Answer to Question #3081 Submitted to "Ask the Experts"

In nuclear medicine, 99.5% of the procedures are diagnostic and are not associated with significant adverse effects. There are theoretical possibilities of slight increases of cancer from the low levels of radiation, but these are only theoretical, and many in the field do not believe that there are any deleterious effects at low levels. In addition, a significant body of literature supports claims of beneficial effects at low doses. So I would discount this as a "bad" side effect.

Therapeutic doses of Metastron and Quadramet for treating bone metastases from existing cancer can cause temporary bone marrow depression which reverts to the baseline, or nearly the baseline, levels in a matter of weeks or a couple of months. These effects are not noticed by the patient. In terminally ill patients the effects can be somewhat more severe, as their bone marrow contains significant quantities of tumors that have replaced marrow. These patients will shortly die of their underlying disease.

Doses of I-131 sodium iodide for hyperthyroidism are too low to cause any "bad" side effects. Doses on the order of 10 times higher, for the treatment of thyroid cancer, can cause bone marrow depression in patients with poor kidney function. Such patients need dialysis if they are treated. There may be some temporary effects on spermatogenesis at high doses. Common adverse effects characteristic of chemotherapy agents, such as loss of hair and nausea, vomiting, and diarrhea, do not occur with I-131. There may be an episode of nausea and/or vomiting a few hours after a large dose of I-131 sodium iodide due to stomach irritation. If it happens at all, it is usually only a single event, and can be avoided by the use of common antiemetics such as compazine.

Y-90-Zevalin and I-131-Bexxar, which are used to treat nonHodgkin's lymphoma, can cause considerable bone marrow depression requiring treatment, and there have been bleeding episodes, infections, and a few deaths. However, these are in patients who have received multiple regimens of chemotherapy for their cancer, and their bone marrow is vulnerable to begin with. These patients are generally followed closely by medical oncologists who treat any side effects that may occur.

Carol S. Marcus, PhD, MD
Professor of Radiation Oncology and of Radiological Sciences, UCLA, and
President, American College of Nuclear Physicians, California Chapter