The criteria used to evaluate/discern if an individual can be invited to participate in another research radiation study within the same year are:
- The regulatory status of the radioactive material (IND vs. RDRC).
For RDRC studies, there are specific organ dose limits that cannot be exceeded (FDA 21 CFR 361.1).
These limits are 3 rem per single administration and 5 rem per year to the radiosensitive organs (lens of eye, the gonads, red bone marrow and total body);and 5 rem per single administration and 15 rem per year to all other studies (such as the urinary bladder wall, kidney).
For non-RDRC studies, the above limits do NOT apply. However, we tend to keep them in mind when evaluating doses for "subjects in multiple studies" (known at the RSC as "SIMS).
- The sum effective dose from the combination of studies.
This is an internal NIH RSC guideline/policy that the total effective dose (ED) should be less than 5 rem per year. There are circumstances where a "SIMS" would be permitted to participate in studies where the total ED is greater than 5. However, there is a justification for a need to study the particular subject, and/or there is a possibility of direct subject benefit.
- Evaluating the sum total to the highest dosed organs.
As mentioned, we tend to use the RDRC organ dose limits as a guide for non-RDRC studies.
Example:
Protocol XX-X-0058 (RA # 1921, PI is Dr. F )
I-123 5-I-A-85380, 15 mCi/scan, max of 2 per year (under an IND)
Transmission scans
Effective Dose (ED) of 2.8 rem
Highest-dosed organs: Urinary bladder wall (UBW) = 8.0 rem, colon = 7.4 rem, LLI = 7.8 rem.
Protocol XX-X-0073 (RA # 1743, PI is Dr. C )
F-18 FP-TZTP, 10 mCi/scan, 1 per yr (under an IND)O-15 water, 40 mCi/scan, 1 per year
Transmission scans (2)
Effective Dose of 0.88 rem
Highest- dosed-organs: UBW = 2.73 rem, pancreas = 1.97 rem, kidney = 1.32 rem
For "SIMS" in both of above studies in same year:
Total effective dose is 3.68 rem (less than RSC guideline of 5 rem)
Highest-dosed organ is UBW = 10.73 rem (not a radiosensitive organ; less than 15 rem per year)
All other organs well within RDRC organ dose values (as stated in criteria #1)
Hence, subject may be invited to participate in both of these studies.
