Answer to Question #11069 Submitted to "Ask the Experts"

My father is receiving treatment for advanced-stage prostate cancer with ²²³Ra. As this is a relatively new medicine, I can't find much information about caregiver safety. After treatment, he was told simply to "flush twice" and to use separate utensils. As his primary caregiver, my mother was told to wear gloves while handling his waste. I would like to know specific equivalents for caregiver exposure should anyone accidentally come in contact with any waste or bodily fluids. For example, if saliva on pillows or bedding is accidentally touched, what would that equal in terms of normal daily radiation exposure? Is washing patient utensils in the dishwasher enough to clear them of contamination, and can they be washed with family utensils? If my young children sit on the sofa with their grandfather for several hours, what is their exposure risk?

Very few precautions are necessary to protect household members from ²²³Ra and the radiation doses around individuals administered ²²³Ra are low. Here’s the scoop.

Radium-223 is eliminated by the body mainly in feces and urine. It may also be present in blood. I have found no information that it is present in saliva or sweat (including in U.S. Food and Drug Administration documents containing pharmacokinetics data). Animal studies showed the only soft tissues with raised levels of ²²³Ra after administration are the intestines, kidneys and spleen. The first two organs are due to the ²²³Ra in feces and urine, respectively. Radium-223 is also mostly an internal hazard, that is, the radiation dose from it is much higher when it is in the body than when it is outside of the body. 

Considering the above, good personal hygiene is the key precaution. “Flushing twice” is intended to reduce the amount of fecal material and urine that remains after the first flush. If you have small kids who play in the toilet water (reminiscent of an old Bill Cosby routine) or pets that use it as a water bowl (I had a dog that would lift the lid to get a drink), then cleaning the bowl after its use might be something to consider. 

The advice to use separate utensils is a standard precaution for certain other radiopharmaceutical therapies (e.g., treatment of thyroid disease with ¹³¹I) in which elimination routes include saliva and sweat. It may have been suggested for ²²³Ra because it seems like a good idea considering past precautions. (Like you said, this is a relatively new radiopharmaceutical treatment.) If there were any ²²³Ra on utensils, it would be easily removed by washing. I would have no concerns with washing utensils together with other household members in the dishwasher. Saliva on pillows or bedding is not easily transferred from fabric to hand to mouth. Again, there is no evidence that ²²³Ra is present in saliva. (None of the animal studies showed elevated levels in salivary glands.)

There is one other element regarding precautions, and that is time. Most of the ²²³Ra in feces and urine is eliminated in the first two days, and after four days there is very little ²²³Ra in feces and urine, or circulating in the blood. 

In response to questions from the U.S. Nuclear Regulatory Commission (NRC), Bayer, the producer of this pharmaceutical, estimated doses to individuals from patients to be less than 0.7 µSv from radiation emitted from the patient’s body. This dose assumes that the household member is 1 meter from the patient six hours a day from the time the treatment is given until all the ²²³Ra is gone. This is less than the average daily radiation exposure from radiation in the environment (background radiation) which is about 0.8 µSv. 

Bayer also estimated the average dose from uptakes by household members to be on the order of 6 µSv. Clearly, the actual dose is strongly influenced by the precautions taken, but this gives an idea of what might be a typical dose. (Note: Bayer used conservative assumptions, that is, assumptions that led to higher dose estimates in both this calculation and the calculation in the previous paragraph.)

In summary:

1. Be especially fastidious for the first two to four days after administration when dealing with urine and feces, using gloves when necessary and washing hands thoroughly (sing “Happy Birthday” two times while washing). Have your father sit to urinate. Maybe spend a little extra effort to keep the toilet and area around it clean. After two to four days, practicing good personal hygiene is important, but for standard and obvious reasons.
2. Do not be concerned about letting your kids spend time with their grandfather. Their total radiation dose will be about the same as one to two days of background radiation. And your kids and their grandfather will both benefit from spending time together.

Kent Lambert, CHP