Radiation Safety Observations Associated with 177Lu Dotatate Patients

Radiation exposure assessment of nuclear medicine staff administering [177Lu]Lu-DOTA-TATE with active and passive dosimetry

BACKGROUND

The use of lutetium-177 (177Lu)-based radiopharmaceuticals in peptide receptor nuclear therapy is increasing, but so is the number of nuclear medicine workers exposed to higher levels of radiation. In recent years, [177Lu]Lu-DOTA-TATE has begun to be widely used for the treatment of neuroendocrine tumours. However, there are few studies evaluating the occupational radiation exposure during its administration, and there are still some challenges that can result in higher doses to the staff, such as a lack of trained personnel or fully standardised procedures. In response, this study aims to provide a comprehensive analysis of occupational doses to the staff involved in the administration of [177Lu]Lu-DOTA-TATE.

RESULTS

A total of 32 administrations of [177Lu]Lu-DOTA-TATE (7.4 GBq/session) carried out by a physician and a nurse, were studied. In total, two physicians and four nurses were independently monitored with cumulative (passive) and/or real-time (active) dosemeters. Extremity, eye lens and whole-body doses were evaluated in terms of the dosimetric quantities Hp(0.07), Hp(3) and Hp(10), respectively. It was obtained that lead aprons reduced dose rates and whole-body doses by 71% and 69% for the physicians, respectively, and by 56% and 68% for the nurses. On average, normalised Hp(10) values of 0.65 ± 0.18 µSv/GBq were obtained with active dosimetry, which is generally consistent with passive dosemeters. For physicians, the median of the maximum normalised Hp(0.07) values was 41.5 µSv/GBq on the non-dominant hand and 45.2 µSv/GBq on the dominant hand. For nurses 15.4 µSv/GBq on the non-dominant and 13.9 µSv/GBq on the dominant hand. The ratio or correction factor between the maximum dose measured on the hand and the dose measured on the base of the middle/ring finger of the non-dominant hand resulted in a factor of 5/6 for the physicians and 3/4 for the nurses. Finally, maximum normalised Hp(3) doses resulted in 2.02 µSv/GBq for physicians and 1.76 µSv/GBq for nurses.

CONCLUSIONS

If appropriate safety measures are taken, the administration of [177Lu]Lu-DOTA-TATE is a safe procedure for workers. However, regular monitoring is recommended to ensure that the annual dose limits are not exceeded.

Individualisation of radiation protection recommendations for patients treated with [177Lu]Lu-DOTA-TATE

BACKGROUND

As for any other nuclear medicine treatment, patients treated with [177Lu]Lu-DOTA-TATE should be given some radiation protection recommendations after being discharged to limit the dose received by family members and public. The restriction periods will depend on the remaining activity at the time of discharge, the washout rate and patients' personal conditions. The activity in patients' whole-body follows a bi-exponential behaviour. At the time of discharge only the first part of the time-activity curve is known. However, the second phase of the bi-exponential curve should be known to individualize the time of restrictions. The main purpose of this prospective study was to establish a simple method for calculating the restriction periods based on measurements taken before discharge.

METHODS

The whole-body time-activity curve was calculated for 20 patients from dose-rate measurements performed during the first week post-administration. An effective decay time [Formula: see text] was calculated from a mono-exponential fit performed with the 6 h and 24 h measurements and compared with the effective decay time [Formula: see text] obtained from the mono-exponential fit performed with the 24 h, 48 h and 168 h measurements. The differences between them were calculated and the 95th percentile of these differences was used as a correction factor for [Formula: see text]. A modified effective decay [Formula: see text] was obtained by adding the correction factor to [Formula: see text] and the restriction periods for each patient was calculated. The whole body activity washout between the first and the fourth treatment cycles of 16 patients was also compared.

RESULTS

The comparison of the whole-body activity curves between the first and the fourth cycle of the treatment for 16 patients would indicate that the recommendations on radiation protection determined from the first cycle could reasonably be used for the remaining cycles in most patients. The values of [Formula: see text] and [Formula: see text] obtained for the 20 patients were significantly different. The 95th percentile of the differences between [Formula: see text] and [Formula: see text] was 46 h, which is thus the time to be added to [Formula: see text] so as to determine the restriction periods.

CONCLUSIONS

The proposed method makes it possible to calculate the restriction periods for patients treated with [177Lu]Lu-DOTA-TATE before they leave the hospital in a conservative and individualized way.

Clinical Best Practices for Radiation Safety During Lutetium-177 Therapy

IMPORTANCE

177 Lu therapy as part of theranostic treatment for cancer is expanding but it can be a challenge for sites with limited radiation protection staff to implement the radiation safety program required for therapeutic nuclear medicine.

OBJECTIVE

To increase the adoption of 177 Lu therapy, especially in smaller centers and clinics, by providing a collection of radiation safety best practices and operational experience. To provide a resource for radiation safety officers supporting the implementation of a 177 Lu therapy program.

METHODS

A panel of 11 radiation safety professionals representing sites across Canada and the United States with experience delivering 177 Lu therapy was assembled and discussed their responses to a list of questions focused on the following radiation safety topics: facility layout and design; radiation safety program; and drug management and patient care.

RESULTS

A comprehensive set of best practice guidelines for clinical radiation safety during 177 Lu therapy has been developed based on the collective operational experience of a group of radiation safety professionals. Significant findings included that 177 Lu therapy is often safely administered in unshielded rooms, that staff radiation exposure associated with 177 Lu therapy is minimal relative to other nuclear medicine programs, and that some relatively simple preparation in advance including papering of common surfaces and planning for incontinence can effectively control contamination during therapy.

CONCLUSION

The guidance contained in this paper will assist radiation safety professionals in the implementation of safe, effective 177 Lu therapy programs, even at smaller sites with limited to no experience in therapeutic nuclear medicine.

Alpha-peptide receptor radionuclide therapy using actinium-225 labeled somatostatin receptor agonists and antagonists

Peptide receptor radionuclide therapy (PRRT) has over the last two decades emerged as a very promising approach to treat neuroendocrine tumors (NETs) with rapidly expanding clinical applications. By chelating a radiometal to a somatostatin receptor (SSTR) ligand, radiation can be delivered to cancer cells with high precision. Unlike conventional external beam radiotherapy, PRRT utilizes primarily β or α radiation derived from nuclear decay, which causes damage to cancer cells in the immediate proximity by irreversible direct or indirect ionization of the cells' DNA, which induces apoptosis. In addition, to avoid damage to surrounding normal cells, PRRT privileges the use of radionuclides that have little penetrating and more energetic (and thus more ionizing) radiations. To date, the most frequently radioisotopes are β- emitters, particularly Yttrium-90 (90Y) and Lutetium-177 (177Lu), labeled SSTR agonists. Current development of SSTR-targeting is triggering the shift from using SSTR agonists to antagonists for PRRT. Furthermore, targeted α-particle therapy (TAT), has attracted special attention for the treatment of tumors and offers an improved therapeutic option for patients resistant to conventional treatments or even beta-irradiation treatment. Due to its short range and high linear energy transfer (LET), α-particles significantly damage the targeted cancer cells while causing minimal cytotoxicity toward surrounding normal tissue. Actinium-225 (225Ac) has been developed into potent targeting drug constructs including somatostatin-receptor-based radiopharmaceuticals and is in early clinical use against multiple neuroendocrine tumor types. In this article, we give a review of preclinical and clinical applications of 225Ac-PRRT in NETs, discuss the strengths and challenges of 225Ac complexes being used in PRRT; and envision the prospect of 225Ac-PRRT as a future alternative in the treatment of NETs.

Occupational radiation exposure assessment during the management of [68Ga]Ga-DOTA-TOC

Background

Since it was first approved in Europe in 2016, the gallium-68 (⁶⁸Ga) radiopharmaceutical [⁶⁸Ga]Ga-DOTA-TOC has been widely used for imaging of somatostatin receptor (SSTR) positive tumours using positron emission tomography–computed tomography (PET/CT). Significant patient benefits have been reported, so its use is rapidly increasing. However, few studies have been published regarding occupational doses to nuclear medicine personnel handling this radiopharmaceutical, despite its manual usage at low distances from the skin and the beta-emission decay scheme, which may result in an increased absorbed dose to their hands. In this context, this study aims to analyse the occupational exposure during the administration of [⁶⁸Ga]Ga-DOTA-TOC for PET/CT imaging. For this purpose, extremity, eye lens and whole-body dosimetry in terms of Hp(0.07), Hp(3) and Hp(10), respectively, was conducted on six workers with both thermoluminescent dosimeters, and personal electronic dosimeters.

Results

The non-dominant hand is more exposed to radiation than the dominant hand, with the thumb and the index fingertip being the most exposed sites on this hand. Qualitative analysis showed that when no shielding is used during injection, doses increase significantly more in the dominant than in the non-dominant hand, so the use of shielding is strongly recommended. While wrist dosimeters may significantly underestimate doses to the hands, placing a ring dosimeter at the base of the ring or middle finger of the non-dominant hand may give a valuable estimation of maximum doses to the hands if at least a correction factor of 5 is applied. Personal equivalent doses for the eyes did not result in measurable values (i.e., above the lowest detection limit) for almost all workers. The extrapolated annual dose estimations showed that there is compliance with the annual dose limits during management of [⁶⁸Ga]Ga-DOTA-TOC for diagnostics with PET in the hospital included in this study.

Conclusions

Imaging with [⁶⁸Ga]Ga-DOTA-TOC is a safe process for the workers performing the administration of the radiopharmaceutical, including intravenous injection to the patient and the pre- and post-activity control, as it is highly unlikely that annual dose limits will be exceeded if good working practices and shielding are used.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-022-00505-8.

Patient Release and Instructions for Lutetium Dotatate Radiopharmaceutical Therapy

ABSTRACT

Lutetium Dotatate radiopharmaceutical therapy (Lutathera) was approved by the United States Food and Drug Administration in 2018 and is used to treat somatostatin receptor positive neuroendocrine tumors. With all new radiopharmaceutical therapies, the radiation exposure to members of the public from the patient who received the therapy must be within regulatory limits and safe. If the patient will expose members of the public to too much radiation, the therapy must be performed on an inpatient basis. This paper shows that the administration of Lutathera can be done on an outpatient basis and provides safety and travel restrictions that should be communicated to the patient prior to leaving. The guidance presented herein serves as a basis for medical institutions looking to use Lutathera to treat patients.