Radiation precautions for inpatient and outpatient 177Lu-DOTATATE peptide receptor radionuclide therapy of neuroendocrine tumours

Background

¹⁷⁷Lu-DOTATATE peptide receptor radionuclide therapy is administered to patients on an inpatient and outpatient basis for the treatment of well-differentiated, metastatic neuroendocrine tumours. Following administration, these patients present an external radiation hazard due to the gamma emissions of lutetium-177. The purpose of this study was to determine precautions to be observed by ¹⁷⁷Lu-DOTATATE patients to restrict the dose received by patients’ family members to less than 5 mSv in 5 years and members of the public to less than 1 mSv per year in line with the current UK legislation. Retrospective data from therapeutic administrations of ¹⁷⁷Lu-DOTATATE (Mallinckrodt Pharmaceuticals) and Lutathera® (Advanced Accelerator Applications) were analysed to measure activity retention at discharge. Patient dose rate measurements were assumed to follow the same activity decay curve as that derived from a least squares fit of geometric mean counts in planar whole-body scans performed at four time points post-administration. Combining this with social contact times, the cumulative dose received through contact with the patient was estimated and an iterative process used to determine the length of contact restrictions to ensure the relevant dose constraints are not exceeded.

Results

On average, 36% of the administered activity was retained at the time of discharge for inpatients receiving ¹⁷⁷Lu-DOTATATE (Mallinckrodt). Retentions of 24% and 38% were measured for Lutathera® inpatients and outpatients respectively. Inpatients should restrict day contact and sleep separately from their partner for 15 days and remain off work for 5 days post-therapy. Contact with children for whom the patient is the main carer should be restricted for 16, 13 and 9 days for children below 2, 2–5 and 5–11 years respectively. One additional day is added to outpatient restriction periods, except for children aged 2–5 years which remains 13 days. No private transport restrictions are required. Patients should limit travel by public transport to 1 h on the day of discharge.

Conclusion

Restrictions are necessary to limit radiation dose to members of patients’ household and the public. Proposed precautions for inpatient and outpatient ¹⁷⁷Lu-DOTATATE therapy protocols restrict the dose received to less than the limit imposed by the UK legislation.

Electrical-thermal-structural finite element simulation and experimental study of a plasma ion source for the production of radioactive ion beams

The production target and the ion source constitute the core of the selective production of exotic species (SPES) facility. In this complex experimental apparatus for the production of radioactive ion beams, a 40 MeV, 200 μA proton beam directly impinges a uranium carbide target, generating approximately 10(13) fissions per second. The transfer line enables the unstable isotopes generated by the (238)U fissions in the target to reach the ion source, where they can be ionized and finally accelerated to the subsequent areas of the facility. In this work, the plasma ion source currently adopted for the SPES facility is analyzed in detail by means of electrical, thermal, and structural numerical models. Next, theoretical results are compared with the electric potential difference, temperature, and displacement measurements. Experimental tests with stable ion beams are also presented and discussed.

Thermal-electric coupled-field finite element modeling and experimental testing of high-temperature ion sources for the production of radioactive ion beams

In isotope separation on line facilities the target system and the related ion source are two of the most critical components. In the context of the selective production of exotic species (SPES) project, a 40 MeV 200 μA proton beam directly impinges a uranium carbide target, generating approximately 10(13) fissions per second. The radioactive isotopes produced in this way are then directed to the ion source, where they can be ionized and finally accelerated to the subsequent areas of the facility. In this work both the surface ion source and the plasma ion source adopted for the SPES facility are presented and studied by means of numerical thermal-electric models. Then, numerical results are compared with temperature and electric potential difference measurements, and finally the main advantages of the proposed simulation approach are discussed.

Age and dose-limited PET-CT scan regime in lymphoma: between the devil and the deep blue sea?

In this study the authors speculate about hypothetical effective-dose (E) reduction through limiting post-chemotherapy PET-CT scanning to lymphoma sites previously identified on pre-treatment CT. E reductions/scan time savings are compared between post-treatment standard and theoretically limited PET-CT scans. The influence of patient age with E savings and associated clinical implication for 100 subjects are discussed. The greatest E theoretical savings of 52 and 32% for the CT contribution and combined PET-CT, respectively, were seen in patients <18 y old using limited scans in this study, with a potential mean time saving of 16 min per patient across the entire cohort. However, the limited PET-CT regime here missed a 1% rate of unexpected cancer that standard PET-CT recorded. The authors recommend performing larger scale multi-centre studies comparing PET-CT pre- and post-chemotherapy to establish full clinical efficacy of this method.

A phase II study using retinoids as redifferentiation agents to increase iodine uptake in metastatic thyroid cancer

AIMS

Radio-iodine is effective in treating metastatic differentiated thyroid cancers. In 20% of cases, however, these tumours fail to take up radio-iodine, and treatment options are then limited. Failure of iodine uptake might be reversible using redifferentiating agents. Retinoids redifferentiate a variety of cell types and increase iodine uptake in thyroid tumour cells in vitro. The aim of this study was to assess whether oral isotretinoin could increase radio-iodine uptake in patients with iodine-uptake-negative metastatic thyroid cancer.

METHODS

Patients who had iodine-uptake-negative metastatic papillary or follicular thyroid cancers were selected from the thyroid database at The Royal Marsden Hospital and enrolled to an open-label, non-randomised phase II trial. Sites of metastatic disease were assessed using computed tomography or magnetic resonance imaging, and absence of iodine uptake was confirmed using a diagnostic radio-iodine scan before study entry. In eligible patients, isotretinoin was prescribed at 1.5 mg/kg/day orally for 8 weeks. Response was assessed within 2 weeks of completing treatment with repeat radio-iodine scan. All patients were reviewed every 2 weeks during treatment for assessment of toxicity.

RESULTS

Sixteen patients were treated with isotretinoin between January 2001 and July 2002: nine with metastatic papillary thyroid cancer, five with metastatic follicular cancer and two with Hurthle cell carcinoma. Median age was 57 years. All patients tolerated 8 weeks of oral isotretinoin. Mucocutaneous side-effects and minor changes in biochemical or lipid profiles were documented in most patients. In one patient, radio-iodine uptake increased after retinoid administration; however, this was not large enough to permit a significant dose of iodine to be given to sites of metastatic disease. In the other 15 patients, no radio-iodine uptake was documented.

CONCLUSION

Treatment with isotretinoin does not reliably increase radio-iodine uptake in patients with metastatic thyroid cancer. This treatment alone does not enable radio-iodine to be used for further treatment.

X-ray dose training: are we exposed to enough?

AIM

To study knowledge of radiation exposure among doctors of various grades and specialties in a large district general hospital.

METHODS

A multiple-choice format questionnaire with a total of 11 questions was distributed amongst doctors at Derriford Hospital, Plymouth, UK. Doctors of various grades and specialties completed 240 questionnaires which tested knowledge of terrestrial and medical radiation exposure.

RESULTS

With a pass mark of only 45% and a generous marking scheme, only 66 (27.5%) doctors passed. Only 15.4-25.8% of doctors knew the doses relative to a chest radiograph of various more complex procedures involving ionizing radiation and only 12.5% of doctors were aware of the one in 2000 risk of induction of fatal carcinoma from CT of the abdomen. Only 56.7% of practitioners who, under Ionizing Radiation (Medical Exposures) Regulations 2000, have responsibility for justifying procedures, passed the test. The proportion of practitioners correctly identifying the relative dose of a test to a chest radiograph varied from 30 to 56.7%, depending on the exam type. Only 20% in this group were aware of the risk of inducing a fatal cancer from a CT of the abdomen.

CONCLUSION

The study demonstrated an urgent need to improve knowledge of radiation exposure amongst doctors in clinical practice.

Diagnosis and eradication of Helicobacter pylori in patients with duodenal ulceration in the community

OBJECTIVE

To determine the value of Helicobacter pylori (Hp) serology in diagnosis of active Hp infection in patients with documented duodenal ulcer (DU) and to directly compare the efficacy and side-effects profiles of metronidazole or tinidazole in a triple therapy regimen to eradicate active Hp infection.

DESIGN OF STUDY

Prospective, single-blinded, randomised trial.

METHODS

One hundred patients from General Practice with documented DU and Hp seropositivity had a C14 Urea Breath Test (UBT). Those who tested positive were randomised to receive one-week, twice daily omeprazole 20 mgs and clarithromycin 250 mgs in combination with metronidazole 400 mgs (OCM) or tinidazole 500 mgs (OCT). Eradication was confirmed by a repeat UBT.

RESULTS

Eighty five sero-positive patients had a positive pre-treatment UBT. On intention to treat basis, OCT (100%) had a significantly better eradication rate than OCM (87.8%), p = 0.023. There was no difference in side effects.

CONCLUSION

(1) Positive Hp serology in patients with DU does not always mean active infection and (2) for patients in the community with active Hp and DU disease OCT is significantly better than OCM for eradicating Hp.

Manuka honey against Helicobacter pylori

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Physiological variations of normal transit time in children

Quantitation of the 99mTc-diethylenetriaminepentaacetic Acid (DTPA) scan yields by uptake analysis an estimate of individual kidney glomerular filtration rate (IKGFR) and by deconvolutional analysis an estimate of the mean transit time (MTT) of the non-reabsorbable tracer through the kidney. The whole kidney MTT is compounded of the renal parenchymal MTT and the rate of pelvic clearance; both functions are influenced by prevailing rates of salt and water excretion. The present study was undertaken to investigate the effect of physiological variations on the normal DTPA scan. The contralateral normal kidney in 11 children with suspected unilateral urinary tract obstruction were studied twice, first with an early morning scan (EMS) and second, 24 h later, following hypotonic volume expansion (HVE). A strong correlation was shown between urine osmolality and MTT. IKGFR was independent of the state of hydration, but in comparison to mild hydration, HVE shortened significantly (P less than 0.001) the normal whole kidney MTT, with less effect on parenchymal MTT (P less than 0.01) and therefore has its predominant effect on pelvic clearance. We advise caution in the interpretation of whole kidney transit time analysis without standardization of salt and water excretion rates. Parenchymal transit time offers a potentially useful clinical index.

The relationship between renal parenchymal mass and absolute quantitation of 99Tcm-DMSA uptake. An experimental study in the growing pig

Five Gottingen minipigs from the same litter aged 1 month entered the study and right nephrectomies were performed at staggered intervals between weeks 1 and 5. Absolute renal uptake of 99Tcm-DMSA, expressed as a percentage of the administered dose, was recorded in each animal weekly before right nephrectomy and at weekly intervals for 5 weeks post-nephrectomy. Before nephrectomy absolute renal uptake of 99Tcm-DMSA ranged between 16.8 and 21.5% (mean 18.6%) per kidney with no difference between right and left kidneys. After right nephrectomy, uptake in the left kidney approximately doubled within 1 week. No correlation was shown between renal parenchymal mass and absolute 99Tcm-DMSA uptake in paired or solitary normal kidneys undergoing growth or compensatory growth.

Immunolocalization of neuroblastoma using radiolabeled monoclonal antibody UJ13A

The monoclonal antibody UJ13A, raised after immunization of mice with human fetal brain, recognized an antigen expressed on human neuroblastoma cell lines and fresh tumors. Antibody was purified and radiolabeled with iodine isotopes using chloramine-T. In preclinical studies, 125I-labeled UJ13A was injected intravenously into nude mice bearing xenografts of human neuroblastoma. Radiolabeled UJ13A uptake by the tumors was four to 23 times greater than that by blood. In control animals, injected with a similar quantity of a monoclonal antibody known not to bind to neuroblastoma cells in vitro (FD44), there was no selective tumor uptake. Nine patients with histologically confirmed neuroblastoma each received 100 to 300 micrograms UJ13A radiolabeled with 1 to 2.8 mCi 123I or 131I. Sixteen positive sites were visible on gamma scans 1 to 7 days after injection: 15 were primary or secondary tumor sites, and one was a false positive; there were two false negatives. In two of the 15 positive sites, tumor had not been demonstrated by other imaging techniques; these were later confirmed as areas of malignant infiltration. No toxicity was encountered.

Radiolabelled leucocytes: a new diagnostic tool in occult infection/inflammation

Autologous white blood cells were labelled with Indium 111 (111In wbc) and reinjected into 18 children with suspected infection and 10 children with suspected inflammatory bowel disease aged 5 weeks to 15 years. In addition two immunosuppressed children with suspected infection received donor 111In wbc. Gamma camera images were obtained between one and four hours and 20 and 24 hours. Other appropriate investigations were also undertaken in these children. Of 18 positive 111In wbc scans 17 were true positive. There were 12 negative scans of which 9 were true negative and three were false negative. The overall results showed a sensitivity of 85%, a specificity of 90%, and an accuracy of 86%. Used appropriately this technique forms a valuable back up investigation.