Guidelines for outpatient I-131 radioablation therapy:

Guidelines for outpatient I-131 radioablation therapy:

From Associates in Medical Physics, LLC

On May 29, 1997, the NRC amended their regulations regarding the criteria for the release of individuals containing radioactive substances (10CFR35.75). Previously, the criteria for release was when either (1) the dose rate from the patient was <5 mrems/hr at 1 meter, or (2) the retained activity in the patient was <30 mCi. This was an activity-based release limit and it was deemed faulty because different radionuclides with the same activity will give different doses depending upon the effective half-life of the radionuclide in the body, as well as other factors that vary for different materials.

The NRC has three criteria for the release of patients from the hospital following I131 treatment [3]:

1. No individual member of the public is likely to receive more than 5 mSv (500 mrem) total effective dose equivalent from the patient in any year (1 mSv if the individual is pregnant or is 8 years old or less [1]). Verbal and written instructions describing methods to limit the dose to others must be given to the patient if an individual member of the public is likely to receive a dose exceeding 1 mSv (100 mrem) from the patient, and if the administered dose is more than 0.26 Gbq (7 mCi) [3].

2. When the survey meter reading is less than 0.07 mSv/h (7.0 mrem/h) at one meter

3. When the administered activity is 1.22 GBq (33mCi) or less

The patient should be made aware that in addition to radiation emitted directly from them, radioiodine is also excreted in body fluids such as sweat, saliva, urine, and feces [2]. After discharge patients should follow radiation safety precautions to limit radiation to other individuals these include avoiding prolonged/close contact with other people (especially infants, children, and pregnant women); mouth to mouth contact including sharing eating utensils should be avoided. The patient must sleep alone and abstain from intercourse for approximately 1 week after therapy [3]. However, other authors suggest that less stringent requirements would still result in acceptable levels of exposure to other individuals [4]. For doses between 100-200 mCi, sleeping separate for 1 day (or 3 days of sleeping apart for pregnant women and children) would still meet recommended exposure guidelines [4]. Plates and utencils used by the patient should be washed separately. Clothes may be washed separately, but this is not required [3]. The patient may use disposable dishes and utensils- however, when disposed, these may trigger sensitive waste facility alarms [3]. The patient should flush the toilet 2 times after each use and male patients should sit to urinate [3]. The physician should be reasonably certain that these instructions can and will be followed. A record documenting justification of the assigned occupancy factors and the effective half-lives used in the exposure calculations must be maintained for 3 years after the date of patient release [1].

This new regulation also discusses the dose to the breast-feeding infant or child. If that dose is likely to exceed 0.1 rem (1 mSv) - assuming no interruption of breast-feeding - instructions are required to address guidance on the interruption or discontinuation of breast-feeding and on the consequences if the patient refuses to follow the guidance. This is of particular concern with I-131 for both diagnostic and therapeutic administrations (e.g.:more than 0.4 uCi I-131). If the mother does not cease breast-feeding for this infant or child, particularly in the case of therapeutic administrations, the internal dose to the breast-feeding infant could be large enough to cause hypothyroidism or total ablation of the infant's thyroid gland. If either one of these conditions went undetected and untreated, severe mental retardation could result.

If the mother agrees to cease or interrupt breast-feeding, the new regulation indicates the time periods that breast-feeding should be interrupted for significant radionuclides (e.g.:>30 mCi Tc-99m pertechnetate - interrupt breast feeding for 6 hrs.). In the case of I-131 NaI, complete cessation for this child is recommended.

The last part of this new regulation (35.75(d) indicates that, even though instructions must be given if the dose exceeds 0.1 rem (1mSv), records of those instructions must be maintained only if the dose to the infant or child would exceed 0.5 rem (5 mSv) - (e.g.:>200 uCi Ga-67 Citrate). These records must be maintained for a period of 3 years after the release date of the patient.


[Code of Federal Regulations]
[Title 10, Volume 1, Parts 1 to 50]
[Revised as of January 1, 2000]
From the U.S. Government Printing Office via GPO Access
[CITE: 10CFR35.75]

[Page 549]

                            TITLE 10--ENERGY

                               COMMISSION

PART 35--MEDICAL USE OF BYPRODUCT MATERIAL--Table of Contents

                Subpart C--General Technical Requirements

Sec. 35.75  Release of individuals containing radiopharmaceuticals or permanent implants.

    (a) The licensee may authorize the release from its control of any
individual who has been administered radiopharmaceuticals or permanent
implants containing radioactive material if the total effective dose
equivalent to any other individual from exposure to the released
individual is not likely to exceed 5 millisieverts (0.5 rem).\1\
---------------------------------------------------------------------------

    \1\Regulatory Guide 8.39, ``Release of Patients Administered
Radioactive Materials,'' describes methods for calculating doses to
other individuals and contains tables of activities not likely to cause
doses exceeding 5 millisieverts (0.5 rem).
---------------------------------------------------------------------------

    (b) The licensee shall provide the released individual with
instructions, including written instructions, on actions recommended to
maintain doses to other individuals as low as is reasonably achievable
if the total effective dose equivalent to any other individual is likely
to exceed 1 millisievert (0.1 rem). If the dose to a breast-feeding
infant or child could exceed 1 millisievert (0.1 rem) assuming there
were no interruption of breast-feeding, the instructions shall also
include:
    (1) Guidance on the interruption or discontinuation of breast-
feeding and
    (2) Information on the consequences of failure to follow the
guidance.
    (c) The licensee shall maintain a record of the basis for
authorizing the release of an individual, for 3 years after the date of
release, if the total effective dose equivalent is calculated by:
    (1) Using the retained activity rather than the activity
administered,
    (2) Using an occupancy factor less than 0.25 at 1 meter,
    (3) Using the biological or effective half-life, or
    (4) Considering the shielding by tissue.
    (d) The licensee shall maintain a record, for 3 years after the date
of release, that instructions were provided to a breast-feeding woman if
the radiation dose to the infant or child from continued breast-feeding
could result in a total effective dose equivalent exceeding 5
millisieverts (0.5 rem).

[62 FR 4133, Jan. 29, 1997]

REFERENCES:

(1) J Nucl Med 2001; Coover LR, et al. Therapeutic 131-I in outpatients: A simplified method conforming to the code of federal regulations, Tital 10, Part 35.75. 41: 1868-1875

(2) J Nucl Med 2001; de Klerk JMH. 131-I therapy: Inpatient or outpatient? 41: 1876-1878

(3) J Nucl Med 2012; Siberstein EB, et al. The SNNMI practice guideline for therapy of thyroid disease with 131I 3.0*. 53: 1633-1651

(4) Radiology 2014; Liu B, et al. Thyroid cancer: radiation safety precautions in 131I therapy based on actual biokinetic measures. 273: 211-219

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