Does Radiation Used During Cancer Treatment Affect Family Members?

This article covers the risk of family members being exposed to radiation during cancer treatment and strategies to limit incidental contact with potentially harmful radiotherapy byproducts.

This is one of the foremost questions for many cancer patients and their relatives: "My radiation therapy or the scans I have—will they harm the people at home, and should I avoid them?" To this question, with a few exceptions, "You can feel at ease about this" is our answer. This article specifically addresses these important questions.

Patients with cancer, regarding their family members and / or caregivers, may express concerns about their safety while the patients receive radiation therapy. The general rule is this: patients treated with radiation may leave the cancer/radiotherapy center if the total effective dose equivalent from one individual to another is not expected to exceed 5 mSv. The dose usually does not reach 5 mSv, but it may exceed 1 mSv. In this context, external, or conventional, radiotherapy in particular can be said to pose no risk to family members or caregivers, whereas high-dose systemic therapies such as radioactive iodine treatment require additional precautions.

External radiotherapy or temporary brachytherapy (internal radiotherapy)

Any radiation therapy, including external radiation treatment or brachytherapy, that is temporary poses no risk to family members. With these types of radiation therapy, patients are exposed to radiation only during active treatment, and radiation does not radiate outward from the patient's body. Family members and caregivers can be informed that they are not at risk of radiation exposure and can interact with the patient as usual.

Permanent brachytherapy and systemic radiation therapy

Permanent brachytherapy involves implanting small metal seeds that deliver radiation to the surrounding tissue. In fact, the radiation-emitting effect of this treatment is also temporary. It is most commonly used to treat prostate and cervical cancer. The implant emits radiation for a period such as several months and remains in the tissue after the radiation decreases.

Systemic treatment uses an agent that is swallowed or injected and emits radioactivity (such as radioactive iodine, RAI, for treating thyroid cancers). With both methods, the patient emits some radioactivity after leaving the treatment center, so certain precautions should be taken for some family members or other individuals.

Nevertheless, many studies have shown that family radiation exposure is very low even with these treatments. In a study of patients undergoing brachytherapy for prostate cancer, radioactive Pd-103 seeds posed very little risk of family exposure, and the researchers concluded that no additional safety precautions were needed. For I-125 seeds, no additional precautions are recommended for colleagues working with the patients or for nonpregnant or pregnant adults. Additional precautions for pregnant partners of men with prostate cancer who undergo brachytherapy with radioactive I-125 seeds are to avoid the "spooning" position when sleeping together and avoid holding children on their laps for long periods for 2 months.

Radioactive iodine was associated with similar radiation levels in a study of thyroid cancer patients receiving this treatment. In patients' own bedrooms, bathrooms and living rooms over 4 weeks after radioactive iodine treatment, total radiation was 0.45 mSv (range, 0,088-1,38 mSv), below levels considered to pose a risk to the family. Another study found that radiation levels in caregivers of thyroid cancer patients receiving high-dose radioactive iodine ranged from 0.123 mSv to 0.718 mSv, depending on the treatment dose received by the patient.

In a study of treatment with 131 I-mIBG, 177 Lu-DOTATATE and 131 I-NaI covering 50 pediatric (childhood) cancer treatments, among 100 caregivers only 1 was found to have radiation exposure exceeding recommended levels. Another study found that caregivers of pediatric patients receiving I-mIBG for neuroblastoma experienced average radiation doses of 1.88 mSv. In this study, % 97 of family radiation exposure occurred in the first 120 hours after I-mIBG administration.

Strategies to reduce incidental radiation exposure

As stated above, conventional/external radiotherapy poses no risk to people other than the patient. For patients receiving implanted (radioactive seeds placed inside the body) or systemic radiation therapy, the radiation exposure dose to family members depends on their physical distance from the person and / or implants. Patients are not discharged until exposure levels for healthcare personnel or other individuals are considered capable of being appropriately reduced.

A guideline based on individual patient exposure circumstances has been developed to better estimate the duration of precautions needed for companions of patients treated with Pd-103 and I-125 to remain safe. This allows clinicians to recommend more specific precautions, which in most cases are less restrictive than arbitrary advice.

For patients receiving radioactive iodine treatment, keeping away from other individuals is recommended to avoid contamination from accidental exposure to the patient's bodily fluids. For example, patients should sleep alone in a separate bed for up to 11 days and should not go to work but stay at home for up to 5 days after treatment with radioactive iodine. Other precautions, typically lasting up to 3 days, include avoiding public transport and long car journeys; avoiding preparing food for others or sharing objects; flushing the toilet 2 to 3 times after sitting on it; and staying approximately 6 meters away from others. Patients receiving radioactive iodine treatment should, for 5 days, remain at least 6 meters away from pregnant women and children.

For brachytherapy, protection instructions vary depending on the formulation of the radioactive seeds. Patients should therefore educate themselves and carefully review the instructions given by their radiation treatment team. For self-contained seeds, there is very little risk of exposing others to radiation through the seeds' surroundings, but radiation from the seeds may still be present in bodily fluids. In this situation, patients should, for example, avoid sharing objects and towels. However, most patients have no radioactivity in their bodily fluids.

Conclusion

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