Abstract
High-activity radioactive iodine (RAI) therapy for metastatic thyroid cancer (TC) requires isolation to minimize radiation exposure to third parties, thus posing challenges for patients needing hands-on care. There are limited data on the approach to high-activity RAI treatment in paraplegic patients. We report a state-of-the-art multidisciplinary approach to the management of bedbound patients, covering necessary radiation safety measures that lead to radiation exposure levels as low as reasonably achievable. Given the limited literature resources on standardized approaches, we provide a practical example of the safe and successful treatment of a woman with BRAFV600E-mutant tall-cell–variant papillary TC and pulmonary metastases, who underwent dabrafenib redifferentiation before RAI therapy. The patient was 69 y old and had become paraplegic because of a motor-vehicle accident. Since caring for a paraplegic patient with neurogenic bowel and bladder dysfunction poses radiation safety challenges, a multidisciplinary team comprising endocrinologists, nuclear medicine physicians, radiation safety specialists, and the nursing department developed a radiation mitigation strategy to ensure patient and staff safety during RAI therapy. The proposed standardized approach includes thorough monitoring of radiation levels in the workplace, providing additional protective equipment for workers who handle radioactive materials or are in direct patient contact, and implementing strict guidelines for safely disposing of radioactive waste such as urine collected in lead-lined containers. This approach requires enhanced training, role preparation, and practice; use of physical therapy equipment to increase the exposure distance; and estimation of the safe exposure time for caregivers based on dosimetry. The effective and safe treatment of metastatic TC in paraplegic patients can be successfully implemented with a comprehensive radiation mitigation strategy and thorough surveying of personnel for contamination.
According to the American Thyroid Association guidelines, therapy with radioactive iodine (RAI) is strongly recommended for high-risk patients with differentiated thyroid cancer (TC) as it decreases the recurrence rate and improves overall survival (1–3).
However, RAI therapy is associated with some risk that third parties will be exposed to radiation. Therefore, health care professionals must meticulously monitor and minimize radiation exposure to patients and the public during and after RAI therapy (4). According to American Thyroid Association guidelines, radiation exposure levels should be as low as reasonably achievable. That is accomplished through a mandatory 24- to 48-h radiation isolation period for patients and appropriate home, sleep, and work accommodations (3–6). Health care professionals working with radioactive materials must consider the cumulative effects of radiation exposure over time and have a whole-body dose limit of less than 50 mSv (5,000 mrem) per year (6,7). Carefully considering and implementing these recommendations can help minimize radiation exposure and ensure safety during RAI therapy.
Nevertheless, radiation safety becomes more challenging if the patient requires hands-on care during the radiation isolation period. Although there is published practical guidance on the management of patients who are minors, are undergoing hemodialysis, or have gastrointestinal disorders rendering application of RAI therapy challenging (Table 1), to our knowledge there are no data on a comprehensive management strategy in paraplegic bedbound patients. Therefore, using current radiation safety guidelines (3–6), we propose a multidisciplinary approach to paraplegic patients based on the clinical scenario observed in our institution. We believe that our state-of-the-art approach can guide other challenging cases of RAI therapy in paraplegic patients with neurogenic bowel and bladder dysfunction.
Individualized RAI Therapy Safety Strategy in Unique Differentiated TC Patients
CLINICAL SCENARIO
A 69-y-old woman with pT4aN1bM1 BRAFV600E-mutant papillary TC, paraplegic because of a motor-vehicle accident in 1993, initially underwent total thyroidectomy with bilateral central and right lateral neck dissection in 2017. Six months later, she received 5,550 MBq (150 mCi) of RAI, with posttreatment scans revealing several foci of uptake within the thyroid bed and bilaterally in the breasts but no visible lung metastases, despite chest CT depicting several subcentimeter pulmonary nodules associated with a thyroglobulin level elevated to 81.1 ng/mL, suggesting non–RAI-avid pulmonary metastases. In 2021, progressive lung disease was noted. Right-sided video-assisted thoracic surgery with wedge resection was performed to characterize the tumor molecularly, and the BRAFV600E pathogenic variant was identified in the metastatic lesions.
Given the disease progression and its non–RAI-avid nature, redifferentiation therapy with dabrafenib, 150 mg orally twice daily, was initiated. Three months later, diagnostic dosimetry with 74 MBq (2 mCi) of 131I under levothyroxine withdrawal revealed redifferentiation with profoundly RAI-avid pulmonary metastases, and RAI therapy was deemed suitable (Fig. 1A). On the basis of dosimetry estimates, the maximum safe activity that would not exceed 2,000 mSv (200 rads) to the bone marrow was determined to be 14,800 MBq (400 mCi), but the maximum safe activity that would not exceed 2,960 MBq (80 mCi) retention in the lungs at 48 h was determined to be 8,251 MBq (223 mCi). Hence, therapy with 7,400 MBq (200 mCi) of RAI was pursued.
NOTEWORTHY
Caring for a patient with paraplegia during radiation isolation poses uncommon challenges to hospital staff but can be resolved with individualized care.
Radiation mitigation can be achieved through enhanced training, physical therapy equipment to increase the physical distance from the patient during direct care, careful monitoring of exposure time, contamination surveys, and strict guidelines for safely disposing of radioactive waste.
Dosimetry-based therapy with RAI facilitates individualized care and allows accurate prediction of the radiation exposure to dose-limiting organs such as bone marrow and the lungs.
Ultimately, the therapy was safely and successfully conducted without any immediate complications. Five days later, posttreatment whole-body scanning revealed extensive lung uptake, lower neck uptake, and upper mediastinal lymph node uptake. The thyroglobulin level decreased from 4,111 ng/mL at the time of therapy with RAI to 48.4 and 24.2 ng/mL at 6 and 12 mo, respectively (Fig. 1B), and the pulmonary lesions substantially decreased in size and number (Fig. 1C). Pulmonary function testing after therapy revealed a moderately restrictive pattern comparable to that on the baseline evaluation and no change in diffusion capacity per alveolar volume, which remained within the reference range at baseline (76%) and after therapy (81%).
(A) Diagnostic 131I scan under levothyroxine withdrawal performed at baseline (no RAI uptake, left panel), after 3 mo of redifferentiation therapy with dabrafenib (induced RAI uptake, middle panel), and after therapy (right panel) documenting reinduction of RAI uptake. (B) Thyroglobulin trends during follow-up period indicating significant decrease in tumor marker levels at 6 and 12 mo after RAI therapy. (C) CT scans documenting resolution of nodules (arrows) present at baseline and absent 12 mo after RAI therapy. Tg = thyroglobulin; TSH = thyroid-stimulating hormone; WB = whole-body.
RADIATION MITIGATION STRATEGY FOR PARAPLEGIC PATIENT
Our institution supports the administration of radiopharmaceuticals in compliance with the U.S. Nuclear Regulatory Commission requirements for radiation safety. Hence, patients are placed in isolation when they receive a therapeutic activity of 131I exceeding 1,221 MBq (33 mCi) and are released when the exposure rate 1 m away from the patient falls below 70 μSv (7 mrem)/h (Nuclear Regulatory Commission, 2016) (6,7).
For radiation exposure and contamination control, patients are isolated in an uncarpeted private room with dedicated sanitary facilities constructed with 6.35-mm (¼-in) lead shielding in the door and walls. Surfaces likely to be contaminated are covered with plastic-backed absorbent paper or wrapped in plastic. A series of maximum suggested stay times is provided for different interactions with the patient, as necessary. Since patient–staff interactions on a regular basis are limited to medical emergencies while a patient is in isolation, and this patient required ongoing direct care due to paraplegia, the standard practice was modified. The modifications included emptying the patient’s bowels before dosing with RAI; inserting a Foley catheter to avoid leakage; housing the urine bag in a lead-lined container; using adult diapers, and changing them as necessary to ensure dryness; using a specialized Dolphin bed (Joerns Healthcare) to reduce the risk of pressure ulcers; and using hospital bed trapezes and a turning-and-repositioning system to allow patients to collaborate with the repositioning that was necessary every 2–4 h. A workflow was designed, and dry runs were practiced to familiarize staff with their individual roles and to identify vulnerabilities in the contamination control plan. Stay times were estimated for individuals on the basis of historical effective dose equivalent values following the care of typical patients receiving a similar prescribed activity (Fig. 2).
Comparison of caregiver radiation exposure means within dosimeter-wearing periods. Target period is outlined in group 6, revealing mean staff exposure of <0.01 mSv (<1 mrem). The 2 outliers in group 6 are health physics employees and are below dosimeter-wearing period trigger limit of 0.5 mSv (50 mrem).
Significant contamination control measures were adopted. The patient room and staging area were connected by a 2-lane path, and all surfaces were covered with disposable materials. For each entry, posted safety sheets were updated with current 30-cm and 1-m isodose lines and on-contact exposure rates. In the staging area, 2 members of the nursing staff and 1 member of the radiation safety staff donned full personal protective equipment, including a full-body Tyvek suit (DuPont), double gloves, booties, and a face covering. These staff entered the patient room via lane 1 and exited via lane 2. Although the nurses provided immediate care needs, the radiation safety staff member emptied the shielded Foley catheter, organized clutter, and packaged radioactive waste containers. After completing their duties and exiting the patient room, the staff removed personal protective equipment and performed a full personnel contamination survey in the staging area (Fig. 3).
Patient room precautions during RAI therapy, featuring 2-lane path and disposable materials. PPE = personal protective equipment.
The average whole-body radiation dose to staff was 0.12 mSv (12 mrem) per dosimeter-wearing period, with a maximum of 0.37 mSv (37 mrem) (target period) and a minimum of 0.01 mSv (1 mrem), which are within recommended safety limits (Fig. 2). The total recorded dose to staff per wearing period was influenced by the type and number of treatments with which each staff member was involved; staff support for multiple RAI-treated and 177Lu-DOTATATE–treated patients was included. The generalized estimated effect size was used to measure the variability in the total recorded whole-body dose in terms of the number of RAI treatments per wearing period. The analysis showed that 27% of the change in the total recorded measurements per wearing period could be attributed to the number of RAI treatments (Fig. 2). We identified 2 whole-body-dose outliers in the target period in group 6 (Fig. 2). These outliers were health physics staff who both handled and administered the 131I capsules and regularly changed the Foley bag. The health physics staff commonly handled larger amounts of radioactivity during this 2-mo dosimeter-wearing period because they supported different treatments at our center within this time frame. Their recorded dose during this period was less than the dosimeter-wearing period trigger limit of 0.5 mSv (50 mrem) set by the Division of Radiation Safety at our institution.
DISCUSSION
Patients with progressive RAI-refractory TC have poor outcomes, with a 10-y survival rate of 10% (8). Given our patient’s progressive metastatic disease, the severity of her prognosis made it imperative to resensitize non–RAI-avid tumors to enable RAI therapy (9,10). Although paraplegia in our patient was not TC-related, there are TC patients with spinal metastases causing paraplegia (11–13). Treatment directed toward the metastatic locus with either neurosurgery or local targeted radiation is preferable in such patients (11), but there are also cases of spinal metastases treated with RAI therapy (14,15). Unfortunately, to our knowledge there are no data on radiation safety measures implemented in these clinical scenarios.
Our patient posed a radiation safety challenge for caregivers, as she required continuous medical support while in the radiation isolation room. Our analysis demonstrates that the adaptations made in this case were effective in maintaining an individual occupational dose as low as reasonably achievable. Although the overall staff burden was over 3 times the average per period, there was no detectable increase in individual whole-body exposure doses beyond the safety limits. Several key changes to the standard procedures can be attributed to this success. First, limiting exposure time by dividing caregiver shifts significantly reduced all individual exposure periods. The effective use of accurate and up-to-date isodose maps allowed the staff to better understand and manage their individual distance from the source within the work environment. Shielding staff from unnecessary exposure and maintaining an orderly environment reduced the risk of radiation contamination. The adaptations also included significant changes in the use of personal protective equipment and required elevated contamination control measures. These changes demanded extensive staff training tailored toward this patient’s needs, which likely significantly contributed to the success in managing this challenging patient (16).
CONCLUSION
The effective and safe treatment of metastatic TC in paraplegic patients can be successfully implemented with a comprehensive radiation mitigation strategy and thorough personnel contamination surveys.
DISCLOSURE
This work was supported in part by the Intramural Research Program of the U.S. National Institute of Diabetes and Digestive and Kidney Diseases. No other potential conflict of interest relevant to this article was reported.
Footnotes
Published online Jul. 11, 2024.
- © 2024 by the Society of Nuclear Medicine and Molecular Imaging.
REFERENCES
- Received for publication February 8, 2024.
- Accepted for publication May 22, 2024.
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