A study of 50 pediatric treatments with 131I-mIBG, 177Lu-DOTATATE, and 131I-NaI found that among 100 caretakers, only 1 was exposed to radiation that exceeded nationally recommended levels.9 Another study evaluated 12 pediatric patients undergoing 131I-mIBG for neuroblastoma and found that the mean external radiation dose in caregivers was 5.8 plus or minus 7.2 mSv (range, 0.8-19.9 mSv), and caregivers of children younger than 4 years were exposed to substantially more radiation compared with caregivers of older children (exposure to 16.4 mSv vs 1.9 mSv, respectively; P = .012).10 Another study found that caregivers of pediatric patients receiving I-mIBG for neuroblastoma experienced mean radiation doses of 1.88 mSv, with the maximum potential at 1 month for 11.9 mSv.11 In this study, 97% of the familial radiation exposure occurred during the first 120 hours after I-mIBG administration.

Strategies to Reduce Incidental Exposure

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For patients with implanted or systemic radiation therapy, exposure to family members is dependent on the dose of radiation and the physical distance from the person and/or the implants. Because of the NRC guideline, patients will not be released until the medical staff feels that exposure levels to other individuals can be appropriately mitigated.

An algorithm has been developed — based on individual patient exposure situations — that can better estimate the precaution times that would be required for caregivers of patients who have been treated with Pd-103 and I-125 to remain safe.4 This allows clinicians to make more specific precaution recommendations that, in many cases, are less restrictive than arbitrary recommendations.

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For patients receiving radioactive iodine therapy, the American Thyroid Association recommends that patients maintain distance from other individuals to avoid contamination from inadvertent exposure to the patient’s bodily fluids.12 For example, patients should sleep alone in a separate bed for up to 11 days and stay home from work for up to 5 days following treatment with radioactive iodine. Other precautions, which typically last for up to 3 days, include avoiding travel by public transportation for and prolonged car rides; do not prepare food for others or share utensils; sit to urinate and flush the toilet 2 to 3 times, maintain a distance of about 6 feet from others. Patients should maintain a distance of at least 6 feet from pregnant women and children for up to 5 days.

For brachytherapy, the instructions will vary depending on the formulation of the radioactive seeds. Therefore, patients should educate themselves and carefully review the instructions given to them by their radiation treatment team. Seeds that are self-contained pose very little risk of radiation exposure to others by way of the seeds’ vicinity, but radiation from the seeds may still be present in body fluids.13 In this case, patients should, for example, avoid sharing utensils and towels. For most patients, however, radioactivity is not present in body fluids.


Patients receiving transient radiation therapy do not pose a risk of exposing family members to radiation. Modalities such as implants or systemic therapy can expose other individuals to radiation, depending on the dose and formulation of the radioactive material. Patients receiving radioactive iodine therapy for thyroid cancer pose the greatest risk of radiation exposure to others, but precautions can be taken to limit exposure to unsafe levels.


  1. United States Nuclear Regulatory Commission. Release of individuals containing unsealed byproduct material or implants containing byproduct material. 10 CFR 35.75. https://www.nrc.gov/reading-rm/doc-collections/cfr/part035/part035-0075.html. Updated August 29, 2017. Accessed October 25, 2018.
  2. American Society for Radiation Oncology. Radiation therapy for cancer [patient brochure]. Arlington, VA. http://www.rtanswers.org/uploadedFiles/Patient_Materials/RadiationTherapyForCancer.pdf. Accessed October 17, 2018.
  3. American Society for Radiation Oncology. Radiation therapy for prostate cancer [patient brochure]. Arlington, VA. http://www.rtanswers.org/uploadedFiles/Patient_Materials/ProstateCancer.pdf. Accessed October 17, 2018.
  4. Dauer LT, Kollmeier MA, Willamson MJ, et al. Less-restrictive patient-specific radiation-safety precautions can be safely prescribed after permanent seed implantation. Brachytherapy. 2010;9(2):101-111.
  5. Hanada T, Yorozu A, Shinya Y, et al. Prospective study of direct radiation exposure measurements for family members living with patients with prostate 125I seed implantation: evidence of radiation safety. Brachytherapy. 2016;15(4):412-419.
  6. Neustadter D, Barnea G, Stokar S, Corn B. Analysis of dose to patient, spouse/caretaker, and staff, from an implanted trackable radioactive fiducial for use in the radiation treatment of prostate cancer. Med Phys. 2010;37(3):1220-1224.
  7. Kuo S-F, Ho T-Y, Liou M-J, et al. Higher body weight and distant metastasis are associated with higher radiation exposure to the household environment from patients with thyroid cancer after radioactive iodine therapy. Medicine (Baltimore). 2017;96(35):35-42.
  8. Poon N, Chaudakshetrin P, Sritongkul N, Tuntawiroon M. Total effective dose equivalent to caregivers from hospitalized patients treated with high dose radioiodine for thyroid carcinoma. J Med Assoc Thai. 2016;99(2):225-230.
  9. Gains JE, Walker C, Sullivan TM, et al. Radiation exposure to comforters and carers during paediatric molecular radiotherapy. Pediatr Blood Cancer. 2015;62(2):235-239.
  10. Han S, Yoo SH, Koh KN, Lee JJ. Estimated internal and external radiation exposure of caregivers of patients with pediatric neuroblastoma undergoing 131I metaiodobenzylguanidine therapy: a prospective pilot study. Clin Nucl Med. 2017;42(4):271-274.
  11. Willegaignon J, Crema KP, Oliveira NC, et al. Pediatric 131I-MIBG therapy for neuroblastoma: whole-body 131I-MIBG clearance, radiation doses to patients, family caregivers, medical staff, and radiation safety measures. Clin Nucl Med. 2018;43(8):572-578.
  12. American Thyroid Association. Radioactive iodine FAQ. https://www.thyroid.org/radioactive-iodine/. Accessed October 17, 2018.
  13. Peirce A. Answers to Common Questions about Radiation Safety. Memorial Sloan Kettering Cancer Center. https://www.mskcc.org/blog/answers-common-questions-about-radiation-safety. Published April 3, 2014. Accessed October 17, 2018.