a clinically effective beta radiation dose to tumor deposits while minimizing radiation exposure to healthy tissue. Clinical studies show that 150 MBq [corrected] strontium-89 can relieve bone pain in up to 80% of patients with prostatic metastases. Greater activities do not appear to increase this level of response. Once a response has been achieved, strontium-89 therapy can be repeated when pain recurs. Although hematologic toxicity at this dosage is low, strontium-89 should not be given to patients with evidence of significant bone marrow depression. With this precaution, no serious toxicity has been encountered when the agent is administered at the recommended doses.

Phase I/II study of iodine 131 metaiodobenzylguanidine in chemoresistant neuroblastoma: a United Kingdom Children's Cancer Study Group investigation

PURPOSE

The goal of this study was to evaluate the toxicity of iodine 131 metaiodobenzylguanidine (mIBG) in metastatic neuroblastoma.

PATIENTS AND METHODS

A multicenter phase I study of 131I mIBG has been undertaken by the United Kingdom Children's Cancer Study Group (UKCCSG) in children with advanced chemoresistant neuroblastoma. Activity prescription was based on a prescribed whole-body radiation dose, which was established for individual patients by performing an initial tracer investigation with 75 MBq of 131I mIBG. An activity was derived from this pharmacokinetic study that would deliver an initial whole-body-absorbed radiation dose of 1 Gy. Subsequent dose escalations were based on observed toxicity.

RESULTS

Twenty-five patients, aged 1 to 10 years, were treated with prescribed whole-body dose levels of 1.0 Gy (n = 2), 2.0 Gy (n = 13), and 2.5 Gy (n = 10). This necessitated administration of 2.4 to 12.1 GBq of activity. Hematologic, hepatic, kidney, and adrenal toxicity were observed, with bone marrow suppression being the principal dose-limiting toxicity. Bone marrow toxicity increased with prescribed whole-body-absorbed radiation dose, with 80% of patients developing grade 3 or 4 thrombocytopenia at a prescribed whole-body radiation dose of 2.5 Gy. Objective evidence of tumor response was seen in soft tissue (primary or nodal disease), bone, and bone marrow, with an overall response rate of 33% (partial response, n = 8; static disease, n = 9; progressive disease, n = 7).

CONCLUSIONS

This study has established an effective method of activity prescription that predicts subsequent toxicity, with the maximally tolerated dose being sufficient activity to deliver a whole-body-absorbed radiation dose of 2.5 Gy. The objective response rate is comparable to other single agents in chemoresistant neuroblastoma and suggests that 131I mIBG may be a useful method for targeting radiotherapy in metastatic neuroblastoma.

Dosimetry of iodine 131 metaiodobenzylguanidine for treatment of resistant neuroblastoma: results of a UK study

In 1987, the United Kingdom Children's Cancer Study Group (UKCCSG) set up a multi-centre study to investigate the toxicity of iodine 131 metaiodobenzylguanidine (mIBG) in the treatment of resistant neuroblastoma. Since December 1987, 25 children suffering from neuroblastoma have been treated with 131I-mIBG at six UK centres. All centres followed standardised physics and clinical protocols to provide consistent toxicity and dosimetry data. These protocols describe the methods employed for both the tracer study using 131I-mIBG and the subsequent therapy. Whole-body dosimetry calculations were performed on data from the tracer study. The activity administered for therapy was the amount predicted to deliver a predefined whole-body dose. Estimates of doses delivered to various organs during treatment are given in Table 1.

Distribution of bony metastases in prostatic carcinoma

Fifty-five prostate cancer and 55 breast cancer patients with positive bone scintigrams were studied. The pattern of spread in the axial skeleton and pelvis showed differences between the 2 groups. This difference was not related primarily to bone volume at the site of metastasis. The difference in distribution of bony metastases between breast and prostate is explained by our knowledge of Batson's vertebral venous plexus.

A gamma camera method to monitor the use of degradable starch microspheres in hepatic arterial chemotherapy

A gamma camera method to quantify the haemodynamic effects of degradable starch microspheres (DSM) in intra arterial hepatic therapy is described. Results are presented from ten patients with colorectal liver metastases. Intra hepatic arterio venous shunting was present in 1 patient prior to DSM and in 2 subjects after three 300 mg DSM fractions. DSM reduced the rate of flow of injectate to the lung in all cases. Conversely, an increased rate of flow of injectate to gut or spleen occurred with 300 mg fractions of DSM in 7/9 cases. Lower dose DSM fractions are indicated. At 2-3 min after DSM injection the mean fraction of the activity retained in the liver was 0.22. A DSM induced enhancement of tumour relative to normal tissue perfusion was obtained in four out of five tumour regions identified. All indices showed a wide variation between patients and between individual DSM doses, and the high incidence of extra hepatic shunting confirms the need for monitoring when using intra arterial microspheres.

Ventilation/perfusion mismatch in interstitial fibrosis

Regional pulmonary perfusion defects unmatched by ventilation loss, occurring in a patient with proven interstitial lung fibrosis, is reported. This condition is not a widely recognized cause of ventilation/perfusion mismatch.

Longitudinal assessment of glomerular filtration rate by gamma camera and portable external detector

Noninvasive isotope chelate methods to assess glomerular filtration rate (GFR) are less accurate than blood sampling. However, some measurement errors would be expected to be constant for an individual, and repeat estimations may be less variable. In 18 patients, estimates of GFR were obtained by 2 gamma camera techniques and a portable external detector at a mean interval of 1 year, to assess accuracy in predicting a change of GFR. Errors in these techniques were not significantly better than those predicted from two independent estimates. Most GFR measurement error for noninvasive methods appears to be random.

Measurement of glomerular filtration rate with a portable cadmium telluride detector

The plasma clearance rate constant of 99Tcm-DTPA was measured with a portable cadmium telluride detector over anterior chest wall and lateral leg sites to obtain an empirical estimate of glomerular filtration rate (GFR). Thirteen patients with a range of renal dysfunction were studied to compare the accuracy of the estimates over various time periods compared to GFR estimated from plasma sampling. The chest site was more accurate for GFR assessment over all time periods assessed up to 4 h following injection. The clearance rate constants obtained up to 1 h after injection from the chest site were not significantly less accurate then those from later time periods.

Measurement of glomerular filtration rate with 99mTc-DTPA: a comparison of gamma camera methods

A comparison has been made between three gamma camera methods for estimation of glomerular filtration rate (GFR) using 99mTc-DTPA in a group of 27 patients with widely different renal function. Plasma clearance of 99mTc-DTPA by multiple blood sampling was used as the reference. Percentage uptake of chelate in the bladder and kidneys at 20 min after injection gave the lowest standard error of 8.0 ml/min. Techniques using early uptake of isotope in the kidneys at 2 min after injection gave less accurate estimates. Correction for the vascular activity in the renal region of interest improved the results for the 2 min uptake technique. Gamma camera techniques provide rapid estimates of GFR which are less accurate than those obtained by plasma clearance of labelled chelate.

Does radiolabelled diphosphonate retention reflect bone metabolism in the elderly?

The 24-h whole-body retention of diphosphonates (WBR), a useful measure of bone metabolism in young subjects, was measured in 27 elderly subjects (19 from home and eight in-patients). WBR rose with increasing age (r = 0.55, P less than 0.01) and was negatively correlated with renal function (r = -0.60, P less than 0.01). In five subjects given vitamin D, WBR did not fall. The measurement of WBR in the elderly has to be assessed in the light of an accurate assessment of renal function and so is rarely clinically useful.

Radioiodinated iodobenzylguanidines for diagnosis and therapy

Radiolabelled meta-iodobenzylguanidine has been one of the most successful of recent radiopharmaceuticals. In the short period of five years it has been shown to have high diagnostic sensitivity and specificity for many tumours of neuroectodermal origin. Furthermore its excellent concentration in many malignant tumours of this type offers a novel alternative treatment to those available at present.

Unilateral pulmonary blood flow loss in a young patient

A case of total unilateral loss of pulmonary perfusion with almost normal ventilation, in a 21-year-old male patient is described, and the problem of interpretation in an asymptomatic patient is illustrated.

Vitamin B12 absorption after necrotizing enterocolitis

Resection of the terminal ileum for necrotizing enterocolitis is not uncommon in neonates requiring intensive care in the first weeks of life. They may therefore be at risk of vitamin B12 malabsorption, and later of vitamin B12 deficiency. A method of measuring B12 absorption is described and the results are given. This assessment should be part of the follow up for all these children.

A comparison between the use of a shadow shield whole body counter and an uncollimated gamma camera ain the assessment of the seven-day retention of SeHCAT

We have compared the 7-day retention of the radioisotope bile salt analogue SeHCAT (75Se-23-selena-25-homotaurocholate), by whole body counting and by uncollimated gamma camera measurement, in phantoms and in 25 patients with inflammatory bowel disease. The results correlate with a linear correlation coefficient of 0.96. An uncollimated gamma camera can be used to assess bile acid malabsorption when a whole body radioactivity monitor is not available.

Disseminated malignant phaeochromocytoma: localisation with iodine-131-labelled meta-iodobenzylguanidine

Meta-iodobenzylguanidine, a guanethidine analogue, is a newly synthesised substance capable of imaging the adrenal medulla. In a woman in whom phaeochromocytoma has been diagnosed iodine-131-labelled metaiodobenzylguanidine was given intravenously; gamma-camera images showed bilateral adrenal tumours and uptake corresponding to bone and liver metastases. 131I-meta-iodobenzylguanidine is effective in localising phaeochromocytomas, and the technique is safe, specific, and non-invasive.

The comparison of 8-hydroxyquinoline, tropolone, and acetylacetone as mediators in the labelling of polymorphonuclear leucocytes with indium-111: a functional study

Tropolone forms a lipophilic complex with indium-111 which is capable of mediating the labelling of polymorphonuclear leucocytes (PMNs) by this isotope; labelling efficiencies are comparable with the best achieved using 8-hydroxyquinoline and acetylacetone. However, in terms of PMN chemotaxis and phagocytosis, tropolone is significantly less toxic than either of te other ligands. 8-Hydroxyquinoline was found to reduce PMN chemotaxis and phagocytosis to approximately 70% of the control values at a concentration of 20 micro M. Tropolone may prove a superior labelling reagent.

Myocardial imaging with dipyridamole: comparison of the sensitivity and specificity of 201Tl versus MUGA

Myocardial imaging was performed at rest and after dipyridamole infusion using 201Tl and 99Tcm - gated blood pool studies (MUGA). Of 38 patients studied, 21 had coronary artery disease (CAD) and 17 were normal. With 201Tl imaging, 19 of 21 patients with CAD (sensitivity 88%) showed perfusion defects during dipyridamole. Of 17 normals 6 (specificity 65%) showed clear perfusion defects during dipyridamole. With MUGA, 2 of 15 patients with CAD (sensitivity 13%) developed abnormal wall motion during dipyridamole; both patients developed ST depression greater than 1 mm. Of 10 normals none developed abnormal wall motion. Twenty six of 38 patients developed angina during dipyridamole, which was reversed by aminophylline in 24 of 26. We suggest that dipyridamole infusion is effective for 201Tl-perfusion imaging, and easily performed, but is not suitable for MUGA studies where ischaemia is the required endpoint.

Whole-body and exchangeable potassium measurements in normal elderly subjects

A comparison of total body potassium status of eighteen healthy subjects with normal renal function in the age group 65-85 years, measured by whole body counting and by total exchangeable potassium on plasma and urine samples taken at 24h, shows that there is no delay in exchange in radioactive potassium in the elderly, and that the exchangeable method gives a reliable value of total body potassium. The results suggest that the normal range for potassium per kilogramme body weight is lower for old persons than for younger age groups.

Displacement of the spleen in infected pancreatic pseudocyst: case report

In two patients with infected pancreatic pseudocyst 99mTc-sulfur colloid scans showed similar medial and inferior displacement of the spleen.

Radioisotope measurements of regional lung function in bronchogenic carcinoma

Five out of 300 patients with bronchogenic carcinoma referred for pre-operative radioisotope imaging showed perfusion losses markedly in excess of regional ventilation impairment, a finding previously reported as being typical for pulmonary thrombeembolism.