Technetium-99m-tetrofosmin: retention of nitrogen atmosphere in kit vial as a cause of poor quality material.

Technetium-99m (99Tc(m))-tetrofosmin was prepared using four different reconstitution methods. The radiochemical purity (RCP) of these products was assessed 8 h later using thin layer chromatography (TLC). Material produced using the original method supplied by the manufacturer and using an newer method, which involves the use of a vent needle and the addition of air, had acceptable RCP (mean +/- SD 94.2 +/- 1.1% and 94.7 +/- 1.7%, respectively) and similar chromatograms. In addition, both products showed good clinical efficacy and exhibited normal biodistribution behaviour. Preparing 99Tc(m)-tetrofosmin using the two other methods, one using a high radioactive concentration and the other maintaining the nitrogen content of the kit vial, gave rise to chromatograms with reduced RCP (63.5 +/- 10.9% and 61.9 +/- 7.6%, respectively) and greater levels of impurities. Although neither of these last two preparations was used clinically, we suggest that reports of poor quality images may be the result of administration of materials similar to these. Results for the high radioactive concentration method were as expected and are consistent with the restrictions imposed by the manufacturer. However, results using the last method are surprising and would suggest that the production of good quality 99Tc(m)-tetrofosmin is dependent on the quantity of nitrogen in the kit vial. We believe that the amount of nitrogen removed from the kit vial during the process of reconstitution is critical. If too much nitrogen is present this will result in poor quality material. In practice it is conceivable that there could be occasions when insufficient nitrogen is removed when following the manufacturer's original guidance, thereby leading to low RCP material. To ensure adequate nitrogen is removed during reconstitution, adoption of the manufacturer's revised method, involving the deliberate introduction of air, is therefore appropriate.

A study of doses to the hands during dispensing of radiopharmaceuticals.

Radiation doses to both the fingertip and finger base of staff preparing radiopharmaceuticals in a radionuclide dispensary have been monitored for more than 5 years. The records show a fall in dose thought to be due, largely, to the introduction of all-glass (lead) syringe shields. In 1998, the annual radiation dose (mean +/- standard deviation) to the fingertip had fallen to 83+/-11 mSv, which corresponded to 0.18 mSv per 10 GBq 99Tc(m) handled. There was less reduction in dose to the finger base, which, in 1998, was 70% of that to the fingertip. To study the effect of a syringe shield on the distribution of dose across the hands, model hands were constructed and a gamma extremity monitoring system (GEMS) was used to measure dose. When a radiopharmaceutical is dispensed, contributions to the dose from activity in the vial and syringe change during the procedure. As a result, relative doses to different fingers and the ratios of doses to the tip and base of each finger will fluctuate throughout dispensing. In the absence of a syringe shield, the front tip of the index finger received the greatest radiation dose. When a syringe shield was used, doses were lower and the dose distribution was completely different. These findings have important implications in terms of compliance with the new UK Ionizing Radiations Regulations, where the dose limit is applied to 'the dose averaged over any area of 1 cm2 regardless of the area exposed'.

No-carrier-added 123I-MIBG: an initial clinical study in patients with phaeochromocytoma.

Radioiodinated meta-iodobenzylguanidine (MIBG) is used routinely for imaging and targeted radiotherapy of tumours derived from the neural crest. Since active uptake of MIBG by the noradrenaline transporter (NAT) makes a greater contribution to total drug accumulation than passive uptake when MIBG is present at low concentrations, tumour-specific uptake should be enhanced by the administration of lower molar amounts of MIBG. This could be achieved through the use of MIBG with a high specific activity. Commercially available preparations of 123I-MIBG have specific activities of approximately 200 MBq.mg-1. We have synthesized and used no-carrier-added (n.c.a.) 123I-MIBG produced by an iododesilylation reaction (specific activity 0.7 TBq.mg-1). We report here the first clinical studies comparing the commercially available and n.c.a. MIBG diagnostic preparations. Five patients with known phaeochromocytoma were studied. Unlike studies in animal models, no consistent improvement in tumour uptake was observed with the n.c.a. material. A larger patient group is required to determine whether there are significant differences between the two preparations, before proceeding to studies at therapeutic activity levels of n.c.a. 131I-MIBG. Even with no improvement in tumour uptake, n.c.a. MIBG may be the favoured formulation for therapeutic applications to reduce the molar amount of drug injected.

99Tcm-MAG3: problems with radiochemical purity testing.

The radiochemical purity (RCP) of 99Tcm-MAG3 was determined using solid-phase extraction (SPE), high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC). The difference between the HPLC and SPE methods was highly significant (P < 0.001), yielding values for RCP of 94.4 +/- 1.4% and 86.0 +/- 5.1% [corrected] respectively (mean +/- s). Further qualitative analysis of the SPE fractions obtained, was carried out using HPLC and TLC. The unexpected presence of 99Tcm-MAG3 in one of the fractions was observed together with the appearance of hydrophilic impurities in the hydrophobic extract. This lack of specificity may be the reason for the discrepancy between the SPE and HPLC methods. Use of the SPE method leads to an underestimation of the RCP of 99Tcm-MAG3 and, indeed, had we been relied solely on this method of analysis, we would have had to reject most kits we prepared. In a separate study, we compared a TLC method with HPLC. Differences were found to be highly significant (P < 0.001), yielding values of 98.3 +/- 0.6% and 95.8 +/- 0.9% respectively. Comparison of the data points showed that TLC gave consistently higher RCP yield than HPLC. This elevated value was found to be due to the inability of the TLC method to separate 99Tcm-lipophilic impurity, seen on HPLC, from the 99Tcm-MAG3. Therefore, use of this TLC method leads to an overestimation of the RCP of 99Tcm-MAG3.

Reductions in finger doses for radiopharmaceutical dispensing afforded by a syringe shield and an automatic dose dispenser.

A gamma extremity monitoring system (GEMS) has been used to measure finger doses during radio-nuclide dispensing procedures. GEMS uses a small semi-conductor probe that can be attached to a finger from which a continuous read-out can be obtained that is related to dose rate. The pattern of dose accumulation can be analysed to allow doses received from individual operations within a procedure to be evaluated. GEMS has been used to compare the radiation dose reduction afforded by a syringe shield and an automatic dose dispenser. Dispensing procedures were simulated using 10% of the activity normally administered in order to avoid problems with detector saturation. Results show that the syringe shield and the automatic dose dispenser reduced finger doses by more than a factor of 10 for the procedures tested. The disadvantages of the automatic dispenser tested were a failure to transfer activity in 10% of cases and a longer time taken for the dispensing process. GEMS has the potential to facilitate greater optimization of finger doses through analysis of finger dose patterns.

Phase I clinical and pharmacokinetic study of PK1 [N-(2-hydroxypropyl)methacrylamide copolymer doxorubicin]: first member of a new class of chemotherapeutic agents-drug-polymer conjugates. Cancer Research Campaign Phase I/II Committee.

PK1 comprises doxorubicin covalently bound to N-(2-hydroxypropyl)methacrylamide copolymer by a peptidyl linker. Following cellular uptake via pinocytosis, the linker is cleaved by lysosomal enzymes, allowing intratumoral drug release. Radically altered plasma and tumor pharmacokinetics, compared to free doxorubicin, and significant activity in animal tumors have been demonstrated preclinically. We aimed to determine the maximum tolerated dose, toxicity profile, and pharmacokinetics of PK1 as an i.v. infusion every 3 weeks to patients with refractory or resistant cancers. Altogether, 100 cycles were administered (range, 20-320 mg/m2 doxorubicin-equivalent) to 36 patients (20 males and 16 females) with a mean age of 58.3 years (age range, 34-72 years). The maximum tolerated dose was 320 mg/m2, and the dose-limiting toxicities were febrile neutropenia and mucositis. No congestive cardiac failure was seen despite individual cumulative doses up to 1680 mg/m2. Other anthracycline-like toxicities were attenuated. Pharmacokinetically, PK1 has a distribution t(1/2) of 1.8 h and an elimination t(1/2) averaging 93 h. 131I-labeled PK1 imaging suggests PK1 is taken up by some tumors. Responses (two partial and two minor responses) were seen in four patients with NSCLC, colorectal cancer, and anthracycline-resistant breast cancer. PK1 demonstrated antitumor activity in refractory cancers, no polymer-related toxicity, and proof of principle that polymer-drug conjugation decreases doxorubicin dose-limiting toxicities. The recommended Phase II dose is 280 mg/m2 every 3 weeks. Studies are planned in colorectal, NSCLC, and breast cancer patients.

Current or recent proton pump inhibitor therapy markedly impairs the accuracy of the [14C]urea breath test.

BACKGROUND: There are increasing indications for assessing Helicobacter pylori status by non-invasive means in dyspeptic patients. There is also increasing use of proton pump inhibitor therapy for dyspeptic disease. AIMS: To determine the effect of proton pump inhibitor therapy on the accuracy of the [14C]urea breath test. PATIENTS: [14C]Urea breath tests were performed in 20 H. pylori-positive and 13 H. pylori-negative dyspeptic patients before commencing omeprazole and after 4 weeks of treatment with 40 mg/day and then 6 months of treatment with 20 mg/day. Further studies were done in H. pylori-positive patients to examine the time course of the onset and resolution of the effect observed. RESULTS: False negative results occurred in 45% of the H. pylori-positive subjects after 4 weeks of omeprazole 40 mg/day and in 28% after 6 months of 20 mg/day. False positive results occurred in 15% of the H. pylori-negative subjects after 4 weeks of omeprazole 40 mg/day. In the H. pylori-positive subjects time course studies showed increasing suppression of the breath test result over the first 2-4 weeks of treatment. It took a similar time for the breath test result to recover after stopping treatment. There was no significant change in H. pylori IgG serology in the H. pylori-positive patients after 7 months of omeprazole treatment. CONCLUSIONS: Proton pump inhibitor therapy markedly impairs the accuracy of the [14C]urea breath test and, in particular, produces a high proportion of false negative results. The effect is dose related and may persist for 2-4 weeks after stopping therapy. Patients should be carefully questioned about recent proton pump inhibitor therapy before accepting a negative breath test result as reliable.

Assessment of symptomatic response as predictor of Helicobacter pylori status following eradication therapy in patients with ulcer.

BACKGROUND: Helicobacter pylori eradication therapy is routinely used for treating patients with peptic ulcer disease. AIMS: To assess the value of symptomatic response to H pylori eradication therapy as a marker of post-treatment H pylori status. PATIENTS AND METHODS: One hundred and nine dyspeptic patients with active duodenal or gastric ulceration association with H pylori infection had their symptoms measured by a validated questionnaire before and three months following H pylori eradication therapy. The symptomatic response was compared with post-treatment H pylori status as determined by the 14C urea breath test. RESULTS: An eradication rate of 84% was achieved. Of the 92 patients eradicated of H pylori, 47% experienced complete or near complete resolution of dyspepsia. Of the 17 patients in whom the infection was not eradicated, only one (6%) experienced resolution of dyspepsia. Resolution of dyspepsia was therefore a powerful predictor of eradication of H pylori with a predictive value of 98%. In contrast, persistence of dyspepsia was a weak predictor of persisting infection with a predictive value of only 25%. Excluding patients with endoscopic evidence of coexisting oesophagitis and/or retrosternal discomfort or reflux at initial presentation did not increase the predictive value of persisting dyspepsia for persisting infection. CONCLUSIONS: Complete resolution of dyspeptic symptoms is a powerful predictor of eradication of H pylori infection in ulcer patients. Persistence of symptoms is a weak predictor of persisting infection and patients with persisting dyspepsia must have their H pylori status rechecked to guide future management.

Dietary sodium restriction impairs insulin sensitivity in noninsulin-dependent diabetes mellitus.

Dietary sodium restriction has a variety of effects on metabolism, including activation of the renin-angiotensin system. Angiotensin II has complex metabolic and cardiovascular effects, and these may be relevant to the effects of both nonpharmacological and pharmacological interventions in noninsulin-dependent diabetes mellitus (NIDDM). We have assessed the effect of dietary sodium restriction on insulin sensitivity and endogenous glucose production in eight normotensive patients with diet-controlled NIDDM who underwent hyperinsulinemic clamp studies in a randomized, double-blind, placebo-controlled cross-over protocol after two 4-day periods on sodium replete (160 mmol/day) and sodium deplete (40 mmol/day) diets. Mean +/- SD 24-h urinary sodium was 197 +/- 76.0 mmol (replete) and 67 +/- 19.5 mmol (deplete), P = 0.03. Insulin sensitivity was 42.0 +/- 11.3 mumol/kg.min (replete) and 37.0 +/- 11.6 mumol/kg.min (deplete), P = 0.04 (a reduction of 12%). Blood pressure was 130 +/- 21/78 +/- 11 mmHg (replete) and 128 +/- 12/73 +/- 10 mmHg (deplete). Dietary sodium restriction may result in a decrease in peripheral insulin sensitivity in normotensive patients with NIDDM, possibly via an elevation in prevailing angiotensin II concentrations.

Comparison of helisal rapid blood test and 14C-urea breath test in determining Helicobacter pylori status and predicting ulcer disease in dyspeptic patients.

OBJECTIVE: Noninvasive tests for Helicobacter pylori are used increasingly. Our aim was to compare the Helisal Rapid Blood (HRB) test and 14C-urea breath test (UBT) for determining H. pylori status and predicting ulcer disease. METHODS: Three hundred fifty-one consecutive patients with dyspepsia (mean age 40 yr; range 16-77 yr) had an HRB test and UBT followed by endoscopy with biopsies of the antrum and body for histology and antral urease slide test (CLO test). Patients were excluded if they had previously confirmed ulcer disease, gastric surgery, or anti-H. pylori therapy or were taking nonsteroidal anti-inflammatory drugs. RESULTS: Sixty-three percent of the patients were "gold standard" H. pylori positive (positive CLO test, positive staining), 34% were gold standard negative (negative CLO test, negative staining), and 3% had conflicting CLO test and histology. The UBT was superior to HRB for determining H. pylori status (sensitivity 98% vs 92%, p = 0.04; specificity 100% vs 69%, p < 0.001). The specificity of the HRB decreased with increasing patient age (74% for age <46 yr; 57% for age > or =46 yr). A negative UBT was superior to a negative HRB test for predicting the absence of ulcer disease (47% vs 36 %; p < 0.01). A positive UBT was similar to a positive HRB in predicting the presence of ulcer disease (92% vs 84%; p = 0.23). CONCLUSIONS: The HRB test is inferior to the UBT for determining H. pylori status. The tests have a similar ability to predict the presence of ulcer disease when positive, but a negative UBT is a better predictor of the absence of ulcer disease.

The Helicobacter pylori breath test: a surrogate marker for peptic ulcer disease in dyspeptic patients.

BACKGROUND: There is interest in noninvasive H pylori testing as a means of predicting diagnosis and determining management in dyspeptic patients. AIMS: To assess the value of the 14C urea breath test as a predictor of peptic ulcer disease in patients presenting with dyspepsia. PATIENTS AND METHODS: 327 consecutive patients referred for investigation of dyspepsia had a 14C urea breath test performed before endoscopy. Patients were not included if they had previously confirmed ulcer disease, previous gastric surgery, or were taking non-steroidal anti-inflammatory drugs. RESULTS: Of the 182 patients with a positive 14C urea breath test, duodenal and/or gastric ulcers were present in 45% and erosive duodenitis in a further 2%. Oesophagitis was present in 12% of the breath test positive patients with two thirds of the oesophagitis patients having co-existent ulcer disease. The prevalence of ulcer disease in the H pylori positive dyspeptic patients was independently related to smoking and previous investigation status. If previously uninvestigated, the prevalence of ulcers was 67% in smokers and 46% in non-smokers. If previous upper gastrointestinal investigations were negative, the prevalence of ulcers was 53% in smokers and 28% in non-smokers. Of the 136 patients with a negative breath test, only 5% had peptic ulcers. The most frequent endoscopic finding in these H pylori negative subjects was oesophagitis, being present in 17%. CONCLUSIONS: This study demonstrates that a positive H pylori test is a powerful predictor of the presence of underlying ulcer disease in dyspeptic patients, especially if smokers, and that a negative H pylori test is a powerful predictor of the absence of ulcer disease. It also indicates that a negative upper gastrointestinal investigation does not preclude subsequent presentation with ulcer disease.

The radiation dose to the urinary bladder in radio-iodine therapy.

A new MIRD dynamic model has been used to provide estimates of the dose to the urinary bladder resulting from the administration of the therapeutic agents 131I as iodide (for thyroid carcinoma) and 131I meta-iodobenzylguanidine (MIBG) (for neuroendocrine tumours). Because the latter agent is used for therapeutic purposes in children, dose estimates were obtained for subjects aged 1 year and upwards. Those parameters likely to influence the bladder dose were also investigated, making use of the inherent flexibility of the model. For an administration of 1 GBq of either 131I as iodide or 131I MIBG to an adult subject, the radiation dose to the inner surface of the bladder was estimated to be approximately 1100 mGy, which is nearly twice the value estimated using a constant-volume bladder model. The new model produced dose estimates for children (within the range 1000-2750 mGy GBq-1 of 131I MIBG) which were approximately 50% greater than those derived using a constant-volume bladder model. The urine flow rate was found to have the greatest effect on the bladder dose, a flow of twice the normal rate resulting in a reduction in the bladder dose by a factor of two. On the other hand, a reduction in the urine flow rate to half the normal value was estimated to increase the radiation dose by a factor of two. This was true for subjects of all ages. With normal voiding, the average dose to the bladder wall from 131I beta-radiation was estimated to be 5-13% of the surface beta dose for subjects of different ages, the values being greater in children. This has to be compared with a photon contribution to the average bladder wall dose amounting to 10-20% of the combined surface dose both from beta-particles and from photons.

Dosimetric considerations in 131I-MIBG therapy for neuroblastoma in children.

Dosimetric calculations have been made for organ doses in patients receiving 131I-MIBG therapy as treatment for neuroblastoma. As well as whole body and liver dose, consideration has been given to dosimetry of organs (lung, urinary bladder) whose tolerance may become treatment limiting when 131I-MIBG is given as part of combined modality therapy. Data from both adults and children receiving radiolabelled MIBG for diagnostic or therapeutic purposes have been compared in constructing dosimetry models for children. A recently published urodynamic model has been used in the estimation of radiation dose to the bladder. The results show that liver and lung may receive doses greater than the average total body dose (0.58 mGy MBq-1 and 0.35 mGy MBq-1, respectively, as compared with 0.25 mGy MBq-1 to the whole body). The organ dose estimates do not differ greatly from previous analyses except in the case of the bladder for which the new modelling studies have resulted in lower dose estimates (0.76 mGy MBq-1 administered, for dose to bladder surface from bladder contents) than in some published series. This may result from differing assumptions regarding parameters such as bladder content and urine flow rate, an enhanced fluid intake being assumed in the present bladder dose estimates. Average doses to the bladder wall from the contents were estimated to be 7.4-11.3% of the surface doses. The urodynamic modelling analysis shows that the bladder could receive a much greater dose (by an order of magnitude) in patients who were inadequately hydrated or had impaired renal function.

Multi-modality megatherapy with [131I]meta-iodobenzylguanidine, high dose melphalan and total body irradiation with bone marrow rescue: feasibility study of a new strategy for advanced neuroblastoma.

New therapeutic approaches are needed for advanced neuroblastoma as few patients are currently curable. We describe an innovative strategy combining [131I]meta-iodobenzylguanidine ([131I]mIBG) therapy with high dose chemotherapy and total body irradiation. The aim of combining these treatments is to overcome the specific limitations of each when used alone to maximise killing of neuroblastoma cells. Five children received combined therapy with [131I]mIBG followed by high dose melphalan and fractionated total body irradiation. Autologous bone marrow transplantation was undertaken in 3 patients and allogeneic in 2 patients. One patient received additional localised radiotherapy to residual bulk disease. One patient is alive without relapse 32 months after treatment. 4 patients relapsed after remissions of 9, 10, 14 and 21 months. These results indicate that this combined modality approach is feasible and safe, but further evaluation is necessary to establish whether it has advantages over conventional megatherapy using melphalan alone.