In the area of therapeutic radiation oncology, administrations in the United States in 1992 were estimated to be associated with treatments for a total of 545,600 patients (as cited by Pollycove, 1993). Of these, 100,600 had byproduct teletherapy and 30,000 brachytherapy. The remaining 415,000 patients were treated with linear accelerator radiation therapy. Thus, the NRC regulatory apparatus is directed at misadministrations involving only about 25 percent of the total radiation therapy patients treated, and only about 0.026 percent of the total of all medication administrations in the United States per year (12 million out of 3.75 billion hospital medication administrations).
Patients receiving radiation therapy routinely receive multiple treatments. For purposes of calculating misadministration or error rates, the reasonable, but conservative, estimates of 20 treatments per teletherapy patient and 2 treatments per brachytherapy patient are used. This yields an annual administration rate of approximately 2 million. Using this figure, one can estimate the byproduct therapy misadministration rate at 0.002 percent (38 divided by 2,072,000, or about 2 per 100,000 administrations).
NRC-regulated states gave about one-third of the treatments. For these states, the estimated misadministration rate for byproduct therapy is 0.004 percent (21 divided by 690,667).
Nevertheless, lacking better data, the committee concluded that approximate rates of byproduct-related misadministrations for 1992 could be said to be:
for diagnostic misadministrations (Agreement States and NRC-regulated states combined), 0.00012 percent of all such administrations;
for diagnostic misadministrations (NRC-regulated states only), 0.0002 percent;
for therapeutic misadministrations (Agreement States and NRC-regulated states combined), 0.002 percent; and
for therapeutic misadministrations (NRC-regulated states only), 0.004 percent.
All these figures must be regarded as very rough approximations, for several reasons. No information is at hand on the degree of undercounting; the counts themselves are necessarily subject to statistical variation (the standard error of each is roughly the square root of the count); and the denominators are very crude estimates.4
It should be noted that the NRC-regulated states have been reporting misadministrations, pursuant to the QM rule (10 CFR 35.32) since January 1992. The Agreement States have only been required to do so since January 1995. Other than this fact, the committee has no explanation for the apparent discrepancy in these rates.